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  • 1.
    Bouchouireb, Hamza
    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.
    Advancing the life cycle energy optimisation methodology2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Life Cycle Energy Optimisation (LCEO) methodology aims at finding a design solution that uses a minimum amount of cumulative energy demand over the different phases of the vehicle's life cycle, while complying with a set of functional constraints. This effectively balances trade-offs, and therewith avoids sub-optimal shifting between the energy demand for the cradle-to-production of materials, operation of the vehicle, and end-of-life phases. This work further develops the LCEO methodology and expands its scope through three main methodological contributions which, for illustrative purposes, were applied to a vehicle sub-system design case study.

    An End-Of-Life (EOL) model, based on the substitution with a correction factor method, is included to estimate the energy credits and burdens that originate from EOL vehicle processing. Multiple recycling scenarios with different levels of assumed induced recyclate material property degradation were built, and their impact on the LCEO methodology's outcomes was compared to that of scenarios based on landfilling and incineration with energy recovery. The results show that the inclusion of EOL modelling in the LCEO methodology can alter material use patterns and significantly effect the life cycle energy of the optimal designs.

    Furthermore, the previous model is expanded to enable holistic vehicle product system design with the LCEO methodology. The constrained optimisation of a vehicle sub-system, and the design of a subset of the processes which are applied to it during its life cycle, are simultaneously optimised for a minimal product system life cycle energy. In particular, a subset of the EOL processes' parameters are considered as continuous design variables with associated barrier functions that control their feasibility. The results show that the LCEO methodology can be used to find an optimal design along with its associated ideal synthetic EOL scenario. Moreover, the ability of the method to identify the underlying mechanisms enabling the optimal solution's trade-offs is further demonstrated.

    Finally, the functional scope of the methodology is expanded through the inclusion of shape-related variables and aerodynamic drag estimations. Here, vehicle curvature is taken into account in the LCEO methodology through its impact on the aerodynamic drag and therewith its related operational energy demand. In turn, aerodynamic drag is considered through the estimation of the drag coefficient of a vehicle body shape using computational fluid dynamics simulations. The aforementioned coefficient is further used to estimate the energy required by the vehicle to overcome aerodynamic drag. The results demonstrate the ability of the LCEO methodology to capitalise on the underlying functional alignment of the structural and aerodynamic requirements, as well as the need for an allocation strategy for the aerodynamic drag energy within the context of vehicle sub-system redesign.

    Overall, these methodological developments contributed to the exploration of the ability of the LCEO methodology to handle life cycle and functional trade-offs to achieve life cycle energy optimal vehicle designs.

  • 2.
    De Vita, Francesco
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Lagrée, P. -Y
    Sorbonne Université, CNRS, Institut Jean le Rond d'Alembert, Paris, 75005, France.
    Chibbaro, S.
    Sorbonne Université, CNRS, Institut Jean le Rond d'Alembert, Paris, 75005, France.
    Popinet, S.
    Sorbonne Université, CNRS, Institut Jean le Rond d'Alembert, Paris, 75005, France.
    Beyond Shallow Water: Appraisal of a numerical approach to hydraulic jumps based upon the Boundary Layer theory2020In: European journal of mechanics. B, Fluids, ISSN 0997-7546, E-ISSN 1873-7390, Vol. 79, p. 233-246Article in journal (Refereed)
    Abstract [en]

    We study the flow of a thin layer of fluid over a flat surface. Commonly, the 1-D Shallow-water or Saint-Venant set of equations are used to compute the solution of such flows. These simplified equations may be obtained through the integration of the Navier–Stokes equations over the depth of the fluid, but their solution requires the introduction of constitutive relations based on strict hypothesis on the flow régime. Here, we present an approach based on a kind of boundary layer system with hydrostatic pressure. This relaxes the need for closure relations which are instead obtained as solutions of the computation. It is then demonstrated that the corresponding closures are very dependent on the type of flow considered, for example laminar viscous slumps or hydraulic jumps. This has important practical consequences as far as the applicability of standard closures is concerned.

