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  • 1.
    Barrera Rolla, Leandro
    et al.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland .
    Rice, Henry J.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    Implementation of the forward-advancing wave expansion method (FWEM) for numerical solution of three dimensional large-scale sound propagation problems2007In: 36th International Congress and Exposition on Noise Control Engineering, INTER-NOISE, 2007, Vol. 7, p. 4796-4805Conference paper (Other academic)
    Abstract [en]

    In this paper a “one-way” wave based field discretization method for solving the Helmholtz equation in large-scale problems is proposed and is referred to as the Forward Wave Expansion Method (FWEM). The FWEM is derived from a highly efficient discretization procedure based on the interpolation of wave functions known as the Wave Expansion Method (WEM) and computes the propagated sound field by means of an exclusively forward advancing solution. This technique does not require the inversion of large system matrices and thus enables the solution of large scale acoustic problems where backscatter is not of interest. A computationally light model is thus formulated which retains many advantages of WEM. Accurate results were obtained for a free field sound propagation benchmarking problem. The method was also implemented to successfully model some diffraction effects. The FWEM offers a simple, flexible and efficient discretization method to solve the Helmholtz equation for extensive domains with mesh densities as low as 3 nodes per wavelength. This makes the FWEM a promising method for long range sound propagation problems. 

  • 2.
    Bennett, Gareth J.
    et al.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    O'Reilly, Ciarán J.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    Liu, Hao
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    Tapken, Ulf
    DLR, German Aerospace Center, Germany.
    Modelling multi-modal sound transmission from point sources in ducts with flow using a wave-based method2009In: 16th International Congress on Sound and Vibration, ICSV16, 2009, Vol. 8, p. 4685-4693Conference paper (Other academic)
    Abstract [en]

    An understanding of the multi-modal propagation of acoustic waves in ducts is of practical interest for use in the control of noise in, for example, aero-engines, automotive exhaust and ventilation systems. In this paper, the propagation of sound from point sources in hard-walled ducts is modelled using a numerical wave-based approach, referred to as the wave expansion method. This is a highly efficient full-domain discretisation method, which requires as few as two-to-three mesh points per wavelength. An inhomogeneous potential flow may be easily included in the method. The numerical solution for point sources embedded in the wall of a circular duct with non-reflective end-conditions and a uniform axial flow is compared with an analytical Green's function solution. A modal decomposition technique is used to provide detailed information about the modal content of the sound field. This study provides an insightful comparison between an analytical and numerical solution to the acoustic field in a duct. The accuracy and robustness of the wave expansion method is assessed for this benchmark problem before its versatility is demonstrated with examples.

  • 3.
    Bennett, Gareth J.
    et al.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland .
    O'Reilly, Ciarán
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland .
    Tapken, Ulf
    DLR, German Aerospace Center.
    Fitzpatrick, John A.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland .
    Noise source location in turbomachinery using coherence based modal decomposition2009In: 15th AIAA/CEAS Aeroacoustics Conference (30th AIAA Aeroacoustics Conference), 2009Conference paper (Other academic)
    Abstract [en]

    Coherence based source analysis techniques can be used to identify the contribution of turbomachinery core noise sources to pressure measurements in the far-field. The usual approach is to locate a measurement sensor within the engine and to calculate the ordinary coherence function between this and the far-field pressure measurement. If the internal measurement is close to a dominant noise source, the technique will identify this sources' contribution to the overall far-field energy. Modal decomposition is an advanced technique which can provide detailed information as to the modal content of sound propagating in ducts. When applied to aero-engines, the technique can be used as a diagnostic to determine which of the many rotor-stator stages contribute most to the overall radiated sound power. The method developed in this paper discusses how the two techniques can be combined to locate the plane at which a mode is generated within an aeroengine. A proof of concept of the technique is successfully demonstrated with the use of simulated data.

  • 4.
    Bharath, G.
    et al.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland .
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    Barrera Rolla, Leandro
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    Rice, Henry J.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland .
    Iterative solutions of the three-dimensional Helmholtz equation using the wave expansion method for high frequency acoustic scattering problems2007In: 36th International Congress and Exposition on Noise Control Engineering, INTER-NOISE, 2007, Vol. 7, p. 4788-4795Conference paper (Other academic)
    Abstract [en]

    Modelling sound propagation over large domains presents severe challenges with respect to computational requirements. In general, direct solutions of system equations resulting from the full field discretization of many three-dimensional problems of practical interest cannot be attempted. The present study investigates iterative solutions for solving a Three-Dimensional Helmholtz equation. The discretization of the Helmholtz equation is done by a Wave Based Finite Difference scheme known as the Wave Expansion Method (WEM). The WEM requires only 2-3 nodes per wavelength to obtain accurate solutions which offers a potential for major improvement in efficiency compares to conventional techniques such as the Finite Element/Finite Difference approaches which require around 8-10 nodes per wavelength. The solver employed here is the standard Bi-Conjugate Gradient Stabilized (Bi-CGSTAB) algorithm. Results are presented for high frequency acoustic scattering problems occurring in aircrafts. Investigations are also carried out to check the effectiveness of the standard preconditioning strategies such as the Incomplete LU decomposition with drop tolerance method. The influence of the scatterer is also studied in this paper.

