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  • 251.
    Brett, Calvin
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Neutron and X-ray Surface Scattering Reveals the Morphology of Soft Matter Thin Films2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The last decades have been overshadowed by reports about the seemingly endless increase use of fossil-based resources. With the development of new products, our mindset is changing so that we more and more need to consider sustainability in our daily lives. Furthermore, smarter devices are indispensable in our world and daily life, and these are expected to be smaller and smaller in size.

    To support the transition from fossil-based to sustainable materials, we need to develop knowledge of new materials. Within this thesis project, the aim has been to understand the thin-film properties of sustainable materials and to develop methodologies to measure these. As sustainable template material wood-based nanocellulose was chosen as a bio-degradable representative with favourable favourable physical properties, such as lightweight, transparency, and flexibility. These properties make nanocellulose a perfect candidate for future advanced applications in thin-film organic solar cells, supercapacitors, or sensors. Nanocellulose comprises only a part of such a device, and hence the relevant functional materials and their combinations have to be studied to reveal the interaction between multiple material components on the final device performance. As the nanoscale, or even Ångstrom scale, governs the macroscopic physical properties, it is crucial to understand the materials in detail. Ergo, neutron and X-ray surface-sensitive scattering methods were applied to study nanoparticle deposition layering kinetics and the effects of environmental changes, which revealed the morphology of the resulting nanoporous nanocellulose thin films. The knowledge was used to infiltrate water-soluble intrinsic conductive polymers into these nanopores, which serves as a model for transparent but conductive templates for organic electronics. By changing the environment of the films through humidity cycling, the impact of the environment during a real-life application could be illustrated. Neutron scattering experiments also showed that the cellulose-conductive polymer composite (or hybridmaterial) changes irreversibly during humidity cycling while the pure nanocellulose films show fully reversible properties.

    Furthermore, the thermal decomposition of silver nitrate deposited on nanocellulose was studied to understand the nanofibrils' impact on the synthesis of nanoparticles. The transparency allowed in situ studies of the synthesis process, the spectroscopic properties as well as the plasmonic effect, which demonstrated routes for minimal material usage concepts for surface synthesis processes. It was also discovered that the process allows for band-gap tuning, which can be directly be applied in organic solar cells to tailor the band-gap to be adapted and hence increasing the efficiency.The morphological properties, as studied using X-rays and neutrons, were correlated to macroscopic properties by measuring wettability, surface topography, spectroscopy, or conductivity to examine the full materials application possibilities. Neutron and X-ray scattering methods are complementary and wisely combined, thus allowed pioneering studies of bio-based sustainable nanocomposites leading to advanced functional material concepts that support the development of devices using less fossil-based materials.

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  • 252.
    Brett, Calvin
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Deutsches Elektronen Synchrotron, Notkestraße 85, Hamburg, Germany.
    Forslund, Ola Kenji
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Nocerino, Elisabetta
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Kreuzer, L.P
    TU München, Germany.
    Widmann, T.
    TU München, Germany.
    Porcar, L.
    Institut Laue-Langevin, 71 Avenue des Martyrs, Grenoble, France.
    Yamada, N. L.
    High Energy Accelerator Research Organization (KEK), 203-1 Shirakata, Tokai, Naka 319-1106, Japan.
    Matsubara, Nami
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Müller-Buschbaum, P.
    TU München, Germany.
    Söderberg, Daniel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. Deutsches Elektronen Synchrotron, Notkestraße 85, Hamburg, Germany.
    Humidity-Induced Nanoscale Restructuring in PEDOT:PSS and Cellulose Nanofibrils Reinforced Biobased Organic Electronics2021In: Advanced Electronic Materials, E-ISSN 2199-160X, Vol. 7, no 6, p. 2100137-, article id 2100137Article in journal (Refereed)
    Abstract [en]

    In times where research focuses on the use of organic polymers as a base for complex organic electronic applications and improving device efficiencies, degradation is still less intensively addressed in fundamental studies. Hence, advanced neutron scattering methods are applied to investigate a model system for organic electronics composed of the widely used conductive polymer blend poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) together with nanocellulose as flexible reinforcing template material. In particular, the impact of relative humidity (RH) on the nanostructure evolution is studied in detail. The implications are discussed from a device performance point of view and the changing nanostructure is correlated with macroscale physical properties such as conductivity. The first humidification (95% RH) leads to an irreversible decrease of conductivity. After the first humidification cycle, however, the conductivity can be reversibly regained when returning to low humidity values (5% RH), which is important for device manufacturing. This finding can directly contribute to an improved usability of emerging organic electronics in daily live.

  • 253.
    Brett, Calvin
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Forslund, Ola Kenji
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Nocerino, Elisabetta
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Kreuzer, Lucas
    Wiedmann, Tobias
    Porcar, Lionel
    Yamada, Norifumi
    Matsubara, Nami
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Müller-Buschbaum, Peter
    Söderberg, Daniel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fiberprocesser.
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites.
    Humidity-induced Nanoscale Restructuring in PEDOT:PSS and Cellulose reinforced Bio-based Organic ElectronicsManuscript (preprint) (Other academic)
  • 254.
    Brett, Calvin J.
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. DESY, Notkestr 85, D-22607 Hamburg, Germany..
    Montani, Annaclaudia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering. Politecn Milan, Dept Chem Mat & Chem Engn Giulio Natta, Piazza Leonardo da Vinci 32, I-20133 Milan, Italy..
    Schwartzkopf, M.
    DESY, Notkestr 85, D-22607 Hamburg, Germany..
    van Benthem, R. A. T. M.
    Eindhoven Univ Technol, Lab Phys Chem SPC, Groene Loper 5, NL-5600 MB Eindhoven, Netherlands.;DSM Mat Sci Ctr, Urmonderbaan 22, NL-6167 RD Geleen, Netherlands..
    Jansen, J. F. G. A.
    DSM Mat Sci Ctr, Urmonderbaan 22, NL-6167 RD Geleen, Netherlands..
    Griffini, G.
    Politecn Milan, Dept Chem Mat & Chem Engn Giulio Natta, Piazza Leonardo da Vinci 32, I-20133 Milan, Italy..
    Roth, Stephan Volkher
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Johansson, Mats K.G.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology.
    Revealing structural evolution occurring from photo-initiated polymer network formation2020In: Communications Chemistry, E-ISSN 2399-3669, Vol. 3, no 1, article id 88Article in journal (Refereed)
    Abstract [en]

    Photopolymerization is a key enabling technology offering spatial and temporal control to allow for future functional materials to be made to meet societal needs. However, gaining access to robust experimental techniques to describe the evolution of nanoscale morphology in photo-initiated polymeric systems has proven so far to be a challenging task. Here, we show that these physical transformations can be monitored and quantified at the nanoscale in situ and in real-time. It is demonstrated that the initial structural features of the liquid precursors significantly affect the final morphology and the physical properties of the resulting solid via the occurrence of local heterogeneities in the molecular mobility during the curing transformation. We have made visible how local physical arrestings in the liquid, associated with both cross-linking and vitrification, determine the length scale of the local heterogeneities forming upon curing, found to be in the 10-200nm range. Acomplete account of the structural evolution occurring during photopolymerisation is lacking. Here the physical changes occurring on the nanometer scale during photopolymerisation of acrylates are followed over time by FTIR, X-ray reflectometry, AFM, and GISAXS, offering insight into the mechanism by which initial composition influences the final morphology.

  • 255.
    Brett, Calvin
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Deutsches Elektronen-Synchrotron DESY, Hamburg 22607, Germany.
    Mittal, Nitesh
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Mechanics.
    Ohm, Wiebke
    Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, 22607, Hamburg, Germany.
    Gensch, Marc
    Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, 22607, Hamburg, Germany.
    Kreuzer, Lucas P.
    Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, 22607, Hamburg, Germany.
    Körstgens, Volker
    Lehrstuhl für Funktionelle Materialien, Physik-Department, and ¶ Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universitat ̈ München, Garching 85748, Germany.
    Månsson, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Frielinghaus, Henrich
    Jülich Centre for Neutron Science at MLZ.
    Söderberg, Daniel
    KTH, Superseded Departments (pre-2005), Mechanics. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites. Deutsches Elektronen-Synchrotron DESY, Hamburg 22607, Germany.
    Water-Induced Structural Rearrangements on the Nanoscale in Ultrathin Nanocellulose Films2019In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 52, no 12, p. 4721-4728Article in journal (Refereed)
    Abstract [en]

    Many nanoscale biopolymer building blocks with defect-free molecular structure and exceptional mechanical properties have the potential to surpass the performance of existing fossil-based materials with respect to barrier properties, load-bearing substrates for advanced functionalities, as well as light-weight construction. Comprehension and control of performance variations of macroscopic biopolymer materials caused by humidity-driven structural changes at the nanoscale are imperative and challenging. A long-lasting challenge is the interaction with water molecules causing reversible changes in the intrinsic molecular structures that adversely affects the macroscale performance. Using in situ advanced X-ray and neutron scattering techniques, we reveal the structural rearrangements at the nanoscale in ultrathin nanocellulose films with humidity variations. These reversible rearrangements are then correlated with wettability that can be tuned. The results and methodology have general implications not only on the performance of cellulose-based materials but also for hierarchical materials fabricated with other organic and inorganic moisture-sensitive building blocks.

  • 256.
    Brett, Calvin
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Forschungszentrum Helmholtz Gemeinschaft, Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany.
    Ohm, Wiebke
    Forschungszentrum Helmholtz Gemeinschaft, Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany..
    Fricke, Bjorn
    Forschungszentrum Helmholtz Gemeinschaft, Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany..
    Alexakis, Alexandros Efraim
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Laarmann, Tim
    Forschungszentrum Helmholtz Gemeinschaft, Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany.;Hamburg Ctr Ultrafast Imaging CUI, D-22761 Hamburg, Germany..
    Korstgens, Volker
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Materialien, D-85748 Garching, Germany..
    Muller-Buschbaum, Peter
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Materialien, D-85748 Garching, Germany.;Tech Univ Munich, Heinz Maier Leibnitz Zentrum MLZ, D-85748 Garching, Germany..
    Söderberg, Daniel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fiberprocesser.
    Roth, Stephan, V
    Forschungszentrum Helmholtz Gemeinschaft, Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany.;Dept Fibre & Polymer Technol, Div Coating Technol, S-10044 Stockholm, Sweden..
    Nanocellulose-Assisted Thermally Induced Growth of Silver Nanoparticles for Optical Applications2021In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 13, no 23, p. 27696-27704Article in journal (Refereed)
    Abstract [en]

    Optically responsive materials are present in everyday life, from screens to sensors. However, fabricating large-area, fossil-free materials for functional biocompatible applications is still a challenge today. Nanocelluloses from various sources, such as wood, can provide biocompatibility and are emerging candidates for templating organic optoelectronics. Silver (Ag) in its nanoscale form shows excellent optical properties. Herein, we combine both materials using thin-film large-area spray-coating to study the fabrication of optical response applications. We characterize the Ag nanoparticle formation by X-ray scattering and UV-vis spectroscopy in situ during growth on the nanocellulose template. The morphology and optical properties of the nanocellulose film are compared to the rigid reference surface SiO2. Our results clearly show the potential to tailor the energy band gap of the resulting hybrid material.