  • 3.
    Lacis, Ugis
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Sudhakar, Y.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. School of Mechanical Sciences, Indian Institute of Technology Goa, Ponda, 403401, India.
    Pasche, Simon
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Bagheri, Shervin
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Transfer of mass and momentum at rough and porous surfaces2020In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 884, article id A21Article in journal (Refereed)
    Abstract [en]

    The surface texture of materials plays a critical role in wettability, turbulence and transport phenomena. In order to design surfaces for these applications, it is desirable to characterise non-smooth and porous materials by their ability to exchange mass and momentum with flowing fluids. While the underlying physics of the tangential (slip) velocity at a fluid-solid interface is well understood, the importance and treatment of normal (transpiration) velocity and normal stress is unclear. We show that, when the slip velocity varies at an interface above the texture, a non-zero transpiration velocity arises from mass conservation. The ability of a given surface texture to accommodate a normal velocity of this kind is quantified by a transpiration length. We further demonstrate that normal momentum transfer gives rise to a pressure jump. For a porous material, the pressure jump can be characterised by so-called resistance coefficients. By solving five Stokes problems, the introduced measures of slip, transpiration and resistance can be determined for any anisotropic non-smooth surface consisting of regularly repeating geometric patterns. The proposed conditions are a subset of the effective boundary conditions derived from formal multi-scale expansion. We validate and demonstrate the physical significance of the effective conditions on two canonical problems - a lid-driven cavity and a turbulent channel flow, both with non-smooth bottom surfaces.

  • 4.
    Marchioli, C.
    et al.
    Univ Udine, Dept Engn & Architecture, I-33100 Udine, Italy.;CISM, Dept Fluid Mech, I-33100 Udine, Italy..
    Bhatia, H.
    Univ Udine, Dept Engn & Architecture, I-33100 Udine, Italy..
    Sardina, G.
    Chalmers Univ Technol, Dept Mech & Maritime Sci, Div Fluid Dynam, S-41258 Gothenburg, Sweden..
    Brandt, Luca
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Soldati, A.
    Univ Udine, Dept Engn & Architecture, I-33100 Udine, Italy.;TU Wien, Inst Fluid Mech & Heat Transfer, A-1040 Vienna, Austria..
    Role of large-scale advection and small-scale turbulence on vertical migration of gyrotactic swimmers2019In: Physical Review Fluids, E-ISSN 2469-990X, Vol. 4, no 12, article id 124304Article in journal (Refereed)
    Abstract [en]

    In this work, we use direct-numerical-simulation-based Eulerian-Lagrangian simulations to investigate the dynamics of small gyrotactic swimmers in free-surface turbulence. We consider open-channel flow turbulence in which bottom-heavy swimmers are dispersed. Swimmers are characterized by different vertical stability, so that some realign to swim upward with a characteristic time smaller than the Kolmogorov timescale, while others possess a reorientation time longer than the Kolmogorov timescale. We cover one order of magnitude in the flow Reynolds number and two orders of magnitude in the stability number, which is a measure of bottom heaviness. We observe that large-scale advection dominates vertical motion when the stability number, scaled on the local Kolmogorov timescale of the flow, is larger than unity: This condition is associated to enhanced migration toward the surface, particularly at low Reynolds number, when swimmers can rise through surface renewal motions that originate directly from the bottom-boundary turbulent bursts. Conversely, small-scale effects become more important when the Kolmogorov-based stability number is below unity: Under this condition, migration toward the surface is hindered, particularly at high Reynolds, when bottom-boundary bursts are less effective in bringing bulk fluid to the surface. In an effort to provide scaling arguments to improve predictions of models for motile microorganisms in turbulent water bodies, we demonstrate that a Kolmogorov-based stability number around unity represents a threshold beyond which swimmer capability to reach the free surface and form clusters saturates.

  • 5.
    Marin, Gustav
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics. RISE Innventia.
    Nygårds, Mikael
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Östlund, Sören
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Stiffness and strength properties of five paperboards and their moisture dependency2019In: Proceedings of the 2019 International Paper Physics Conference / [ed] Doug Coffin, Tappi , 2019Conference paper (Refereed)
    Abstract [en]

    Five folding box boards made on the same paperboard machine have been analyzed. The paperboards were from the same product series but had different grammage (235, 255, 270, 315, 340 g/m2) and different bending stiffness. The paperboards are normally used to make packages, and since the bending stiffness and grammage varies the packages performance will be different. Finite element simulations can be used to predict these differences. However, the stiffness and strength properties then need to be known. For efficient determination of the three-dimensional properties in MD, CD and ZD, it is proposed that the whole paperboard should be characterized with the following tests: in-plane tension, ZD tension, shear strength profiles and two-point bending. The stiffness and strength properties have with the proposed setups been determined at different relative humidity (20, 50, 70 and 90 % RH), and the mechanical properties have been evaluated as function of moisture ratio.

    The results showed a linear relation between mechanical properties and moisture ratio for each paperboard. The data was then normalized with data for the standard climate (50 % RH) and investigated as a function of moisture ratio. The results indicated that the normalized mechanical properties for all paperboards coincided along one single line and could therefore be expressed as a linear function of moisture ratio and two constants.