  • 5.
    Bouchouireb, Hamza
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Schöggl, Josef-Peter
    University of Graz, Institute of Systems Sciences Innovation & Sustainability Research, Austria.
    Baumgartner, Rupert J.
    University of Graz, Institute of Systems Sciences Innovation & Sustainability Research, Austria.
    Potting, José
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    The inclusion of vehicle shape and aerodynamic drag estimations within the life cycle energy optimisation methodology2019In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 84, p. 902-907Article in journal (Refereed)
    Abstract [en]

    The present work describes a widening of the scope of the Life Cycle Energy Optimisation (LCEO) methodology with the addition of shape-related design variables. They describe the curvature of a vehicle which impacts its aerodynamic drag and therewith its operational energy demand. Aerodynamic drag is taken into account through the estimation of the drag coefficient of the vehicle body shape using computational fluid dynamics simulations. Subsequently, the aforementioned coefficient is used to calculate the operational energy demand associated with the vehicle. The methodology is applied to the design of the roof of a simplified 2D vehicle model which is both mechanically and geometrically constrained. The roof is modelled as a sandwich structure with its design variables consisting of the material compositions of the different layers, their thicknesses as well as the shape variables. The efficacy of the LCEO methodology is displayed through its ability to deal with the arising functional conflicts while simultaneously leveraging the design benefits of the underlying functional alignments. On average, the optimisation process resulted in 2.5 times lighter and 4.5 times less life cycle energy-intensive free shape designs. This redesign process has also underlined the necessity of defining an allocation strategy for the energy necessary to overcome drag within the context of vehicle sub-system redesign.

  • 6.
    Bouchouireb, Hamza
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Schöggl, Josef-Peter
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. University of Graz, Institute of Systems Sciences Innovation & Sustainability Research, Austria.
    Baumgartner, Rupert J.
    University of Graz, Institute of Systems Sciences Innovation & Sustainability Research, Austria.
    Potting, José
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Towards holistic energy-efficient vehicle product system design: The case for a penalized continuous end-of-life model in the life cycle energy optimisation methodology2019In: 22nd International Conference on Engineering Design, ICED19, Cambridge University Press, 2019, Vol. 1, p. 2901-2910Conference paper (Refereed)
    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. The present work describes the extension of the LCEO methodology to perform holistic product system optimisation. The constrained design of an automotive component and the design of a subset of the processes which are applied to it during its life cycle are simultaneously optimised to achieve a minimal product system life cycle energy. A subset of the processes of the end-of-life phase of a vehicle’s roof are modelled through a continuous formulation. The roof is modelled as a sandwich structure with its design variables being the material compositions and the thicknesses of the different layers. The results show the applicability of the LCEO methodology to product system design and the use of penalisation to ensure solution feasibility.

  • 7.
    Bouchouireb, Hamza
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Pignier, Nicolas
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Boij, Susann
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Dahan, Jeremy A.
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. Siemens PLM, United Kingdom.
    Identification of noise sources on a realistic landing gear using numerical phased array methods applied to computational data2017In: 23rd AIAA/CEAS Aeroacoustics Conference, American Institute of Aeronautics and Astronautics, 2017Conference paper (Other academic)
    Abstract [en]

    The aerodynamic sound sources on a realistic landing gear are investigated using numerical phased array methods, based on array data extracted from compressible Detached-Eddy Simulations of the flow. Assuming monopole or monopole in a moving medium propagation, the sound sources are identified in the source region through various beamforming approaches: dual linear programming (dual-LP) deconvolution, orthogonal beamforming and CLEAN-SC. The predicted source locations are in good agreement with previous experimental results performed on the same nose landing gear configuration by industrial and academic partners within the ALLEGRA project. Additionally, the modeled sources are used to generate far-field spectra which are subsequently compared to the ones obtained with the Ffowcs Williams-Hawkings acoustic analogy. The results of the dual-LP approach show a good match between the far-field spectra up to a certain frequency threshold cor- responding to the quality of the mesh used. The results demonstrate the potential of numerical phased array methods as a legitimate modeling tool for aeroacoustic simulations in general and as a tool to gain insight into the noise generation mechanisms of landing gear components in particular. 

  • 8.
    da Rocha-Schmidt, L.
    et al.
    Technische Universität München, Germany.
    Hermanutz, A.
    Technische Universität München, Germany.
    Baier, H.
    Technische Universität München, Germany.
    Seitz, A.
    Bauhaus Luftfahrt e.V., München, Germany.
    Bijewitz, J.
    Bauhaus Luftfahrt e.V., München, Germany.
    Isikveren, A. T.
    Bauhaus Luftfahrt e.V., München, Germany.
    Scarpa, F. L.
    University of Bristol, UK.
    Allegri, G.
    University of Bristol, UK.
    Remillat, C.
    University of Bristol, UK.
    Feuilloley, E.
    University of Bristol, UK.
    Majic, Frane
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Progress Towards Adaptive Aircraft Engine Nacelles2014In: 29th Congress of the International Council of the Aeronautical Sciences, ICAS, International Council of the Aeronautical Sciences , 2014Conference paper (Other academic)
    Abstract [en]

    Emissions and noise of aircraft engineshave to be significantly further reduced andefficiency further increased in the future. Onemeans is the improvement of airflow though theengine and especially so in its inlet region byproper shapes. Due to changes in the flightconditions, the optimal nacelle shape varies. Itwould thus be beneficial to be able to change thenacelle shape. Evaluations on system and enginelevels including related flow simulations supportthe identification of proper shaping parameters.Initial concepts of possible morphingtechnologies are discussed as well.