  • 257.
    Brett, Calvin
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Ohm, Wiebke
    Fricke, Björn
    Laarmann, Tim
    Körstgens, Volker
    Müller-Buschbaum, Peter
    Söderberg, Daniel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fiberprocesser.
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites.
    Nanocellulose-Assisted Thermally-Induced Growth of Silver Nanoparticles for Optical ApplicationsManuscript (preprint) (Other academic)
  • 258.
    Brito, Pedro P. C.
    et al.
    Inst Tecnol Aeronaut, Aerodynam Dept, Sao Jose Dos Campos, Brazil..
    Morra, Pierluigi
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Stability, Transition and Control. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Cavalieri, Andre V. G.
    Inst Tecnol Aeronaut, Aerodynam Dept, Sao Jose Dos Campos, Brazil..
    Araujo, Tiago B.
    Inst Tecnol Aeronaut, Aerodynam Dept, Sao Jose Dos Campos, Brazil..
    Henningson, Dan S.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Stability, Transition and Control. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Hanifi, Ardeshir
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Experimental control of Tollmien-Schlichting waves using pressure sensors and plasma actuators2021In: Experiments in Fluids, ISSN 0723-4864, E-ISSN 1432-1114, Vol. 62, no 2, article id 32Article in journal (Refereed)
    Abstract [en]

    This manuscript presents a successful application of the inverse feed-forward control (IFFC) technique for control of the Tollmien-Schlichting (TS) waves over a wing profile placed in an open-circuit wind tunnel. Active cancellation of two-dimensional broadband TS disturbances is performed using a single dielectric barrier discharge (DBD) plasma actuator. The measurements required for the IFFC are performed with microphones, instead of hot wires often used for this purpose, in order to reduce the space occupied by the sensors and assess the suitability of simpler and cheaper devices. An attenuation of the TS-wave amplitude of one order of magnitude is achieved. Direct numerical simulations (DNS) are also performed and compared to the outcome of the experiments. The plasma-actuator model used in DNS is a mapping of the force field used by Fabbiane et al. (In: Proceedings of TSFP-9, Melbourne, 2015a) to the actual geometry, whereas the sensors (microphones) are modeled as pressure probes. Despite these modelling choices, a good agreement between the results of DNS and the experiments is achieved. However, the control performance is better in the DNS, with attenuation of three orders of magnitude of TS-wave amplitude. Further analysis of experiments and simulations shows that the limiting factor in the experiments is the ambient low-frequency acoustic waves in the wind tunnel. These waves are sensed by the microphones and act as noise in the analysis of TS-wave evolution and thus leading to lower coherence between sensors and actuators. This in turn leads to a suboptimal control kernel in the experiment.Please confirm if the inserted city and country are correct in Affiliations [Aff1, Aff2]. Amend if necessary.Confirmed. It is correct.Please confirm if the corresponding author is correctly identified. Amend if necessary.Confirmed. The corresponding author is Pedro P. C. Brito.

  • 259.
    Brizzolara, Stefano
    et al.
    Institute of Environmental Engineering, ETH Zurich, CH-8039 Zürich, Switzerland; Swiss Federal Institute of Forest, Snow and Landscape Research WSL, Birmensdorf, 8903, Switzerland..
    Rosti, Marco E.
    Complex Fluids and Flows Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan..
    Olivieri, Stefano
    Complex Fluids and Flows Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan; DICCA, University of Genova and INFN, Genova Section, Via Montallegro 1, Genova, 16145, Italy..
    Brandt, Luca
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Holzner, Markus
    Swiss Federal Institute of Forest, Snow and Landscape Research WSL, Birmensdorf, 8903, Switzerland; Swiss Federal Institute of Aquatic Science and Technology Eawag, 8600 Dübendorf, Switzerland..
    Mazzino, Andrea
    DICCA, University of Genova and INFN, Genova Section, Via Montallegro 1, Genova, 16145, Italy.
    Fiber Tracking Velocimetry for Two-Point Statistics of Turbulence2021In: Physical Review X, E-ISSN 2160-3308, Vol. 11, no 3, article id 031060Article in journal (Refereed)
    Abstract [en]

    We propose and validate a novel experimental technique to measure two-point statistics of turbulent flows. It consists of spreading rigid fibers in the flow and tracking their position and orientation in time and is therefore named “fiber tracking velocimetry.” By choosing different fiber lengths, i.e., within the inertial or dissipative range of scales, the statistics of turbulence fluctuations at the selected length scale can be probed accurately by simply measuring the fiber velocity at its two ends and projecting it along the transverse-to-fiber direction. By means of fully resolved direct numerical simulations and experiments, we show that these fiber-based transverse velocity increments are statistically equivalent to the (unperturbed) flow transverse velocity increments. Moreover, we show that the turbulent energy-dissipation rate can be accurately measured exploiting sufficiently short fibers. The technique is tested against standard particle tracking velocimetry (PTV) of flow tracers with excellent agreement. Our technique overcomes the well-known problem of PTV to probe two-point statistics reliably because of the fast relative diffusion in turbulence that prevents the mutual distance between particles to remain constant at the length scale of interest. This problem, making it difficult to obtain converged statistics for a fixed separation distance, is even more dramatic for natural flows in open domains. A prominent example is oceanic currents, where drifters (i.e., the tracer-particle counterpart used in field measurements) disperse quickly, but at the same time their number has to be limited to save costs. Inspired by our laboratory experiments, we propose pairs of connected drifters as a viable option to solve the issue.

  • 260.
    Brodén, Erik
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Väg- och spårfordon samt konceptuell fordonsdesign.
    Wheel Wear and Reprofiling Alternatives for Swedish Rc4 Locomotive – Measurements and Simulations2006Independent thesis Advanced level (degree of Master of Fine Arts (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Railway wheels have to be reprofiled or replaced if they do not fulfil certain demands and the costs for these actions can be considerable for the vehicle owner. The purpose of this work is to study wheel profiles at reprofiling through wheel wear simulations and reprofiling statistics.

    The application at hand is the Rc4 locomotive used by the railway freight company Green Cargo. The locomotives travel the whole electrified Swedish railway network but a large part of the traffic is on the lines Malmö-Hallsberg and Luleå-Ockelbo. For these two lines the distributions of curve radius, track quality and lubrication have been analysed.

    The simulation method is based on a load collective concept where the load collective is a discretization of actual conditions such as track design geometry, rail profiles, track irregularities, lubrication, vehicle speed and traction. The discretization results in a number of dynamic time-domain simulations to be performed in each wear step. The time-domain simulations are done with the MBS (Multi-Body-Simulation) tool Gensys. From these simulations the wear is calculated with a program developed in MATLAB, the wheel profile is updated and the next wear step is entered. In the vehicle-track simulations the wheel-rail contact is modelled with the Hertzian theory for the normal contact and Kalker’s simplified theory for the tangential forces. Archard’s wear equation together with wear coefficients have been used to calculate the material worn off from the wheel. The wear coefficients have been determined from dry conditions and to compensate for both natural and manmade lubrication two scaling factors are used.Reprofiling of wheels on the Rc4 locomotive is done in two workshops and wheel profiles and wheel lathe differs between these two workshops. At assembling of new wheels the wheels have the UIC/ORE S1002 profile with flange thickness 32.5 mm but in order to save wheel diameter at reprofiling two different profiles with smaller flange thickness are used. From a wheelset database used by Green Cargo for maintenance planning statistics such as distribution of reprofiling causes, seasonal variations of wheel wear and damages, running distances, life length of wheels and wear rates for different profiles have been extracted.

    For evaluation purposes wheel profiles of three locomotives were measured before and after the first reprofiling. When comparing measured and simulated wheel profiles it can be concluded that the simulation overestimates flange wear somewhat but the shape of the flange is close to measurements. Wheel tread wear is generally well predicted but the shape differs more. The simulation results are also compared, with good agreement, to simple measurements of wheel wear scalars from the wheelset database. For some wheel profiles problems in the simulations with unrealistic cavities at the wheel tread remain to be solved.Through simulations it has been seen that with a slight change of one of the profiles used at reprofiling running distance before reprofiling due to thin flanges can be increased with 95 kkm.

  • 261.
    Brouillette, Elise
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Structural temperatures of wind turbine blades under icing conditions2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As clean energy demand is on the rise and the wind energy sector in growth, locations with the highest wind potential are becoming of higher interest for wind farm projects, but they are located in colder regions. In cold climates, ice accumulation on wind turbine blades is a serious issue, both in terms of safety and performance. To prevent this, anti-icing technologies, such as Vestas Wind Systems A/S’s, electro-thermal elements are added to wind turbine blades’ construction. This thesis project consists of developing a method to investigate the heat transfer inside and out of wind turbine blades to assess the performance of the anti-icing system and most importantly, verify if it could lead to thermal damage of the blade’s adhesive. In an integrated MATLAB code, the heating requirement is calculated and the 2D conduction modelled based on the wind conditions. The output is a temperature map of the internal structure along with the points with the highest temperature for all adhesive locations, which shows that the selected heating power provided by the heating elements compromises the integrity of the adhesive and doesn’t perform to allow the surface temperature to reach the necessary threshold the prevent icing.