    Consequently, the study indicates that it is possible to obtain the mechanical properties of a paperboard, by knowing the structural properties for the preferred level of RH and the mechanical property for the standard climate (50 % RH and 23 °C).

  • 6.
    Nagib, H. M.
    et al.
    IIT, Dept MMAE, Chicago, IL 60616 USA..
    Vidal, A.
    IIT, Dept MMAE, Chicago, IL 60616 USA..
    Vinuesa, Ricardo
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Vorticity fluxes: A tool for three-dimensional and secondary flows in turbulent shear flows2019In: Journal of Fluids and Structures, ISSN 0889-9746, E-ISSN 1095-8622, Vol. 89, p. 39-48Article in journal (Refereed)
    Abstract [en]

    In this work we extend the vorticity-flux approach, proposed by Brown and Roshko (2012) for the analysis of turbulent shear layers and wakes, to the study of secondary flows of Prandtl's second kind. To this end, we assess direct numerical simulations (DNSs) of turbulent flow through sinusoidal channels (Vidal et al., 2018a) at bulk Reynolds numbers Re h = 2500 and 5000, and with various wall wave parameters, leading to a range of secondary flow intensities. We find that the fluctuating vorticity-flux difference (w'omega(y)') over bar (+) - (v'omega(z)') over bar (+) is closely connected to the in-plane cross-flow, in particular the large negative values present around the wall peak, which enhance the transport of near-wall momentum towards the channel core. The tilting of sweep events at the wall valley is also connected to the secondary flow magnitude, and is associated with positive values of the fluctuating vorticity-flux difference. Furthermore, conditionally averaged fields show that, unlike what is observed in channels with flat walls, the behavior in the vorticity-flux field at the peak is mostly due to Q1 and Q4 events, which essentially tilt momentum towards the peak.

  • 7.
    Rezaeiravesh, Saleh
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Vinuesa, Ricardo
    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.
    Schlatter, Philipp
    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.
    A statistics toolbox for turbulent pipe flow in Nek50002019Report (Other academic)
  • 8.
    Straub, Steffen
    et al.
    Karlsruhe Inst Technol, Inst Fluid Mech, D-76131 Karlsruhe, Germany..
    Forooghi, Pourya
    Karlsruhe Inst Technol, Inst Fluid Mech, D-76131 Karlsruhe, Germany..
    Marocco, Luca
    Politecn Milan, Dipartimento Energia, I-20156 Milan, Italy..
    Wetzel, Thomas
    Karlsruhe Inst Technol, Inst Thermal Proc Engn, D-76131 Karlsruhe, Germany..
    Vinuesa, Ricardo
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Stability, Transition and Control.
    Schlatter, Philipp
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Stability, Transition and Control.
    Frohnapfel, Bettina
    Karlsruhe Inst Technol, Inst Fluid Mech, D-76131 Karlsruhe, Germany..
    The influence of thermal boundary conditions on turbulent forced convection pipe flow at two Prandtl numbers2019In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 144, article id 118601Article in journal (Refereed)
    Abstract [en]

    Different types of thermal boundary conditions are conceivable in numerical simulations of convective heat transfer problems. Isoflux, isothermal and a mixed-type boundary condition are compared by means of direct numerical simulations (for the lowest Reynolds number) and well-resolved large-eddy simulations of a turbulent forced convection pipe flow over a range of bulk Reynolds numbers from Re-b = 5300 to Re-b = 37700, at two Prandtl numbers, i.e. Pr = 0.71 and Pr = 0.025. It is found that, while for Pr = 0.71 the Nusselt number is hardly affected by the type of thermal boundary condition, for Pr = 0.025 the isothermal boundary condition yields approximate to 20% lower Nusselt numbers compared to isoflux and mixedtype over the whole range of Reynolds numbers. A decomposition of the Nusselt number is derived. In particular, we decompose it into four contributions: laminar, radial and streamwise turbulent heat flux as well as a contribution due to the turbulent velocity field. For Pr = 0.71 the contribution due to the radial turbulent heat flux is dominant, whereas for Pr = 0.025 the contribution due to the turbulent velocity field is dominant. Only at a moderately high Reynolds number, such as Re-b = 37700, both turbulent contributions are of similar magnitude. A comparison of first- and second-order thermal statistics between the different types of thermal boundary conditions shows that the statistics are not only influenced in the near-wall region but also in the core region of the flow. Power spectral densities illustrate large thermal structures in low-Prandtl-number fluids as well as thermal structures located right at the wall, only present for the isoflux boundary condition. A database including the first- and second-order statistics together with individual contributions to the budget equations of the temperature variance and turbulent heat fluxes is hosted in the open access repository KITopen (DOI : https: //doi.org/10.5445/IR/1000096346).