  • 9.
    Dahan, Jeremy A.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    O'Reilly, Ciarán
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Numerical investigation of a realistic nose landing gear2014In: 20th AIAA/CEAS Aeroacoustics Conference, American Institute of Aeronautics and Astronautics, 2014Conference paper (Other academic)
    Abstract [en]

    A hybrid approach is used to study the noise generated by a realistic full-scale nose land- ing gear configuration. Compressible Detached-Eddy Simulations are performed to com- pute the flow field and the far-field noise is evaluated with the Ffowcs Williams-Hawkings acoustic analogy. Preliminary Reynolds-Averaged Navier-Stokes simulations are performed to evaluate the sensitivity of the steady solution to the computational grid. It is found that mesh independence is not obtained with the grids considered, although the agreement between the medium and fine grids is reasonable. The time-dependent solution obtained via DES is examined and the main noise sources on the gear surfaces are identified. The power spectral density of pressure uctuations on the tyre surface is found to be rather broadband on the noisier sides of the tyre, while distinct humps and a sharp peak near 1kHz are identified in the quieter regions of the tyre. This sharp peak is observed again in the far-field noise. Further work is needed to clarify the cause of this peak. Its frequency is too high to link it with shedding from a gear component, although it could be associated with unsteadiness near the tyre corner.

  • 10.
    Dahan, Jeremy A.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Numerical investigation of the flow around a realistic nose landing gearManuscript (preprint) (Other academic)
    Abstract [en]

    Detached-eddy simulations of the flow around a realistic two- wheeled nose landing gear are conducted, at a Reynolds number corresponding to the final approach phase for a regional aircraft. The main focus is on the flow and associated sound fields in the inter-wheel region and in the wake of the landing gear. Three unstructured grids are designed to evaluate the sensitivity of the solution to grid resolution. The three flow solutions agree well, although the turbulent wake requires a fine mesh. In addition, comparisons with available experimental data on two other nose landing gear models, the PDCC and LAGOON gears, yield a good qualitative agreement. The wake of the landing gear assembly is strongly three-dimensional and exhibits a complex behaviour. The effect of the torque links and wheel axle on the flow dynamics and sound sources were examined via simulations on different configurations. The presence of the torque links and the wheel axle, often simplified or omitted in numerical landing gear studies, were found to strongly modify the flow in the inter-wheel region and in the wheel wakes. The noise was propagated to the far-field using the convective form of the FWH integral. The far- field noise at sideline receivers agrees well with wind-tunnel measurements and the overhead noise sources in the inter-wheel region are identified by considering the integrand of the FWH analogy. 

  • 11.
    Dahan, Jeremy
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Futrzynski, Romain
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    O'Reilly, Ciarán
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Aero-acoustic source analysis of landing gear noise via dynamic mode decomposition2014In: 21st International Congress on Sound and Vibration, ICSV21: / [ed] Malcolm J. Crocker, Marek Pawelczyk, Jing Tian, 2014, Vol. 2, p. 1245-1252Conference paper (Refereed)
    Abstract [en]

    In this paper, we apply dynamic mode decomposition (DMD) on time accurate simulationsof the pressure distribution on a realistic full-scale noselanding gear configuration in order toidentify noise generating structures on landing gear surfaces. The simulated pressure data isobtained from DES simulations using the commercial software STAR-CCM+ by CD-adapco.The dynamics of the surface pressure on a tyre are discussed and the DMD modes are com-puted from instantaneous pressure snapshots. The far-fieldnoise is determined via the FfowcsWilliams-Hawkings analogy, where a given frequency band source term can be reconstructedby choosing an appropriate number of DMD modes.

  • 12.
    Hammar, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Assembly speed-up for the wave expansion method using a uniform background meshManuscript (preprint) (Other academic)
  • 13.
    Hammar, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Simulation of aerodynamically generated noise propagation using the wave expansion method2016In: 22nd AIAA/CEAS Aeroacoustics Conference, 2016Conference paper (Other academic)
    Abstract [en]

    A numerical method to simulate aerodynamically generated sound and its propagation is presented in this paper. The flow is solved using both analytical expressions and numer- ical methods. The aeroacoustic source terms are then defined by using the aeroacoustic analogies of Lighthill, Ffowcs-Williams and Hawkings, Powell and Howe, and are evaluated from the flow solutions. The acoustic propagation with these sources is then performed using the wave expansion method. This is a discretization method suitable for solving wave propagation through inhomogeneous potential flows. Two different cases are considered in the study, a co-rotating vortex pair and the flow around a 2D cylinder at Re=150. The fo- cus of the work presented is to show a robust introduction of aeroacoustic sources in a wave expansion acoustic propagation solution procedure. The numerical results are compared to experimental and numerical results from other studies of the same configurations. 

  • 14.
    Hammar, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Simulation of aerodynamically generated sound using hybrid aeroacoustic methods2015In: 10th European Congress and Exposition on Noise Control Engineering, Euronoise, 2015, p. 521-526Conference paper (Other academic)
    Abstract [en]

    A numerical method to simulate aerodynamically generated sound and its propagation is presented in this paper. The transient flow field solution is established using a compressible 2D Navier 6WRNHV VROYHU 7KH VRXUFH WHUPV DUH WKHQ GHILQHG E\ XVLQJ +RZH V vortex sound aeroacoustic analogy and are evaluated from the flow solutions. The propagation of acoustic waves from these sources is then performed using the wave expansion method (WEM). This is a discretization method suitable for solving wave propagation through inhomogeneous potential flows. The method is tested on a flow of a rectangular open cavity. The flow conditions are a free stream Mach number of M=0.5 and Reynolds number of Re=1500.. The numerical results are compared to experimental and numerical results from other studies of the same configuration. 