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    fulltext
  • 262.
    Buckler, Andrew J.
    et al.
    Karolinska Inst, Dept Mol Med & Surg, Stockholm, Sweden.;Elucid Bioimaging Inc, Boston, MA USA..
    Karlof, Eva
    Karolinska Inst, Dept Mol Med & Surg, Stockholm, Sweden..
    Lengquist, Mariette
    Karolinska Inst, Dept Mol Med & Surg, Stockholm, Sweden.;Karolinska Inst, Dept Med Solna, Stockholm, Sweden..
    Gasser, T. Christian
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Maegdefessel, Lars
    Perisic Matic, Ljubica
    Karolinska Inst, Dept Mol Med & Surg, Stockholm, Sweden..
    Hedin, Ulf
    Karolinska Inst, Dept Mol Med & Surg, Stockholm, Sweden..
    Virtual Transcriptomics Noninvasive Phenotyping of Atherosclerosis by Decoding Plaque Biology From Computed Tomography Angiography Imaging2021In: Arteriosclerosis, Thrombosis and Vascular Biology, ISSN 1079-5642, E-ISSN 1524-4636, Vol. 41, no 5, p. 1738-1750Article in journal (Refereed)
    Abstract [en]

    Objective: Therapeutic advancements in atherosclerotic cardiovascular disease have improved prevention of ischemic stroke and myocardial infarction, but diagnostic methods for atherosclerotic plaque phenotyping to aid individualized therapy are lacking. In this feasibility study, we aimed to elucidate plaque biology by decoding the molecular phenotype of plaques through analysis of computed-tomography angiography images, making a predictive model for plaque biology referred to as virtual transcriptomics. Approach and Results: We employed machine intelligence using paired computed-tomography angiography and transcriptomics from carotid endarterectomies of 40 patients undergoing stroke-preventive surgery for carotid stenosis. Computed tomography angiographies were analyzed with novel software for accurate characterization of plaque morphology and plaque transcriptomes obtained from microarrays, followed by mathematical modeling for prediction of molecular signatures. Four hundred fourteen coding and noncoding RNAs were robustly predicted using supervised models to estimate gene expression based on plaque morphology. Examples of predicted transcripts included ion transporters, cytokine receptors, and a number of microRNAs whereas pathway analyses demonstrated enrichment of several biological processes relevant for the pathophysiology of atherosclerosis and plaque instability. Finally, the ability of the models to predict plaque gene expression was demonstrated using computed tomography angiographies from 4 sequestered patients and comparisons with transcriptomes of corresponding lesions. Conclusions: The results of this pilot study show that atherosclerotic plaque phenotyping by image analysis of conventional computed-tomography angiography can elucidate the molecular signature of atherosclerotic lesions in a multiscale setting. The study holds promise for optimized personalized therapy in the prevention of myocardial infarction and ischemic stroke, which warrants further investigations in larger cohorts.

  • 263.
    Buckler, Andrew J.
    et al.
    Karolinska Inst, Dept Mol Med & Surg, Stockholm, Sweden.;Elucid Bioimaging Inc, Boston, MA USA..
    van Wanrooij, Max
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Andersson, Måns
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Karlof, Eva
    Karolinska Inst, Dept Mol Med & Surg, Stockholm, Sweden..
    Matic, Ljubica Perisic
    Karolinska Inst, Dept Mol Med & Surg, Stockholm, Sweden..
    Hedin, Ulf
    Karolinska Inst, Dept Mol Med & Surg, Stockholm, Sweden..
    Gasser, T. Christian
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics. Univ Southern Denmark, Fac Hlth Sci, Odense, Denmark..
    Patient-specific biomechanical analysis of atherosclerotic plaques enabled by histologically validated tissue characterization from computed tomography angiography: A case study2022In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 134, article id 105403Article in journal (Refereed)
    Abstract [en]

    Background: Rupture of unstable atherosclerotic plaques with a large lipid-rich necrotic core and a thin fibrous cap cause myocardial infarction and stroke. Yet it has not been possible to assess this for individual patients. Clinical guidelines still rely on use of luminal narrowing, a poor indicator but one that persists for lack of effective means to do better. We present a case study demonstrating the assessment of biomechanical indices pertaining to plaque rupture risk non-invasively for individual patients enabled by histologically validated tissue characterization. Methods: Routinely acquired clinical images of plaques were analyzed to characterize vascular wall tissues using software validated by histology (ElucidVivo, Elucid Bioimaging Inc.). Based on the tissue distribution, wall stress and strain were then calculated at spatial locations with varied fibrous cap thicknesses at diastolic, mean and systolic blood pressures. Results: The von Mises stress of 152 [131, 172] kPa and the equivalent strain of 0.10 [0.08, 0.12] were calculated where the fibrous cap thickness was smallest (560 mu m) (95% CI in brackets). The stress at this location was at a level predictive of plaque failure. Stress and strain at locations with larger cap thicknesses were calculated to be lower, demonstrating a clinically relevant range of risk levels. Conclusion: Patient specific tissue characterization can identify distributions of stress and strain in a clinically relevant range. This capability may be used to identify high-risk lesions and personalize treatment decisions for individual patients with cardiovascular disease and improve prevention of myocardial infarction and stroke.

  • 264.
    Buist, Mirka
    et al.
    Ctr Bion & Pain Res, S-43180 Mölndal, Sweden.;Bion Inst, Melbourne, Vic 3002, Australia.;Univ Gothenburg, Inst Physiol & Neurosci, Sahlgrenska Acad, Dept Physiol, S-41390 Gothenburg, Sweden..
    Damercheli, Shahrzad
    Ctr Bion & Pain Res, S-43180 Mölndal, Sweden.;Chalmers Univ Technol, Dept Elect Engn, S-41296 Gothenburg, Sweden..
    Truong, Minh Tat Nhat
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics. Ctr Bion & Pain Res, S-43180 Mölndal, Sweden.
    Sanna, Alessio
    Ctr Bion & Pain Res, S-43180 Mölndal, Sweden..
    Mastinu, Enzo
    Ctr Bion & Pain Res, S-43180 Mölndal, Sweden.;Chalmers Univ Technol, Dept Elect Engn, S-41296 Gothenburg, Sweden.;St Anna Sch Adv Studies, BioRobot Inst, Artificial Hands Area, I-56025 Pontedera, Italy..
    Ortiz-Catalan, Max
    Ctr Bion & Pain Res, S-43180 Mölndal, Sweden.;Bion Inst, Melbourne, Vic 3002, Australia.;Chalmers Univ Technol, Dept Elect Engn, S-41296 Gothenburg, Sweden..
    Development and Validation of a Wearable Device to Provide Rich Somatosensory Stimulation for Rehabilitation After Sensorimotor Impairment2023In: IEEE Transactions on Biomedical Circuits and Systems, ISSN 1932-4545, E-ISSN 1940-9990, Vol. 17, no 3, p. 547-557Article in journal (Refereed)
    Abstract [en]

    Training sensory discrimination of the skin has the potential to reduce chronic pain due to sensorimotor impairments and increase sensorimotor function. Currently, there is no such device that can systematically provide rich skin stimulation suitable for a training protocol for individuals with amputation or major sensory impairment. This study describes the development and validation of a non-invasive wearable device meant to repeatedly and safely deliver somatosensory stimulations. The development was guided by a structured design control process to ensure the verifiability and validity of the design outcomes. Two sub-systems were designed: 1) a tactile display for touch and vibration sensations, and 2) a set of bands for sliding, pressure, and strain sensations. The device was designed with a versatile structure that allows for its application on different body parts. We designed a device-paired interactive computer program to enable structured sensory training sessions. Validation was performed with 11 individuals with intact limbs whose upper arm tactile sensitivity was measured over 5 training sessions. Tactile discrimination and perception threshold were measured using the standard 2-point discrimination and Semmes-Weinstein monofilament tests, respectively. The results of the monofilament test showed a significant improvement (p = 0.011), but the improvement was not significant for the 2-point discrimination test(p = 0.141). These promising results confirm the potential of the proposed training to increase the sensory acuity in the upper arms of individuals with intact limbs. Further studies will be conducted to determine how to transfer the findings of this work to improve the pain and/or functional rehabilitation in individuals with sensorimotor impairments.

  • 265.
    Buist, Mirka
    et al.
    Sahlgrens Univ Hosp, Ctr Adv Reconstruct Extrem CARE, S-43180 Mölndal, Sweden.;Bion Inst, Melbourne, Vic 3002, Australia.;Univ Melbourne, Med Bion Dept, Fitzroy, Vic 3065, Australia.;NeuroBioniX, Melbourne, Vic 3065, Australia..
    Damercheli, Shahrzad
    Chalmers Univ Technol, Dept Elect Engn, S-41296 Gothenburg, Sweden.;Chalmers Univ Technol, Dept Microtechnol & Nanosci, S-41296 Gothenburg, Sweden..
    Zbinden, Jan
    Chalmers Univ Technol, Dept Elect Engn, S-41296 Gothenburg, Sweden..
    Truong, Minh Tat Nhat
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics.
    Mastinu, Enzo
    Chalmers Univ Technol, Dept Elect Engn, S-41296 Gothenburg, Sweden..
    Ortiz-Catalan, Max
    Bion Inst, Melbourne, Vic 3002, Australia.;Univ Melbourne, Med Bion Dept, Fitzroy, Vic 3065, Australia.;NeuroBioniX, Melbourne, Vic 3065, Australia.;Prometei Pain Rehabil Ctr, UA-21018 Vinnytsia, Ukraine..
    Novel Wearable Device for Mindful Sensorimotor Training: Integrating Motor Decoding and Somatosensory Stimulation for Neurorehabilitation2024In: IEEE transactions on neural systems and rehabilitation engineering, ISSN 1534-4320, E-ISSN 1558-0210, Vol. 32, p. 1515-1523Article in journal (Refereed)
    Abstract [en]

    Sensorimotor impairment is a prevalent condition requiring effective rehabilitation strategies. This study introduces a novel wearable device for Mindful Sensorimotor Training (MiSMT) designed for sensory and motor rehabilitation. Our MiSMT device combines motor training using myoelectric pattern recognition along sensory training using two tactile displays. This device offers a comprehensive solution, integrating electromyography and haptic feedback, lacking in existing devices. The device features eight electromyography channels, a rechargeable battery, and wireless Bluetooth or Wi-Fi connectivity for seamless communication with a computer or mobile device. Its flexible material allows for adaptability to various body parts, ensuring ease of use in diverse patients. The two tactile displays, with 16 electromagnetic actuators each, provide touch and vibration sensations up to 250 Hz. In this proof-of-concept study, we show improved two-point discrimination after 5 training sessions in participants with intact limbs (p=0.047). We also demonstrated successful acquisition, processing, and decoding of myoelectric signals in offline and online evaluations. In conclusion, the MiSMT device presents a promising tool for sensorimotor rehabilitation by combining motor execution and sensory training benefits. Further studies are required to assess its effectiveness in individuals with sensorimotor impairments. Integrating mindful sensory and motor training with innovative technology can enhance rehabilitation outcomes and improve the quality of life for those with sensorimotor impairments.