  • 9.
    Villone, Massimiliano M.
    et al.
    Univ Napoli Federico II, Dipartimento Ingn Chim Mat & Prod Ind, Ple Tecchio 80, I-80125 Naples, Italy..
    Rosti, Marco E.
    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.
    Tammisola, Outi
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    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.
    Numerical simulations of oscillatory shear flow of particle suspensions at finite inertia2019In: Rheologica Acta, ISSN 0035-4511, E-ISSN 1435-1528, Vol. 58, no 11-12, p. 741-753Article in journal (Refereed)
    Abstract [en]

    We perform immersed-boundary-method numerical simulations of oscillatory shear flow of suspensions of mono-disperse non-colloidal rigid spherical particles in a Newtonian liquid from the dilute to the concentrated regime. Both small and large amplitude oscillatory shear flow (SAOS and LAOS, respectively) are studied and the effects of particle concentration, fluid inertia, particle-to-fluid density ratio, and deformation amplitude on the measured apparent viscoelastic moduli of the suspensions are quantified. In the SAOS regime, a non-zero storage modulus G '-values significantly change with inertia, but depend on the volume fraction of the solid phase only for suspensions of particles denser than the fluid. On the other hand, the loss modulus G '' increases with both inertia and particle concentration. In the LAOS regime, the moduli are only weakly dependent on the deformation amplitude for a dilute suspension, whereas non-monotonic variations are observed at high concentrations.

  • 10.
    Zhang, Meng
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Naval Systems. KTH Royal Institute of Technology.
    Ice load prediction for design of ice-going ships for inland waterways2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    With increasing interest in utilizing the inland waterways (IWW) in European countries, the design of IWW vessels gains attention both from a transport efficiency and an emission control point of view. However, unlike in western and central European countries, in Nordic countries, e.g. Sweden, IWW ships must deal with ice on the fairway during every winter. Usually, IWW ships are designed without ice concerns and are structurally weaker compared to ships designed according to ice class notification from the classification societies. Developing such ships requires particular concerns since there is no strict requirements regarding ice class notifications for IWW ships. A primary challenge is to estimate both the global and local ice loads acting on the ship hull structure. To consolidate the design problems for IWW ice-going ships, Lake Mälaren is selected. Ice conditions, i.e. ice type and concentration, and ice data, e.g. ice thickness and ice flexural strength, are extracted and analysed for the ice load estimation. The ice mechanical properties have great influence on the ice load. Ice characteristics are studied based on empirical formulae and properties are calibrated by reference data.

    The deterministic approach is widely used to predict the ice loads. It is suitable when all variables, i.e. ship geometry and ice properties, are known and refers to rule-based design hereby. For first year light ice conditions in Lake Mälaren, the Finnish Swedish Ice Class Rule (FSICR) is widely used. The thesis uses guidelines from the Finnish Swedish Ice Class Rules as a reference and compare the results with other methods.

    The probabilistic approach, on contrary, is useful when certain variables are unknow, which are interpreted as random variables, for instance ice breaking pattern. Here the probabilistic method and ice-hull interaction mechanism are studied. The probabilistic method simplifies the ice pressure in relation to the contact area between the ice and the ship hull. It predicts maximum ice pressure acting on the ship hull based on field ice test data and ice exposure conditions. Such semi-empirical method can be used regardless of ship type and size. For this, a numerical model is introduced based on ice-hull collision mechanisms and the essential ice breaking characteristics. The physical mechanism is studied for idealizing ship-ice impact model. The idealization model includes the ice failure process, ice conditions and ship geometry. The ice failure is assumed to be initiated by crushing ice and followed by breaking due to bending failure. Ice properties are set as constant values without any variations. The stochasticity in interact process is represented by randomness in collision location and number of pieces of ice floe formed after breaking. An energy method is used to calculate the ice crushing force, indentation displacement and contact area. The ice bending scenario is simplified as an infinite plate resting on an elastic foundation under a concentrated load. Ice impact load and critical load can be obtained for global and local structural assessment respectively. The structural responses and structural strength of a representative panel at linear and nonlinear contexts are investigated as well. Ship structure is commonly designed with material yield strength as limit. However, the study shows a lighter structure can be achieved if plastic deformation is allowed without causing failure. Therefore, the design can be optimized with regards to ice loading capacity and weight control.

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