  • 15.
    Jank, Merle-Hendrikje
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Baumgartner, Rupert J.
    University of Graz, Institute of Systems Sciences Innovation & Sustainability Research, Austria.
    Schöggl, Josef-Peter
    University of Graz, Institute of Systems Sciences Innovation & Sustainability Research, Austria.
    Potting, José
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms). PBL Netherlands Environmental Assessment Agency, The Netherlands.
    Advancing energy efficient early-stage vehicle design through inclusion of end-of-life phase in the life cycle energy optimisation methodology2017In: 12th International Conference on Ecological Vehicles and Renewable Energies Conference, EVER, 2017Conference paper (Refereed)
    Abstract [en]

    Environmentally-friendly energy-efficient vehicles are an important contributor to meet future global transportation needs. To minimise the environmental impact of a vehicle throughout its entire life cycle, the life cycle energy optimisation (LCEO) methodology has been proposed. Using the proxy of life cycle energy, this methodology balances the energy consumption of vehicle production, operation and end-of-life scenarios. The overall aim is to design a vehicle where life cycle energy is at a minimum. While previous work only included vehicle production and operation, this paper aims at advancing the LCEO methodology by including an end-of-life phase. A simplified design study was conducted to illustrate how vehicle design changes when end-of-life treatment is included. Landfilling, incineration and recycling have been compared as end-of-life treatments, although the focus was put on recycling. The results reveal that the optimal design not only changes with the inclusion of an end-of-life phase but it changes with specific end-of-life treatment. 

  • 16.
    King, Ulrich
    et al.
    Bauhaus Luftfahrt e.V., Germany.
    Seitz, Arne
    Bauhaus Luftfahrt e.V., Germany.
    Bijewitz, Julian
    Bauhaus Luftfahrt e.V., Germany.
    Hermanutz, Andreas
    Technical University of Munich, Germany.
    da Rocha-Schmidt, Luiz
    Technical University of Munich, Germany.
    Scarpa, Fabrizio
    University of Bristol, United Kingdom.
    Majić, Frane
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Shape adaptive technology for aircraft engine nacelle inlets2016In: The Royal Aeronautical Society's 5th Aircraft Structural Design Conference, 2016Conference paper (Other academic)
    Abstract [en]

    The ambitious emission reduction goals defined by the Advisory Council for Aviation and Innovation in Europe (ACARE), demand new technologies enabling ways to significantly improve aircraft performance. In the European Commission funded low Technology Readiness Level (TRL) project “Morphing Enabling Technologies for Propulsion System Nacelles” (MorphElle) conducted between October 2013 and November 2015, an initial investigation took place to modify the inlet of an Ultra-High Bypass Ratio turbofan nacelle with adaptive structure technology to enhance its aerodynamic performance. The goal was to be able to adopt the inlet lip to different flight conditions and therefore, increase engine performance while at the same time reducing the aerodynamic nacelle drag. A pool of concepts for an adaptive nacelle inlet was established and a down selection was performed and the most promising identified. The selected concept was further elaborated and the impact at aircraft level was examined. Designing an adaptive structure mechanism for the circular shape of a nacelle inlet has different requirements compared to an adaptive structure mechanism, for example, a flap or a slat. For a circular shape, the deformation of the adaptive mechanism in circumferential direction has to be considered as well. A structural concept was established, which consists of flexible outer skin with pneumatic tubes as actuators, which is able to handle the deformation in circumferential direction. With this mechanism it is possible to change the inlet of the used reference nacelle geometry. Numerical tools were used to perform structural and aerodynamic simulations. The results of these simulations served as input for an aircraft assessment. The inputs were nacelle weight, nacelle aerodynamic drag and thrust specific fuel consumption of the engine. With this data an aircraft model was set up and compared to two reference aircraft. The first reference aircraft is a year 2000 reference (comparable to Airbus A330-300). The second reference aircraft is similar to an Airbus A330-300 with projected Entry-Into-Service (EIS) 2025+. For the aircraft equipped with the adaptive nacelle an EIS of 2025+ was assumed as well. The results were that the adaptive nacelle showed improved values for SFC and nacelle aerodynamic drag compared to the reference nacelle geometry. Furthermore, a first prototype of the shape adaptive mechanism as proof of concept was developed. 

  • 17.
    Liu, Hao
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    O'Reilly, Ciarán
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Lopez Arteaga, Ines
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Prediction of sound field in geometrically complex enclosures with the wave expansion methodManuscript (preprint) (Other academic)
  • 18.
    Majić, Frane
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Aero-acoustic performance of adaptive nacelle inlet2015In: 21st AIAA/CEAS Aeroacoustics Conference, 2015Conference paper (Other academic)
    Abstract [en]

    The aero-acoustic investigation of the fan noise propagation is conducted. The fan noise is propagated through the series of adaptive inlet shapes of turbofan engine toward the far field. The inlet shape adaptation is made by changing position of one points on the front part of the inlet contour. The investigation is performed without the influence of the mean flow. The propagation of two acoustic modes was investigated, the combination of first radial mode with first and the second circumferential mode. The intensity and directivity of the fan noise in the far field is observed. A finite element solver for convected Helmholtz equation is used in the inner part of the inlet, with perfectly matched layer boundary condition close to the inlet entrance. The outer part of domain is coupled and solved by Kirchoff integral method. The results showed the influence of the inlet shape adaptation on the noise intensity level as well as the directivity of propagation.

  • 19.
    Majić, Frane
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Aerodynamic performance of the adaptive nacelle inlet2015In: 33rd AIAA Applied Aerodynamics Conference, 2015Conference paper (Other academic)
    Abstract [en]

    The numerical aerodynamic investigations of an adaptive turbofan-engine inlet is per-formed. The adaptation is made on the front inner part of the inlet by changing positionsof two contour knots, which mimic the possible inlet structure morphing. The numericalcalculations are performed using Reynolds Averaged Navier-Stokes (RANS) simulations forthe climb condition. The evaluation of the aerodynamic performance is based on the inlettotal pressure recovery, DC60 parameter and standard deviation of the normal velocity atthe fan plane. The results exhibit common trend which is a shift of the evaluated parame-ters towards benecial level by increasing the radial position of the rst knot at the inletshape region which is close to the leading edge. Alteration of second knot, which is moredistant from leading edge, results in benecial performance for several inlet shapes. For allparameters, the same group of inlet shapes was isolated as a group of best performance.