  • 266.
    Burman, Gustav
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Lightweight Structures.
    Enhancing the endurance of UAVs by the use of structural power composites: System-level study of a flying wing2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis studies the feasibility of integrating the novelStructural Battery (SB)[1] into the airframe of a UnmannedAerial Vehicle (UAV). The potential advantages in terms ofmass, range and endurance are studied.The aircraft performance is analysed using conventionalflight mechanics, modelled in Matlab and Xfoil. The structureis designed and analysed using composite laminate theoryand beam theory in conjunction with verification in AnsysMechanical. An iterative procedure was used to arriveat a design that satisfied the set structural- and flight requirements.The currently demonstrated structural battery has a specificenergy density of 23.8Wh/kg, an elastic modulus of25GPa and tensile strength of at least 300MPa.[1]The laminae properties used in this master thesis were estimatedusing the Reuss and Voigt model combined with theRule of Mixtures (RoM). A quasi isotropic SB laminate wasmodelled according to the previous structural requirementsand assumed material properties. It yielded an elastic modulusof 54GPa. In order to simplify the analysis the energyand stiffness were decoupled. The SB was assigned a specificenergy of 23.8Wh/kg and 60.6Wh/kg according to thevalues measured and estimated previously[1].A SB with a tensile modulus of 54GPa and specific energyof 24Wh/kg was shown not to be beneficial to integrate intothe primary aircraft structure. The designed SB yieldeda reduction in flight range of 5.8%. This was shown bycomparing the designed SB with a reference aircraft configuration.The reference configuration uses a conventionalbattery that has a specific energy density of 160Wh/kg andconventional Carbon Fibre Composite (CFC) with an elasticmodulus of 71GPa.It was shown that the integration of the SB modelled wouldbecome beneficial compared to the reference aircraft configurationwhen the SB specific energy exceeds 33Wh/kg.The integration of a structural battery with a specific energyof 60.6Wh/kg yielded a flight range improvement of16.9% compared to the reference aircraft.

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  • 267.
    Buscariolo, Filipe F.
    et al.
    Imperial Coll London, Dept Aeronaut, London SW7 2AZ, England.;McLaren Racing, CFD Methodol Grp, Woking, Surrey, England.;Univ Sao Paulo, Nucleo Dinam & Fluidos Res Grp, Sao Paulo, Brazil..
    Hoessler, Julien
    McLaren Racing, CFD Methodol Grp, Woking, Surrey, England..
    Moxey, David
    Kings Coll London, Dept Engn, London, England..
    Jassim, Ayad
    Hewlett Packard Enterprise, SGI, Reading, Berks, England..
    Gouder, Kevin
    Imperial Coll London, Dept Aeronaut, London SW7 2AZ, England..
    Basley, Jeremy
    Imperial Coll London, Dept Aeronaut, London SW7 2AZ, England..
    Murai, Yushi
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics, Fluid Physics.
    Assi, Gustavo R. S.
    Univ Sao Paulo, Nucleo Dinam & Fluidos Res Grp, Sao Paulo, Brazil..
    Sherwin, Spencer J.
    Imperial Coll London, Dept Aeronaut, London SW7 2AZ, England..
    Spectral/hp element simulation of flow past a Formula One front wing: Validation against experiments2022In: Journal of Wind Engineering and Industrial Aerodynamics, ISSN 0167-6105, E-ISSN 1872-8197, Vol. 221, article id 104832Article in journal (Refereed)
    Abstract [en]

    Emerging commercial and academic tools are regularly being applied to the design of road and race cars, but there currently are no well-established benchmark cases to study the aerodynamics of race car wings in ground effect. In this paper we propose a new test case, with a relatively complex geometry, supported by the availability of CAD model and experimental results. We refer to the test case as the Imperial Front Wing, originally based on the front wing and endplate design of the McLaren 17D race car. A comparison of different resolutions of a high fidelity spectral/hp element simulation using under-resolved DNS/implicit LES approach with fourth and fifth polynomial order is presented. The results demonstrate good correlation to both the wall-bounded streaklines obtained by oil flow visualization and experimental PIV results, correctly predicting key characteristics of the time-averaged flow structures, namely intensity, contours and locations. This study highlights the resolution requirements in capturing salient flow features arising from this type of challenging geometry, providing an interesting test case for both traditional and emerging high-fidelity simulations.

  • 268.
    Bäbler, Matthäus
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes.
    Biferale, Luca
    Brandt, Luca
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Feudel, Ulrike
    Theoretical Physics, Complex Systems, ICBM, University of Oldenburg, Oldenburg, Germany.
    Guseva, Ksenia
    Theoretical Physics, Complex Systems, ICBM, University of Oldenburg, Oldenburg, Germany.
    Lanotte, A. S.
    Marchioli, C.
    Pecile, Eros
    University of Udine, Udine, Italy.
    Picano, Francesco
    University of Udine, Udine, Italy.
    Sardina, Gaetano
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Soldati, Alfredo
    University of Udine, Udine, Italy.
    Toschi, Federico
    Dept. Applied Physics, Eindhoven University of Technology, Eindhoven, Netherlands.
    Breakup of small aggregates in bounded and unbounded turbulent flows2020In: ETC 2013 - 14th European Turbulence Conference, Zakon Group LLC , 2020Conference paper (Refereed)
    Abstract [en]

    Breakup of small tracer-like aggregates is studied by means of numerical simulations in four different flows, namely homogeneous isotropic turbulence, smooth stochastic flow, turbulent channel flow, and developing boundary layer flow. Aggregate breakup occurs when the local hydrodynamic stress σ ∼ ε1/2, where ε is the local energy dissipation, overcomes a given threshold value σcr [or equivalently εcr ∼ σcr2 ] characteristic for a given type of aggregates. Following the aggregate trajectory upon release and detecting the first occurrence of local energy dissipation exceeding the predefined threshold allows for estimating the breakup rate as a function of εcr. Results show that the breakup rate decreases with increasing threshold. For small values of the threshold, this decrease assumes consistent scaling among the different flows which is explained by universal small scale flow properties. 

  • 269.
    Caddy, Harrison T.
    et al.
    Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia and the UWA Centre for Medical Research, The University of Western Australia, Perth, WA, Australia; School of Human Sciences (Exercise and Sport Sciences), The University of Western Australia, Perth, WA, Australia.
    Kelsey, Lachlan J.
    Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia and the UWA Centre for Medical Research, The University of Western Australia, Perth, WA, Australia; School of Engineering, The University of Western Australia, Perth, WA, Australia.
    Parker, Louis P.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Green, Daniel J.
    School of Human Sciences (Exercise and Sport Sciences), The University of Western Australia, Perth, WA, Australia.
    Doyle, Barry J.
    Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia and the UWA Centre for Medical Research, The University of Western Australia, Perth, WA, Australia; School of Engineering, The University of Western Australia, Perth, WA, Australia.
    Modelling large scale artery haemodynamics from the heart to the eye in response to simulated microgravity2024In: npj Microgravity, E-ISSN 2373-8065, Vol. 10, no 1, article id 7Article in journal (Refereed)
    Abstract [en]

    We investigated variations in haemodynamics in response to simulated microgravity across a semi-subject-specific three-dimensional (3D) continuous arterial network connecting the heart to the eye using computational fluid dynamics (CFD) simulations. Using this model we simulated pulsatile blood flow in an upright Earth gravity case and a simulated microgravity case. Under simulated microgravity, regional time-averaged wall shear stress (TAWSS) increased and oscillatory shear index (OSI) decreased in upper body arteries, whilst the opposite was observed in the lower body. Between cases, uniform changes in TAWSS and OSI were found in the retina across diameters. This work demonstrates that 3D CFD simulations can be performed across continuously connected networks of small and large arteries. Simulated results exhibited similarities to low dimensional spaceflight simulations and measured data—specifically that blood flow and shear stress decrease towards the lower limbs and increase towards the cerebrovasculature and eyes in response to simulated microgravity, relative to an upright position in Earth gravity.

  • 270.
    Caffier, Erwan
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Space Technology.
    Mission Planning for the in-orbit Lunar calibrations of the MicroCarb instrument2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In-orbit calibrations of space instruments are often necessary to ensure the accuracy of the measurements. The Moon provides a target with very predictable characteristics. In this report, the opportunities to perform in-orbit lunar calibrations of the MicroCarb instrument are evaluated and a procedure for conducting the Mission Planning for these calibrations is developed. Through modeling the spacecraft in its orbit, simulations show that continuous observation sequences of up to 48 minutes can be expected each lunation. The variability of the optical properties of the Moon during an opportunity is related to the orientation of the plane of the orbit of the spacecraft with respect to the cone with axis the Moon-Sun direction and apex the center of the Moon that contains the spacecraft. Choosing a value of the phase angle (Sun-Moon-Spacecraft angle) around −20 degrees to plan the lunar calibrations allows to minimize the variations of apparent radiance of the Moon during the observation. The results make it possible to refine the choice of the best moments to plan the lunar calibrations. This also allows the satellite operations team to anticipate the planning of lunar calibrations on the scale of several months.

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  • 271.
    Calen, Titus
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics, Technical Acoustics.
    Wang, Xiaomo
    Simulation of Complex Sound Radiation Patterns from Truck Components using Monopole Clusters2023Independent thesis Advanced level (degree of Master of Fine Arts (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Pass-by noise testing is an important step in vehicle design and regulation compliance. Finite element analysis simulations have been used to cut costs on prototyping and testing, but the high computational cost of simulating surface vibrations from complex geometries and the resulting airborne noise propagation is making the switch to digital twin methods not viable. This paper aims at investigating the use of equivalent source methods as an alternative to the before mentioned simulations. Through the use of a simple 2D model, the difficulties such as ill-conditioning of the transfer matrix and the required regularisation techniques such as TSVD and the Tikhonov L-curve method are tested and then applied to a mesh of a 3D engine model. Source and pressure field errors are measured and their origins are explained. A heavy emphasis is put on the model geometry as a source of error. Finally, rules of thumb based on the regularisation balance and the wavelength dependent pressure sampling positions are formulated in order to achieve usable results.

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  • 272.
    Calzolari, Giovanni
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    CFD study and method development for air intake systems using OpenFOAM2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report is the result of a joint collaboration between the two Swedish companies AFRY and Scania AB. The need of CFD analyses for internal flow purposes are continuously increasing in companies like Scania. However the use of CFD software is limited to license costs. The objective and idea of this thesis is to esablish whether OpenFOAM, an open-source CFD software, could be a suitable alternative to the currently used CFD commercial software StarCCM+ when performing total pressure drops analysis on air intake systems. Furthermore, a second objective is to develop a standard method to analyze this class of systems using OpenFOAM. Air intake systems play a significant role in the efficiency of the engine of a bus or a truck, being responsible to drive clean fresh air to the engine with the minimum amount of pressure drops.

    After an illustrative introduction of the topic and theory principles, the following technical analysis focuses first on a CFD study of the simple Buice and Eaton 2D diffuser, to primarily benchmark OpenFOAM, StarCCM+ and the experimental data in a turbulence models and a mesh independence analyses. For both software the turbulence model RNG k − ε fails almost entirely to detect the separation and wide re-circulation bubble formed in the diffuser, while k − ω SST, being not much more computationally expensive, gives very accurate results. For these reasons, even the velocity profiles, pressure coefficient and skin friction coefficient plots analyzed with RNG k − ε turbulence model show larger discrepancy compared to the experimental data. 

    Secondly, a total pressure drop CFD study of the Scania air intake system follows. Performing multiple simulations for a range of different mass flow rates, both OpenFOAM and StarCCM+ show very good agreement with the experimental data. This time, due to the lack of big separation zones in the system, k − ω SST and RNG k − ε perform quite similarly, the therefore k − ε relative inexpensiveness in this more complex and heavy system makes the latter the most convenient turbulence model for this kind of study.

    Looking at different parameters such as user-friendliness, time required, software costs and versatility, OpenFOAM proves itself to be a convenient, accurate and valid alternative to its expensive commercial counterpart. Finally, following these conclusions a user-guide method to analyze not only the single but the entire class of air intake systems for Scania internal purposes is developed and reported.

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  • 273. Cameron, C. J.
    et al.
    Larsson, Johan
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Loukil, M. S.
    Murtagh, T.
    Wennhage, Per
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics.
    Bearing strength performance of mixed thin/thick-ply, quasi-isotropic composite laminates2021In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 261, article id 113312Article in journal (Refereed)
    Abstract [en]

    The effect of using thin plies to increase the bearing strength of composite laminates has been investigated. A series of 5 laminates of theoretically identical stiffness with varying proportions of thin plies were manufactured using a single material system. Four specimens from each plate were tested for bearing strength and damage was subsequently characterized using an optical microscope. The results show that performance in terms of bearing stiffness, strength at onset of damage, and ultimate bearing stress increase proportionally with the increasing amount of thin plies within the stack. Shifting from a 100% conventional ply laminate to a 100% thin-ply laminate gave an increase of 47% in the strength at onset of damage. Placement of the thin plies within the stack was also shown to be important for strength at initial onset of damage. Microscopic examination of the failure modes for all samples showed fiber kinking, localized to the center of the hole, to be the dominant failure mode regardless of the stacking sequence.

  • 274.
    Cannon, Ianto
    et al.
    Okinawa Inst Sci & Technol Grad Univ, Complex Fluids & Flows Unit, 1919-1 Tancha, Onna Son, Okinawa 9040495, Japan..
    Izbassarov, Daulet
    Aalto Univ, Dept Mech Engn, FI-00076 Aalto, Finland..
    Tammisola, Outi
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Brandt, Luca
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Rosti, Marco E.
    Okinawa Inst Sci & Technol Grad Univ, Complex Fluids & Flows Unit, 1919-1 Tancha, Onna Son, Okinawa 9040495, Japan..
    The effect of droplet coalescence on drag in turbulent channel flows2021In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 33, no 8, article id 085112Article in journal (Refereed)
    Abstract [en]

    We study the effect of droplet coalescence on turbulent wall-bounded flows by means of direct numerical simulations. In particular, the volume-of-fluid and front-tracking methods are used to simulate turbulent channel flows containing coalescing and non-coalescing droplets, respectively. We find that coalescing droplets have a negligible effect on the drag, whereas the non-coalescing ones steadily increase drag as the volume fraction of the dispersed phase increases: indeed, at 10% volume fraction, the non-coalescing droplets show a 30% increase in drag, whereas the coalescing droplets show less than 4% increase. We explain this by looking at the wall-normal location of droplets in the channel and show that non-coalescing droplets enter the viscous sublayer, generating an interfacial shear stress, which reduces the budget for viscous stress in the channel. On the other hand, coalescing droplets migrate toward the bulk of the channel forming large aggregates, which hardly affect the viscous shear stress while damping the Reynolds shear stress. We prove this by relating the mean viscous shear stress integrated in the wall-normal direction to the centerline velocity.

  • 275.
    Canton, Jacopo
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Rinaldi, Enrico
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics. Royal Inst Technol, Linne FLOW Ctr KTH Mech, SE-10044 Stockholm, Sweden..
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Schlatter, Philipp
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Critical Point for Bifurcation Cascades and Featureless Turbulence2020In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 124, no 1, article id 014501Article in journal (Refereed)
    Abstract [en]

    In this Letter we show that a bifurcation cascade and fully sustained turbulence can share the phase space of a fluid flow system, resulting in the presence of competing stable attractors. We analyze the toroidal pipe flow, which undergoes subcritical transition to turbulence at low pipe curvatures (pipe-to-torus diameter ratio) and supercritical transition at high curvatures, as was previously documented. We unveil an additional step in the bifurcation cascade and provide evidence that, in a narrow range of intermediate curvatures, its dynamics competes with that of sustained turbulence emerging through subcritical transition mechanisms.

  • 276.
    Canton, Jacopo
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics.
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Schlatter, Philipp
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Neutral stability of the flow in a toroidal pipe2015In: Proceedings - 15th European Turbulence Conference, ETC 2015, TU Delft , 2015Conference paper (Refereed)
    Abstract [en]

    This work is concerned with the numerical investigation of the linear stability properties of the viscous, incompressible flow inside a toroidal pipe. A Hopf bifurcation is found and tracked in phase space, showing that the flow is modally unstable even at extremely low curvatures. The bifurcation and the eigenfunctions associated with it are analysed as a function of the two parameters governing the flow, i.e. the Reynolds number, Re, and the curvature, δ. For all curvatures, the critical Reynolds number is found to be about 3000. 

  • 277.
    Canton, Jacopo
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics.
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Schlatter, Philipp
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    On stability and transition in bent pipes2019In: Direct and Large-Eddy Simulation XI, Springer , 2019, p. 531-536Chapter in book (Refereed)
    Abstract [en]

    This work is concerned with the investigation of the instability and transition to turbulence of the viscous, incompressible flow inside curved pipes. For the first time, the impact of the curvature is analysed over the whole parameter space, presenting new results for both the steady flow and the instabilities encountered by this flow.

  • 278.
    Cao, Da
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics, Marcus Wallenberg Laboratory MWL.
    Modelling of the vibrational behavior of housing plates filled with fibrous material2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Silencers are used in vehicles to reduce the noise in the engine system. However,silencers themselves may produce break-out noise due to the interactionwith the exhaust gas ow and structure. In this Master thesis project, thenumerical simulation of vibrational behavior of housing plates of silencers isdeveloped.The housing plate is composed of two steel plates and a brous materiallayer. Measurement results show that the brous material has good dampingeect to decrease the vibration and radiated sound of steel plates. Steel platesare connected by spot welding. Modeling of spot welds can improve themodal assurance criterion between simulation and measurements. Interfacedamping is introduced into the simulation models to simulate the contacteect between two steel plates so that the simulated amplitude can have agood agreement with measurement result.Several numerical models of brous material are investigated. The Mikimodel is not chosen for the nal result due to the limit of range of frequencies.The rigid frame model can simulate the sound absorption but is unfeasible forthe simulation of vibration. The limp frame model can simulate the vibrationof light glass wool but cannot simulate the vibration of heavy glass wool.Finally, the Biot-Allard model which is a poro-elastic model is investigatedfor the nal result. The simulation results show good agreement with themeasurement result.

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  • 279.
    Capel Jorquera, Javier
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Rocket Jet Impinging on a Surface2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the continuous growth of the space industry and the introduction of reusable rockets, the number of rocket launches is expected to increase significantly in the following years. During rocket launching, the engine exhaust impinges on the launch structure producing a complex flow field. The rocket jet induces large thermoaerodynamic and acoustic loads on the launch structures and the rocket.

    This thesis aims to study the physics and numerical considerations behind supersonic flows exhausted from rocket engines. First, the treatment of turbulent compressible flows through the Favre-averaged equations and the SST k-ω model are studied. Next, the numerical modeling of the problem, including solver and meshing theory is presented. Then, a model of a nozzle is explained along with how the performance is assessed to finally design a M=3 two-dimensional nozzle using the method of characteristics (MOC). The two-dimensional results are validated using Ansys Fluent, and the same geometry is used for the following axisymmetrical problems, which include the study of a free and impinging jet. The free jet problem serves to study how the nozzle behaves in a two-dimensional axisymmetric problem and to validate the impinging jet results. To obtain the results, RANS-based simulations of a cold, over-expanded jet with adiabatic walls are performed. Empirical formulas were used to verify the results. Lastly, the impinging jet problem is simulated using the same inlet boundary conditions as for the free jet. The impact that the plate distance to the exit of the nozzle has on the position of the shock waves when the jet impinges on the flat surface is assessed. Finally, an optimization of the shape of a wedge to minimize the maximum turbulence kinetic energy produced during steady-state simulation is carried out. As an appendix to the work, an aeroacoustic study of the impinging jet at 4De distance is presented. The results show the direction of propagation of the acoustic waves but due to the lack of acoustic quality of the mesh, the predicted sound pressure levels do not match the expected behavior.