  • 20.
    Majić, Frane
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Potential improvement of aerodynamic performance by morphing the nacelle inlet2016In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 54, p. 122-131Article in journal (Refereed)
    Abstract [en]

    In this work numerical investigations of the aerodynamic performance of an adaptive turbofan-engine inlet is performed. The adaptation is made on the inner front part of the symmetric inlet by changing the positions of two contour knots, which acts as a possible inlet struc- ture morphing. The contour knots are moved in the axisymmetric and radial directions of the inlet, respectively. The numerical calcula- tions are performed using Reynolds Averaged Navier-Stokes (RANS) simulations and are made for climb and cruise flight conditions. The evaluation of the aerodynamic performance is based on the absolute total pressure recovery at the fan plane. The results show that the adaptation of only a small part of the inlet contour gives benefits in the performance at different flight conditions. The radial position in- crease of the knot closer to the leading edge gives overall increase of the pressure recovery level for both flight conditions. The radial posi- tion change of the knot close to the throat diameter leads to the global maximum of absolute total pressure recovery almost independent of the axial position change of the same knot, for both flight conditions. These maximums are attained at different radial positions of the knot close to the throat diameter, for the two flight conditions.

  • 21.
    Majić, Frane
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    The influence of an adaptive nacelle inlet lip on fan noise propagation2016In: Proceedings of Meetings on Acoustics, ISSN 1939-800X, Vol. 28, no 1, p. 1-10, article id 030004Article in journal (Refereed)
    Abstract [en]

    The aeroacoustic performance of an adaptive inlet of a turbo-fan engine is numerically investigated. The sound intensity and directivity of fan noise propagation to the far-field, and the sound level at lateral reference points are investigated. The investigation is performed for three Helmholtz numbers, with the influence of the mean flow, for a single duct mode. A finite element solver for Helmholtz equation is used in the inner part of the inlet, with a perfectly matched layer boundary condition close to the inlet entrance. The propagation through the outer part of domain is solved by Kirchhoff integral method. The results show the influence of the inlet shape adaptation on the noise intensity level as well as the directivity of propagation. The maximum peak intensity level of all inlet shapes is increased by increasing the Helmholtz number. This causes the width of intensity distribution to become narrower and shifted towards the symmetry axis of the nacelle. The inlet shape with the most opened nacelle throat has the lowest peak and an intensity distribution shifted towards the symmetry axis, which indicates the influence of the mean flow. Also, the more closed nacelle throat causes a decrease of the effective perceived noise level. 

  • 22.
    Majić, Frane
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    The influence of an adaptive nacelle inlet lip on fan noise propagation2016In: 22nd International Congress on Acoustics, 2016Conference paper (Other academic)
    Abstract [en]

    The aeroacoustic performance of an adaptive inlet of a turbo-fan engine is numerically investi- gated in this paper. The sound intensity and directivity of the fan noise propagation to the far-field, and the sound level at lateral reference points are investigated. The investigation is performed for three Helmholtz numbers, with the influence of the mean flow included, for a single duct mode (- 8,1). The contour was defined by five movable knots at the leading edge of the inlet. The contour had to fulfil two constraints, namely it had to have a constant length and a convex curvature. The process of contour adaptation was performed in two steps. In the first step, two knots on the inner inlet side were moved in order to attain a certain shape, while other knots were kept fixed. In the second step, the rest of the knots were moved in order to fulfill the constraints. A finite element solver for the Helmholtz equation is used in the inner part of the inlet, with a perfectly matched layer boundary condition close to the inlet entrance. The propagation through the outer part of domain is solved by Kirchhoff integral method. The results show the influence of the inlet shape adaptation on the noise intensity level as well as the directivity of propagation. The maximum peak intensity level of all inlet shapes is increased by increasing the Helmholtz number. This causes the width of intensity distribution to become narrower and shifted towards the symmetry axis of the nacelle. The inlet shape with the most opened nacelle throat has the lowest peak and an intensity distribution shifted towards the symmetry axis, which indicates the influence of the mean flow. Also, the more closed nacelle throat causes a decrease of the effective perceived noise level. 

  • 23.
    Neri, Eleonora
    et al.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    Kennedy, John
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    Bennett, Gareth J.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    O'Reilly, Ciarán
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Dahan, Jeremy
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Esposito, Marco
    Tecknosud, Italy.
    Bruno, Massimiliano
    Magnaghi Aeronautica, Italy.
    Bianco, Antonello
    Pininfarina, Italy.
    Amoroso, Francesco
    Eurotech, Italy.
    Di Giulio, Massimiliano
    Allenai Aermacchi, Italy.
    Characterization of low noise technologies applied to a full scale fuselage mounted nose landing gear2015In: 44th International Congress and Exposition on Noise Control Engineering, INTER-NOISE, The American Society of Mechanical Engineers (ASME) , 2015, Vol. 3, p. 1869-1878Conference paper (Other academic)
    Abstract [en]

    The negative impact of aircraft noise includes effects on population's health, land use planning and economic issues such as building restrictions and operating restrictions for airports. Thus, the reduction of noise generated by aircraft at take-off and approach is an essential consideration in the development of new commercial aircraft. Among the different aircraft noise sources, landing gear noise is one of the most significant during approach. This research presents results from the European Clean Sky funded ALLEGRA project, which investigated a full-scale Nose Landing Gear (NLG) model featuring the belly fuselage, bay cavity and hydraulic dressing. Tests were performed for a variety of wind speeds and yaw angles. In this paper, a characterization of the noise generated by the full-scale Nose Landing Gear (NLG) model is presented and the different techniques used for characterizing acoustic sources on the NLG are described. The landing gear noise source is characterized in terms of OASPL, directivity, source spectra, PNL and PNLT. A comparison between the NLG with and without the application of low noise technology is presented.