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  • 280.
    Caries, V.
    et al.
    Univ Lyon, Ecole Centrale de Lyon, CNRS, Univ Claude Bernard Lyon 1, INSA Lyon, LMFA, UMR5509, 69130, Ecully, France; Safran Aircraft Engine, Moissy-Cramayel, France.
    Montsarrat, Christophe
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Boudet, J.
    Univ Lyon, Ecole Centrale de Lyon, CNRS, Univ Claude Bernard Lyon 1, INSA Lyon, LMFA, UMR5509, 69130, Ecully, France.
    Lippinois, E.
    Safran Aircraft Engine, Moissy-Cramayel, France.
    Vortex lattice method for fan tip-flow modeling2023In: 15th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics 2023, ETC 2023, European Conference on Turbomachinery (ETC) , 2023Conference paper (Refereed)
    Abstract [en]

    In the present work, a low-fidelity three-dimensional approach has been developed for the prediction of the flow around shrouded rotors. This method is to be used in the initial steps of design, for a wide exploration of the design space, including disruptive geometries, at minimal cost. The present approach is based on the vortex lattice method. First, the formulation on rotating geometries is validated by comparison with experiments. The Prandtl-Glauert correction is introduced to account for mild compressibility effects. A discretized approach is proposed to model the casing and simulate the tip-leakage flow. The results are discussed for different tip-gap sizes. A periodic boundary condition is also proposed and validated. This condition, together with programming techniques, decreases the computational and memory costs of the method. On average, a computation takes approximately one second to execute in real time. Finally, the method is applied to a shrouded fan configuration and the influence of the tip-gap size is analyzed.

  • 281.
    Carlsson, M.
    et al.
    Division of Fluid Dynamics, M2, Chalmers University of Technology, Gothenburg, Sweden.
    Wallin, Stefan
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Davidson, L.
    Division of Fluid Dynamics, M2, Chalmers University of Technology, Gothenburg, Sweden.
    Peng, S. H.
    Swedish Defence Research Agency, Stockholm, Sweden.
    Arvidson, S.
    Saab Aeronautics, Linköping, Sweden.
    Seamless Interface Methods for Grey-Area Mitigation in Scale-Resolving Hybrid RANS-LES2024In: ERCOFTAC Series, Springer Science and Business Media B.V. , 2024, Vol. 31, p. 299-305Chapter in book (Other academic)
    Abstract [en]

    A new Grey-Area Mitigation (GAM) method for hybrid RANS-LES is presented.

  • 282.
    Carlsson, Ulf
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Uberti, S.
    University of Brescia, Brescia, Italy.
    Piana, E. A.
    Applied Acoustics Laboratory, University of Brescia, Brescia, Italy.
    Experimental investigation on the acoustic behaviour of a small tractor cabin2021In: "Advances in Acoustics, Noise and Vibration - 2021" Proceedings of the 27th International Congress on Sound and Vibration, ICSV 2021, Silesian University Press , 2021Conference paper (Refereed)
    Abstract [en]

    The quality and acoustic comfort of agricultural tractor cabins are nowadays highly valued by the market. For this reason, tractor manufacturers are more and more interested in improving the behaviour of their vehicles also from an acoustics point of view. A tractor cabin is an unusual environment, with a space mainly developed in the vertical direction, characterised by a relatively small volume of air and surrounded by windows, which can be considered as large reflecting surfaces. This feature causes strong standing waves that, when coupled with an acoustic source, can generate high sound pressure levels resulting in reduced comfort for the driver. This paper investigates, through measurements and simulations, the low frequency acoustic behaviour of a small tractor cabin. The technique adopted for the measurements is based on a multiple transfer function analysis. Measured frequency response functions are processed for the cabin's acoustic mode parameters. The results of the experiments are validated through a finite-element model allowing the reconstruction of the sound pressure contours inside the volume and further analyses.

  • 283.
    Carlstedt, Arvid
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Vehicle Dynamics.
    Modelling of electromechanical motors for turret and barrel control in main battle tanks2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this master thesis the dynamics of a modern main battle tank's turret traverse and gun elevation have been modelled. The models of dynamic motion have been coupled to two different types of electric motors, namely a direct-current motor and an induction motor. These have been modelled in MATLAB and SIMULINK together with the mechanical systems in the turret traverse and gun elevation. The goal of this project was to develop non-ideal models of the combined mechanical and electrical systems, but the main focus has been the dynamics of the electric motors.

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  • 284.
    Carlstedt, David
    et al.
    Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg, SE-41296, Sweden.
    Johannisson, Wilhelm
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics.
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics.
    Linde, Peter
    Asp, Leif E.
    Conceptual design framework for laminated structural battery composites2020In: ECCM 2018 - 18th European Conference on Composite Materials, Applied Mechanics Laboratory , 2020Conference paper (Refereed)
    Abstract [en]

    The structural battery composite is a class of composite materials with ability to provide mechanical integrity in a structural system while simultaneously store electrical energy (i.e. work as a battery). In this paper a framework to estimate the mechanical and electrical performance of laminated structural battery composites is proposed. The mechanical performance of the battery composite laminate is assessed by estimating the in-plane elastic properties of the laminate using Classical Laminate Theory. The electrical performance is assessed estimating the specific capacity and energy density of the component. The developed framework is applied on an A4 sized structural battery composite demonstrator, as part of the Clean Sky 2 project SORCERER [1] to demonstrate the capabilities of the framework. The design process for the demonstrator is presented and mechanical and electrical performance metrics are estimated for three laminate configurations, one promoting structural performance, one promoting electrical performance and one intermediate. As the material provides both load carrying and electrical energy storage capabilities, the laminate configuration can be alternated to provide suitable performance based on the purpose of the component. 

  • 285.
    Casanueva, Carlos
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Rail Vehicles.
    Alonso, Asier
    CAF I+D, Spain.
    Bernsteiner, Christof
    VIRTUAL VEHICLE Research Center, Austria.
    Czerwinka, Thomas
    Siemens AG, Austria.
    Gabriel, Daniel
    Stadler Rail Valencia, Spain.
    Gonzalez-Larrache, Xabier
    Siemens AG, Austria.
    Marte, Christof
    VIRTUAL VEHICLE Research Center, Austria.
    Muñoz, Jesús
    Stadler Rail Valencia, Spain.
    Orbegozo, Ane
    CAF I+D, Spain.
    Paar, Roland
    Siemens AG, Austria.
    Energy Prediction Benchmark for Universal CostModel Calculations2018Conference paper (Refereed)
    Abstract [en]

    Within the EU project Roll2Rail a Universal Cost Model (UCM) is being developed that accounts for different costs in the railway system affected by the design of the running gear. The objective of the methodology is not to calculate the global LCC of the entire vehicle (with all its components) but to boost the introduction of new technologies in the bogie by calculating the savings or incremental costs on the LCC that could be obtained between technological alternatives. The UCM will allow a more objective comparison of different bogie concepts, for instance in purchasing processes, and thus it includes a trustworthiness analysis that evaluates how accurate the calculations in the UCM are for a given study.

    When looking at the total life-cycle cost of a railway vehicle, energy consumption accounts for about 5% of the total expenditure. Within this UCM, a methodology has been proposed that allows the calculation of the energy consumption related to the bogie-technology of any railway vehicle. In order to ensure that all the calculation tools developed by the different partners are adequate, a benchmark simulation has been carried out. The benchmark studies a high-speed vehicle composed of two powered units and four non-powered ones, including six conventional bogies and three Jacobs bogies with both mechanical and ED brakes. In order to validate each simulation tool the share of energy consumed is then compared in different concepts, including in the fields of rolling resistance, curve resistance, unstable running resistance, gradient resistance, aerodynamic and turbulent resistance, inertia resistance and energy use of auxiliary elements. It should be stressed that the comparison and validation focuses on bogie-influenced energy consumption.

    In this paper, the overall UCM methodology is described, with special focus on the energy calculation methodology. The benchmark case is then presented and the energy calculation of all the partners is compared. A discussion on the calibration of the different partners' calculation tools is carried out, including a follow-updiscussion on the relative importance of the different energy consumption concepts in the final energy expenditure. Finally, the trustworthiness analysis is recalibrated according to these results. Closing remarks aregiven addressing the influence of these costs on the UCM.

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  • 286.
    Casanueva, Carlos
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Rail Vehicles.
    Dirks, Babette
    Trafikverket.
    Tohmmy, Bustad
    Trafikverket.
    Rail Vehicle Dynamics Simulation-based decision support for novel block brake material implementation in Sweden2019In: THE 26TH IAVSD INTERNATIONAL SYMPOSIUM ON DYNAMICS OF VEHICLES ON ROADS AND TRACKS, 12-16 August 2019, Gothenburg, Sweden, 2019Conference paper (Other academic)
    Abstract [en]

    . The application of TSI Noise in Sweden needs decision support that can objectively state system-wide benefits and disadvantages, as there are issues with the introduction of novel block brakes: reduced braking performance and increased equivalent conicity. The Roll2Rail Universal Cost Model (UCM) is used to analyse Life Cycle Cost (LCC), as it was also conceived so that it could be used within the decision making processes of infrastructure managers. The simulated characteristics are mainly track Rolling Contact Fatigue (RCF) due to the worsened dynamic train-track interaction.

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  • 287.
    Casanueva, Carlos
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Rail Vehicles.
    Krishna, Visakh V
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Stichel, Sebastian
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Rail Vehicles.
    System-wide impact of vehicle innovations: Evaluating track-friendliness during vehicle design2021In: Proceedings of the Resource Efficient Vehicles Conference - 2021 (rev2021), 2021Conference paper (Refereed)
    Abstract [en]

    The cost of maintenance of railway tracks due to vehicle passage is a major limiting factor to the competitiveness of railway sector in EU. For instance, in Sweden in 2017only, 2800million SEK was spent on track maintenance and reinvestment due to wear and tear caused by traffic. Considering this, there is a major incentive to operate track-friendly vehicles that also facilitate economically feasible maintenance strategies. In this context, the NEXTGEAR project aims to incorporate a track-friendliness module in the ‘Universal Cost Model 2.0’ that can estimate operating costs for a given set of operational parameters such as vehicle suspension design, energy usage, track geometry, etc. Such a tool could be useful in estimating the costs for a train operator for a given route and application. However, estimation of costs due to track damage is a complex cross-disciplinary task encompassing varying domains such as vehicle dynamics, tribology, economics, maintenance policy etc so that actual damage in the infrastructure can be linked to maintenance actions and thus costs. Currently there are two major diametrical approaches such as the ‘Bottom-up’ Engineering approach that seeks to create accurate engineeringmodels of vehicle, track, etc. Then there is the ‘Top-down’ Econometric approach that seeks to create statistical models linking the operating variables with historically recorded cost data. Also, track damage itself manifests in various forms such as wear RCF and settlement and it is extremely useful to understand the distribution of costs amongst them. Nowadays a Hybrid approach isbeingdeveloped that can bridge the limitations of the other two methods. Eventually all these models seek to calculate differential operating costs due to the introduction of vehicle innovations during the design stage, hence contributing to the overall economic feasibility of the railway system

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  • 288.
    Casanueva, Carlos
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics.
    Matz, Christian
    KTH.
    Abramović, Borna
    University of Zagreb, Zagreb, Croatia.
    Šipuš, Denis
    University of Zagreb, Zagreb, Croatia.
    Calonge, David
    EURNEX, Southampton, UK.
    Svensson, Kristina
    EURNEX, Southampton, UK.
    Current Gaps and Mismatches Between Rail Higher Education Provision and Industry Expectations2024In: Sustainable Rail Transport 5: Skills Development, Education and Leadership in the Railway Sector, Springer Nature , 2024, Vol. Part F2364, p. 29-53Chapter in book (Other academic)
    Abstract [en]

    The expectations of railway companies are not always aligned with the skills and abilities that university graduates bring when finishing their studies. This work firstly analyses the higher education study paths related to railways and their flexibility; then surveys the expectations of a set of European railway stakeholders in order to get the most looked after skills and abilities; next it analyses sectors other than the railways looking for academic best practices; and in the end it matches the most sought after skills within the Rail Careers Matrix for determining the relative importance of these skills in the operational, tactical, and strategic levels. The final result is a visual representation of the skills gaps and mismatches that European railway companies need to cover in the context of the actual Higher Education in the European landscape.

  • 289. Cascone, C.
    et al.
    Murphy, K. R.
    Markensten, H.
    Kern, J. S.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Schleich, C.
    Keucken, A.
    Köhler, S. J.
    AbspectroscoPY, a Python toolbox for absorbance-based sensor data in water quality monitoring2022In: Environmental Science: Water Research & Technology, ISSN 2053-1400, E-ISSN 2053-1419, Vol. 8, no 4, p. 836-848Article in journal (Refereed)
    Abstract [en]

    The long-term trend of increasing natural organic matter (NOM) in boreal and north European surface waters represents an economic and environmental challenge for drinking water treatment plants (DWTPs). High-frequency measurements from absorbance-based online spectrophotometers are often used in modern DWTPs to measure the chromophoric fraction of dissolved organic matter (CDOM) over time. These data contain valuable information that can be used to optimise NOM removal at various stages of treatment and/or diagnose the causes of underperformance at the DWTP. However, automated monitoring systems generate large datasets that need careful preprocessing, followed by variable selection and signal processing before interpretation. In this work we introduce AbspectroscoPY (“Absorbance spectroscopic analysis in Python”), a Python toolbox for processing time-series datasets collected by in situ spectrophotometers. The toolbox addresses some of the main challenges in data preprocessing by handling duplicates, systematic time shifts, baseline corrections and outliers. It contains automated functions to compute a range of spectral metrics for the time-series data, including absorbance ratios, exponential fits, slope ratios and spectral slope curves. To demonstrate its utility, AbspectroscoPY was applied to 15-month datasets from three online spectrophotometers in a drinking water treatment plant. Despite only small variations in surface water quality over the time period, variability in the spectrophotometric profiles of treated water could be identified, quantified and related to lake turnover or operational changes in the DWTP. This toolbox represents a step toward automated early warning systems for detecting and responding to potential threats to treatment performance caused by rapid changes in incoming water quality. 

  • 290.
    Castellani, Francesco
    et al.
    Univ Perugia, Dept Engn, Via G Durand 93, I-06125 Perugia, Italy..
    Eltayesh, Abdelgalil
    Benha Univ, Benha Fac Engn, Mech Engn Dept, Banha 13512, Egypt..
    Becchetti, Matteo
    Univ Perugia, Dept Engn, Via G Durand 93, I-06125 Perugia, Italy..
    Segalini, Antonio
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Aerodynamic Analysis of a Wind-Turbine Rotor Affected by Pitch Unbalance2021In: Energies, E-ISSN 1996-1073, Vol. 14, no 3, article id 745Article in journal (Refereed)
    Abstract [en]

    The aerodynamics of a rotor with pitch imbalance has been investigated experimentally and numerically in the present work. The comparison of mean velocity and turbulence intensity in the balanced and unbalanced cases indicated that a pitch imbalance modifies both the mean velocity and the turbulent activity; the latter is weakly increased by the imbalance. Spectral analysis indicated that the dynamics of the wake is also affected by the pitch imbalance since the tip vortices loose strength and disorganise more quickly than in the balanced case. The pitch imbalance has, however, a detrimental effect on the power coefficient and it affects the thrust coefficient as well. Only the blade affected by the imbalance shows significant modifications of the applied load, while the other blades operate with the same loading conditions.

  • 291.
    Castillo Aguilar, Juan Jesús
    et al.
    Department of Mechanical Engineering, University of Málaga, Spain.
    Postigo Pozo, Sergio
    Department of Mechanical Engineering, University of Málaga, Spain.
    Ruiz Mora, Isabel
    Depatment of Advertising and Audiovisual Communication, University of Málaga, Spain.
    Casanueva, Carlos
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Väg- och spårfordon samt konceptuell fordonsdesign.
    Abramovic, Borna
    University of Zagreb.
    Marin, Marinov
    Aston University.
    Aplicación de la metodología basada en Design Thinking para el aprendizaje de conceptos técnicos ferroviarios2022In: XV Congreso Iberoamericano de Ingeniería Mecánica, UNED - Universidad Nacional de Educacion a Distancia , 2022Conference paper (Other academic)
    Abstract [en]

    Professors and researchers from the areas of Mechanical Engineering and Audiovisual Communication of the University of Malaga participate in a European Erasmus+ project called ASTONRail. Among the activities developed during the execution of this project, an intensive course on different topics within the railway field was designed. Students from different universities attended classes on railway safety, infrastructure, operation, administration and management, rolling stock and technology. The session on rolling stock was given by lecturers from the University of Malaga and KTH Royal Institute of Technology. For this session, the methodologies used were Design Thinking, collaborative learning and flipped classroom. This paper will describe the project within which the activity was planned and its motivation. It will also present the development of the activity and the evaluation of the results achieved

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  • 292.
    Ceccato, Chiara
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Brandberg, August
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Kulachenko, Artem
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Barbier, Christophe
    BillerudKorsnäs, Grums, Värmland County, Sweden.
    Micro-mechanical modeling of the paper compaction process2021In: Acta Mechanica, ISSN 0001-5970, E-ISSN 1619-6937, Vol. 232, no 9, p. 3701-3722Article in journal (Refereed)
    Abstract [en]

    Double-roll compaction is a process to create extensible paper and paperboard suitable for replacing plastic in 3D forming applications. Understanding the macro- and micro-mechanisms governing the compaction process allows increasing the stretch potential while maintaining sufficient strength and bending stiffness. In this work, we approach the compaction process of paperboard with micro-mechanical methods featuring the unprecedented level of details otherwise inaccessible with currently available experimental tools. The loading scheme is based on experiments and continuum level simulations. The different levels of compaction and their continuous impact on the fibers’ geometry, void closures, and irreversible deformation of the fibers are thoroughly characterized. We find that the structural changes are concentrated in the fibers oriented within 30 degrees of the direction of compaction. The deformation accumulates primarily in the wall of the fibers in the form of irreversible strains. The spring-back effect beyond the compaction is negligible. For the first time, the role of normal and frictional fiber-to-fiber interactions in the compaction process is investigated and quantified. The frictional interaction between the fibers has a surprisingly low impact on the outcome of the compaction process, and the normal interaction between the fibers has a dominant response. The consequence of this finding is potentially limited impact of the surface modifications targeting the friction.

  • 293.
    Ceccato, Chiara
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Kulachenko, Artem
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Barbier, C.
    BillerudKorsnäs, Grums, Värmland County, Sweden.
    Investigation of rolling contact between metal and rubber-covered cylinders governing the paper compaction process2019In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 163, article id 105156Article in journal (Refereed)
    Abstract [en]

    With the goal of partial or complete replacement of plastic components with paper-based products, 3D paper structures have seen a growing interest in industrial applications: from packaging to more complex daily life objects. However, the extensibility of paper has become a key issue within this context and is the main factor determining the formability of these products and determining the depth of the achievable shapes. The most effective way to increase paper's stretch potential is by subjecting the moist paper web to a compaction process, which can be achieved through an extensible unit that is located in the drying section of a paper machine, where the network experiences in-plane compression in the machine direction (MD), under out-of-plane lateral constraints. The objective of this work is to clarify the mechanisms governing the compression process and to evaluate the influence of various parameters on the final material properties to optimize the industrial production of extensible paper. The system operation has been simulated realistically and shows that paper experiences a compressive state passing through the nip, with plastic strains in MD direction being of the same order of the applied speed difference, which was expected experimentally in optimal conditions of compaction. Starting from an initial reference case, a sensitivity study has been performed to identify and address the following factors that may affect the compression state: (a) friction coefficients; (b) indentation level; (c) speed difference; and (d) rubber properties. The analysis of the numerical results gives an insight into the mechanisms governing the compaction operations and allows a better comprehension of the features controlling the process outcome.

  • 294.
    Cederqvist, Hugo
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Väg- och spårfordon samt konceptuell fordonsdesign.
    Development of validation tool for antenna positioners on vehicles in motion2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Artificial satellites play a vital role throughout the world today. They providea broad range of services ranging from navigation to communication and reconnaissance. As antenna technology is evolving and ground based antennas are getting smaller and smaller, the demand for on-the-move solutions is growing.These antennas can be used whilst mounted on for example, a moving vehicle,where the mechanical performance of the antenna must be sufficient for thecurrent conditions. During this project, a computer based tool that can helpengineers when iterating and optimizing a two-axis gimbal type antenna designwas created. The tool uses simulated and recorded data from road vehicles andboats to calculate the required torque on the two axes necessary to sustain communication with a geostationary satellite. When completed, the tool was easy to use and configure whilst not requiring much computational power.