  • 24.
    Nygren, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Boij, Susann
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Rumpler, Romain
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    A study of the interaction between vehicle exterior noise emissions and vehicle energy demands for different drive cycles2019In: 23rd International Congress on Acoustics, ICA, 2019Conference paper (Other academic)
    Abstract [en]

    This initial study investigates the interaction between vehicle noise emissions and the energy required to move the vehicles along different drive cycles. There is a trade-off between reducing noise emissions and at the same time reducing other environmental impacts. A vehicle's energy demand associated with a specific drive cycle may be affected when a different route is chosen between two locations to reduce the noise exposure at certain observer points. The methodology of the study was to use the existing IMAGINE traffic noise model as a source model, and to evaluate the sound exposure level (SEL) at observer points as a function of instantaneous sound pressure level estimates as the source moved from one location to another via two different routes. A noise impact estimate with a linear dependence on the difference between the SEL and a threshold level was proposed. Also, the energy demand for each route was calculated. The results indicated that there is a difference between the two routes if the aim is to reduce the noise exposure or the energy demand. Suggested future research is to further improve the noise impact evaluations in the context of very short durations of exposure.

  • 25.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    A wave expansion method for acoustic propagation in lined flow ducts2015In: Applied Acoustics, ISSN 0003-682x, Vol. 90, p. 54-63Article in journal (Refereed)
    Abstract [en]

    Acoustic liners are used extensively in engineering applications, particularly in aero-engines and automotive exhaust systems. In this paper, a flow impedance boundary conditions is introduced into the wave expansion method with the aim of providing an efficient methodology for computing the acoustic propagation through a lined duct with flow. For a potential flow, the boundary layer and the lined wall are included in the discretisation scheme by the Myers flow impedance boundary condition. The acoustic propagation through a flow impedance tube is computed in order to validate the implementation of the impedance boundary condition in this scheme. The results show that this computationally light methodology provides generally good agreement with the experimental data.

  • 26.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Acoustic propagation in a lined duct using a wave expansion method2012In: 41st International Congress and Exposition on Noise Control Engineering, INTER-NOISE, Institute of Noise Control Engineering (INCE) , 2012, Vol. 8, p. 6577-6587Conference paper (Other academic)
    Abstract [en]

    Acoustic liners are used extensively in engineering applications, particularly in aero-engines. Liners are characterised by a complex impedance, which is dependent on the grazing flow velocity and acoustic pressure spectrum at the liner surface. The acoustic propagation through a lined duct is examined in this paper using a wave expansion method. This is a highly efficient full domain discretisation method, based on interpolation of plane wave functions, which is suitable for solving a convected Helmholtz equation. For a potential flow, the boundary layer and the lined wall are included in the numerical scheme by the Myers boundary condition. This assumes that the acoustic pressure and particle velocity are continuous across a thin boundary layer. The acoustic propagation through a flow-impedance tube is computed in order to validate the implementation of the impedance boundary condition in this scheme. Good agreement with the experimental data from the literature is shown.

  • 27.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Creative engineers: Is abductive reasoning encouraged enough in degree project work?2016In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 50, p. 547-552Article in journal (Refereed)
    Abstract [en]

    Creativity is considered to be an important ability for an engineer to have, and it is therefore important that the development of this ability is structured into the education of engineering students, along with the ability to apply, analyse and evaluate based on existent knowledge. In this paper, the importance of abduction in creative engineering processes is briefly reviewed. It has been shown that abductive reasoning plays a key role in design as it is the only logical operation that introduces new ideas. Its encouragement within the KTH Royal Institute of Technology's degree projects at the Department of Aeronautical and Vehicle Engineering is analysed by examining the stated intended learning outcomes, and through interviewing students. It is found that abductive reasoning is not explicitly encouraged within the intended learning outcomes of these degree project courses, despite its importance in creative thinking. Although, it is very likely that at least some abduction takes place in the project work, its absence from the intended learning outcomes means that students may not have a felt need to demonstrate their abductive reasoning, and supervisors may encourage only non-creative deductive or inductive reasoning. A more explicit inclusion of abductive reasoning in the intended learning outcomes would help both students and supervisors to include creative thinking in the degree project courses. 

  • 28.
    O'Reilly, Ciarán J.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering.
    On the acoustics of installed subsonic jets2009Doctoral thesis, monograph (Other academic)
  • 29.
    O'Reilly, Ciarán J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Alenius, Emma
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Bodony, D. J.
    University of Illinois Urbana-Champaign, USA.
    Aero-acoustic simulations of an orifice plate mounted in a low-Mach-number ducted flow2012In: 18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference), 2012Conference paper (Other academic)
    Abstract [en]

    Aero-acoustic simulations are performed for an orifice plate mounted in a straight duct in a low-Mach number flow. A two-dimensional flow-field is calculated by solv- ing the Navier-Stokes equations by means of a large-eddy simulation (LES), using a high-order finite difference scheme. The scheme uses summation-by-parts (SBP) finite difference operators with simultaneous approximation terms (SAT) to impose boundary conditions. The flow is decomposed using dynamic mode decomposition (DMD) in order to gain insight into the generation of sound by the flow. The frequency of the higher amplitude modes is shown to agree well the frequencies of the highest amplitude peaks in the power spectral density of the outgoing acoustic waves.