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  • 295.
    Cenni, Francesco
    et al.
    Univ Jyvaskyla, Fac Sport & Hlth Sci, Jyvaskyla, Finland.;Univ Jyvaskyla, Fac Sport & Hlth Sci, Rautpohjankatu 8, Jyvaskyla 40700, Finland..
    Alexander, Nathalie
    Childrens Hosp Eastern Switzerland, Lab Mot Anal, St Gallen, Switzerland..
    Sukanen, Maria
    Univ Jyvaskyla, Fac Sport & Hlth Sci, Jyvaskyla, Finland..
    Mustafaoglu, Afet
    Univ Jyvaskyla, Fac Sport & Hlth Sci, Jyvaskyla, Finland..
    Wang, Zhongzheng
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH MoveAbility.
    Wang, Ruoli
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH MoveAbility.
    Finni, Taija
    Univ Jyvaskyla, Fac Sport & Hlth Sci, Jyvaskyla, Finland..
    ISB clinical biomechanics award winner 2023: Medial gastrocnemius muscle and Achilles tendon interplay during gait in cerebral palsy2024In: Clinical Biomechanics, ISSN 0268-0033, E-ISSN 1879-1271, Vol. 111, article id 106158Article in journal (Refereed)
    Abstract [en]

    Background: The interplay between the medial gastrocnemius muscle and the Achilles tendon is crucial for efficient walking. In cerebral palsy, muscle and tendon remodelling alters the role of contractile and elastic components. The aim was to investigate the length changes of medial gastrocnemius belly and fascicles, and Achilles tendon to understand their interplay to gait propulsion in individuals with cerebral palsy.Methods: Twelve young individuals with cerebral palsy and 12 typically developed peers were assessed during multiple gait cycles using 3D gait analysis combined with a portable ultrasound device. By mapping ultrasound image locations into the shank reference frame, the medial gastrocnemius belly, fascicle, and Achilles tendon lengths were estimated throughout the gait cycle. Participants with cerebral palsy were classified into equinus and non-equinus groups based on their sagittal ankle kinematics.Findings: In typically developed participants, the Achilles tendon undertook most of the muscle-tendon unit lengthening during stance, whereas in individuals with cerebral palsy, this lengthening was shared between the medial gastrocnemius belly and Achilles tendon, which was more evident in the equinus group. The lengthening behaviour of the medial gastrocnemius fascicles resembled that of the Achilles tendon in cerebral palsy. Interpretation: The findings revealed similar length changes of the medial gastrocnemius fascicles and Achilles tendon, highlighting the enhanced role of the muscle in absorbing energy during stance in cerebral palsy. These results, together with the current knowledge of increased intramuscular stiffness, suggest the exploitation of intramuscular passive forces for such energy absorption.

  • 296. Chan, C. , I
    et al.
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Schlatter, Philipp
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Chin, R. C.
    Univ Adelaide, Sch Mech Engn, Adelaide, SA 5005, Australia..
    Large-scale and small-scale contribution to the skin friction reduction in a modified turbulent boundary layer by a large-eddy break-up device2022In: Physical Review Fluids, E-ISSN 2469-990X, Vol. 7, no 3, article id 034601Article in journal (Refereed)
    Abstract [en]

    The role of streamwise length scales (lambda x) in turbulent skin friction generation is investigated using a direct numerical simulation data set of an incompressible zero pressure gradient turbulent boundary layer and the spectral analysis based on the FukagataL73 (2002)]. The total skin friction generation associated with motions scaled with local boundary layer thickness delta of lambda x 3 delta and lambda x 3 delta) contribute to a significant portion of turbulent skin friction. However, it is found that the large-scale ejection and sweep events with streamwise length scales at lambda x 3 delta are equally important. The turbulent skin friction reduction associated with the modification of largeand small-scale quadrant events is studied, using well-resolved simulation data sets of a large-eddy break-up (LEBU) device in a turbulent boundary layer. The results reveal that LEBUs modify both the large- and small-scale ejection and sweep events, yielding a substantial turbulent skin friction reduction.

  • 297.
    Chan, I. C.
    et al.
    Univ Adelaide, Sch Mech Engn, Adelaide, SA 5005, Australia..
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Schlatter, Philipp
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Chin, R. C.
    Univ Adelaide, Sch Mech Engn, Adelaide, SA 5005, Australia..
    The skin-friction coefficient of a turbulent boundary layer modified by a large-eddy break-up device2021In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 33, no 3, article id 035153Article in journal (Refereed)
    Abstract [en]

    A computational study based on well-resolved large-eddy simulations is performed to study the skin friction modification by a large-eddy breakup device (LEBU) in a zero-pressure-gradient turbulent boundary layer. The LEBU was modeled using an immersed boundary method. It is observed that the presence of the device leads to the generation of wake vortices, which propagate downstream from the LEBU and toward the wall. A skin friction decomposition procedure is utilized to study different physical mechanisms of the observed skin friction reduction. From the skin friction decomposition, it is found that the skin friction reduction can be characterized by three universal regions of different changes for the skin friction contributions. The first region is predominantly associated with the formation of the wake vortices and the reduction of Reynolds shear stress. In the second region, the mean streamwise velocity fields show that a region of velocity deficit formed downstream of the LEBU propagates toward the wall and leads to turbulence reduction due to wake wall interactions, which also induces a local maximum skin friction reduction. In the third region, the dissipation of wake vortices leads to the regeneration of Reynolds shear stress. A quadrant analysis of the Reynolds shear stress contribution reveals that the LEBU increases the Q2 and Q4 contributions and attenuates the Q1 and Q3 contributions in the first region, followed by an onset of Reynolds shear stress further downstream.

  • 298.
    Chaparian, Emad
    et al.
    KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Izbassarov, Daulet
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    De Vita, Francesco
    KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics. Royal Inst Technol KTH, Mech Dept, SERC, Stockholm, Sweden..
    Brandt, Luca
    KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics. Royal Inst Technol KTH, Mech Dept, SERC, Stockholm, Sweden..
    Tammisola, Outi
    KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Yield-stress fluids in porous media: a comparison of viscoplastic and elastoviscoplastic flows2020In: Meccanica (Milano. Print), ISSN 0025-6455, E-ISSN 1572-9648, Vol. 55, no 2, p. 331-342Article in journal (Refereed)
    Abstract [en]

    A numerical and theoretical study of yield-stress fluid flows in two types of model porous media is presented. We focus on viscoplastic and elastoviscoplastic flows to reveal some differences and similarities between these two classes of flows. Small elastic effects increase the pressure drop and also the size of unyielded regions in the flow which is the consequence of different stress solutions compare to viscoplastic flows. Yet, the velocity fields in the viscoplastic and elastoviscoplastic flows are comparable for small elastic effects. By increasing the yield stress, the difference in the pressure drops between the two classes of flows becomes smaller and smaller for both considered geometries. When the elastic effects increase, the elastoviscoplastic flow becomes time-dependent and some oscillations in the flow can be observed. Focusing on the regime of very large yield stress effects in the viscoplastic flow, we address in detail the interesting limit of 'flow/no flow': yield-stress fluids can resist small imposed pressure gradients and remain quiescent. The critical pressure gradient which should be exceeded to guarantee a continuous flow in the porous media will be reported. Finally, we propose a theoretical framework for studying the 'yield limit' in the porous media.

  • 299.
    Chaparian, Emad
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Niazi Ardekani, Mehdi
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Brandt, Luca
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Tammisola, Outi
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Particle migration in channel flow of an elastoviscoplastic fluid2020In: Journal of Non-Newtonian Fluid Mechanics, ISSN 0377-0257, E-ISSN 1873-2631, Vol. 284, article id 104376Article in journal (Refereed)
    Abstract [en]

    We study the dynamics of a neutrally buoyant rigid sphere carried by an elastoviscoplastic fluid in a pressure-driven channel flow numerically. The yielding to flow is marked by the yield stress which splits the flow into two main regions: the core unyielded region and two sheared yielded regions close to the walls. The particles which are initially in the plug region are observed to translate with the same velocity as the plug without any rotation/migration. Keeping the Reynolds number fixed, we study the effect of elasticity (Weissenberg number) and plasticity (Bingham number) of the fluid on the particle migration inside the sheared regions. In the viscoelastic limit, in the range of studied parameters (low elasticity), inertia is dominant and the particle finds its equilibrium position between the centreline and the wall. The same happens in the viscoplastic limit, yet the yield surface plays the role of centreline. However, the combination of elasticity and plasticity of the suspending fluid (elastoviscoplasticity) trigger particle-focusing: in the elastoviscoplastic flow, for a certain range of Weissenberg numbers (≈0.5), isolated particles migrate all the way to the centreline by entering into the core plug region. This behaviour suggests a particle-focusing process for inertial regimes which was not previously found in a viscoelastic or viscoplastic carrying fluid. 

  • 300.
    Chaparian, Emad
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Tammisola, Outi
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    An adaptive finite element method for elastoviscoplastic fluid flows2019In: Journal of Non-Newtonian Fluid Mechanics, ISSN 0377-0257, E-ISSN 1873-2631, Vol. 271, p. 104148-Article in journal (Refereed)
    Abstract [en]

    Elastoviscoplastic fluids are a class of yield-stress fluids that behave like neoHookean (or viscoelastic) solids when the imposed stress is less than the yield stress whereas after yielding, their behaviour is described by a viscoplastic fluid with an additional elastic history. This exceptional behaviour has been recently observed by many yield stress fluids in rheometric tests such as waxy crude oil, Carbopol gel, etc. Moreover, interesting phenomena have been evidenced experimentally such as the presence of a negative wake and a loss of fore-aft symmetry about a settling particle which are predominantly related to the elastic behaviour of yield-stress fluids (i.e., coupling of elasticity and plasticity). Here, we present a numerical scheme based on the so-called augmented Lagrangian method for numerical simulation of elastoviscoplastic fluid flows. The method is benchmarked by two rheometric flows: Poiseuille and circular Couette flows for which analytical solutions are derived. Moreover, anisotropic adaptive mesh procedure (which was previously introduced for viscoplastic fluid flows by Saramito and Roquet, Comput. Meth. Appl. Mech. Eng., vol. 190, 2001, pp. 5391-5412) is coupled to obtain a fine resolution of the yield surfaces. Finally, the presented method is applied to study more complex flows: elastoviscoplastic fluid flow in a wavy channel.

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