  • 30.
    O'Reilly, Ciarán J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Alenius, Emma
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Bodony, Daniel J.
    University of Illinois Urbana-Champaign, USA.
    Numerical simulation of flow-induced sound generation from an orifice in a low Mach number ducted flow2011In: 17th AIAA/CEAS Aeroacoustics Conference (32nd AIAA Aeroacoustics Conference), 2011Conference paper (Other academic)
    Abstract [en]

    Aero-acoustic simulations are performed for an orifice plate mounted in a straight duct in a low-Mach number flow. The flow field is calculated by solving the filtered Navier-Stokes equations by means of direct numerical simulation (DNS), using a high-order finite difference scheme. The scheme uses summation-by-parts (SBP) finite difference operators with simultaneous approximation terms (SAT) to impose boundary conditions. Both the scattering of the sound (passive part) as well as the sound generation (active part) are studied in the low frequency plane wave range. An acoustic two-port model is applied to describe the sound in the duct. The results are compared with experimental data for the same configuration. The efficiency and robustness of the numerical technique are also examined.

  • 31.
    O'Reilly, Ciarán J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Dazel, Olivier
    Université du Maine, Laboratoire d'Acoustique de l'Université du Maine, France.
    A wave expansion method for sound absorbing materials2015In: 22nd International Congress on Sound and Vibration, ICSV22, 2015, Vol. 4, p. 2797-2804Conference paper (Refereed)
    Abstract [en]

    In this paper, a wave expansion method is developed to predict the absorption of sound in poro- elastic materials. Poroelastic materials are often used in noise control applications where they are connected to a fluid medium in order dissipate acoustic waves through viscous, thermal and structural effects. The efficient numerical modelling of sound propagation in such materials is therefore of practical interest for many engineering applications. A wave expansion method is de- veloped here to model the propagation through coupled fluid and poroelastic materials. The wave expansion method uses fundamental solutions of the wave operator and so accurate solutions to linearised propagation equations may be obtained with only two-to-three points per wavelength, which is significantly less than the six-to-ten points per wavelength needed for comparable tra- ditional finite difference and finite element methods. The method is also robust to meshing and could be implemented in a meshless manner. These characteristics make it well suited to examin- ing sound absorption applications. The method is applied to a benchmark problem and the results are compared to the analytical solution. The method is found to be very promising. 

  • 32.
    O'Reilly, Ciarán J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Dazel, Olivier
    Université du Maine, Laboratoire d'Acoustique de l'Université du Maine, France..
    Gabard, Gwénaël
    Université du Maine, Laboratoire d'Acoustique de l'Université du Maine, France..
    Numerically solving the biot equations for sound absorbing materials using a wave expansion method2018In: 47th International Congress and Exposition on Noise Control Engineering, INTER-NOISE, Institute of Noise Control Engineering , 2018Conference paper (Refereed)
    Abstract [en]

    Poroelastic materials are often used in noise control applications to dissipate acoustic waves through viscous, thermal and structural effects. The prediction of sound propagation in such materials is therefore of practical interest for many engineering applications. This propagation may be described by the Biot equations. In this paper, a numerical approach known as a wave expansion method is developed to solve the Biot equations. A wave expansion method uses fundamental solutions of the wave operator and so accurate solutions to linearised propagation equations may be obtained with only two-to-three points per wavelength. The method is also robust to meshing and could be implemented in a meshless manner. These characteristics make it well suited to examining practical sound absorption applications. The method is applied to a benchmark problem and the results are compared to the analytical solution. The results are found to behave consistently at mid-to-high frequencies, but there is an increasing error due to ill-conditioning at low frequencies. 

  • 33.
    O'Reilly, Ciarán J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Hammar, Johan
    Creo Dynamics AB.
    Emborg, Urban
    Creo Dynamics, Sweden.
    Numerical investigation of self-sustained shock oscillation acoustics2012In: 10th International Conference on Flow-Induced Vibration and Flow-Induced Noise, FIV / [ed] Meskell & Bennett, FIV , 2012, p. 681-688Conference paper (Other academic)
    Abstract [en]

    A numerical investigation of the sound resultant from a compressible flow about an 18% thick circular-arc aerofoil, for free-stream Mach numbers between M = 0.7 and M = 0.82, and a Reynolds number Re ~ 10^7, is presented in this paper. Within this range of parameters, self-sustained shock oscillations may be present on the upper and lower aerofoil surfaces. The transient flow-field was computed by detached-eddy simulation, with the solution used to quantify acoustic sources, defined by Howe's analogy, that are propagated using a wave expansion method. The results were compared with available experimental and numerical results from other studies of the same configuration.

  • 34.
    O'Reilly, Ciarán J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Hammar, Johan
    Creo Dynamics, Sweden.
    Emborg, Urban
    Creo Dynamics, Sweden.
    Persson, Andreas
    Creo Dynamics, Sweden.
    An Investigation into Shock Oscillation Noise Reduction2013In: 4th CEAS Air and Space Conference, 2013Conference paper (Other academic)
    Abstract [en]

    Self-sustained shock-oscillations were investigated in this work, with a view to implementing countermeasures to stop the motion of the shock and, therefore, to reduce the associated noise. The transonic flow past a symmetric airfoil was computed using computational fluid dynamics. A number of potential countermeasures were also included in the simulations in order identify the relative importance of their physical parameters in reducing the shock motion. 

  • 35.
    O'Reilly, Ciarán J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Economic and ecological influences on the design and adoption of new vehicle concepts2016In: 22nd International Sustainable Development Research Society Conference, ISDRS, 2016, Vol. 2, p. 413-420Conference paper (Refereed)
    Abstract [en]

    Integration of economic and ecological considerations with engineering ones in new vehicle concepts presents many challenges, not least of which is overcoming long established expectations of vehicles and their performance. Design choices are not only influenced by clear rational factors but also by many imperfectly rational ones, which interact in a complex way to shape the final vehicle artefact. It should therefore be of interest to model and explore how such factors interact and influence the design process, particularly when it comes to targeting limited resources towards achieving the maximum improvement in the design. The aim is to find out under what circumstances can specific improvements penetrate into the established vehicle design and where are the critical phase boundaries over which significant advancement may be achieved. This is especially relevant in light of the on-going adoption of new technologies aimed at reducing the environmental impacts of vehicles. This insight may enable the design and adoption of radically different vehicles that represent a tipping point for sustainable transportation. A methodology is introduced to dynamically explore the trade-offs in vehicle design. The engineered vehicle is recognised as being a sub-system within a much wider surrounding world. A broad model is introduced to include both rational performance properties and imperfectly rational forces, and the system is stepped forward in time. The methodology is applied to a case study in which new knowledge is introduced into the established design paradigm and its adoption is tracked under a number of starting conditions and assumptions. The results illustrate where a targeted improvement that compensates for inherent inertia may lead to greater adoption that is beneficial from a broader long-term perspective. The model behaves reasonably in the vicinity of boundary conditions but more work is needed to explore and refine the behaviour across multiple variables. 

  • 36.
    O'Reilly, Ciarán J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Funazaki, Atsushi
    Japan Automobile Research Institute.
    Suzuki, Tetsuya
    Japan Automobile Research Institute.
    Edlund, Stefan
    Volvo Group Trucks Technology.
    Gunnarsson, Cecilia
    Volvo Group Trucks Technology.
    Lundow, Jan-Olov
    Bombardier Transportation.
    Cerin, Pontus
    Swedish Energy Agency.
    Cameron, Christopher J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. Swerea SICOMP.
    Wennhage, Per
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Potting, José
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms). PBL Netherlands Environmental Assessment Agency.
    Life-cycle energy optimisation: A proposed methodology for integrating environmental considerations early in the vehicle engineering design process2016In: Journal of Cleaner Production, ISSN 0959-6526, Vol. 135, p. 750-759Article in journal (Refereed)
    Abstract [en]

    To enable the consideration of life cycle environmental impacts in the early stages of vehicle design, a methodology using the proxy of life cycle energy is proposed in this paper. The trade-offs in energy between vehicle production, operational performance and end-of-life are formulated as a mathematical problem, and simultaneously balanced with other transport-related functionalities, and may be optimised. The methodology is illustrated through an example design study, which is deliberately kept simple in order to emphasise the conceptual idea. The obtained optimisation results demonstrate that there is a unique driving-scenario-specific design solution, which meets functional requirements with a minimum life cycle energy cost. The results also suggest that a use-phase focussed design may result in a solution, which is sub-optimal from a life cycle point-of-view.

  • 37.
    O'Reilly, Ciarán J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Potting, José
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Cameron, Christopher J.
    Swerea SICOMP, Sweden.
    Wennhage, Per
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Life-cycle energy optimisation for sustainable vehicle design2014In: FISITA World Automotive Congress, 2014Conference paper (Other academic)
    Abstract [en]

    A methodology is presented in this paper, in which the trade-offs in energy between vehicle production, operational performance and end-of-life are formulated as a mathematical problem that may be optimised. This methodology enables the consideration of the life-cycle environmental impact, through the proxy of life-cycle energy, in the very first stages of transport vehicle design where it can be concurrently balanced with other functionalities. The methodology is illustrated through a sandwich panel design case study. The optimisation results for this case demonstrate that a design solution does exist, which meets functional requirements with a minimum life-cycle energy cost. They also highlight that a pure lightweight design may result in a solution, which is sub-optimal from a life cycle point-of-view. 

  • 38.
    O'Reilly, Ciarán J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aeroacoustics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Rice, Henry J.
    Trinity College, Dublin, Ireland.
    A Lighthill based jet noise model for acoustic shielding prediction2010In: 17th International Congress on Sound and Vibration, ICSV17: Volume 1, 2010, p. 558-565Conference paper (Other academic)
    Abstract [en]

    The majority of research on jet noise has considered isolated shear-flows and, as such, jet noise models based on Lighthill's acoustic analogy traditionally assume a free-space Green's function for propagation. In order to evaluate the reduction in jet noise attainable from proposed airframe shielding configurations, a jet noise model based on Lighthill's analogy is derived in this paper, which retains an explicit Green's function in the expression for the far-field spectral density. This Green's function may be evaluated to include the diffraction of the sound field about an acoustic shield. A preliminary comparison is made with the limited data available for shielded jets. In addition to facilitating the study of shielding configurations, isolated predictions made using this model compare favourably with isolated jet noise data.

  • 39.
    O'Reilly, Ciarán J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Rice, Henry J.
    Trinity College, Dublin, Ireland.
    An Assessment of Jet Noise Shielding Prediction Parameters2010In: 16th AIAA/CEAS Aeroacoustics Conference (31st AIAA Aeroacoustics Conference), 2010Conference paper (Other academic)
    Abstract [en]

    On-going research and development by the European aeronautical community towards the reduction of civil aircraft noise has been investigating the shielding of engine noise sources by airframe components (wing/fuselage/empennage). In order to assess the noise reduction benefits attainable from such novel configurations, it is necessary to develop appropriate acoustic evaluation tools. In this paper, the Tam-Auriault jet noise model, with a RANS solution input, in conjunction with a Fresnel-Kirchhoff diffraction method is used to make isolated and shielded far-field jet noise predictions. This methodology is employed as a sensitivity analysis tool in order to establish the relative importance of the source location, spatial extent and directivity in jet noise shielding predictions.

    Although, the predicted isolated jet directivity agrees well with far-field empirical values, the predicted levels of shielding are much larger than those observed in the available data. A preliminary investigation into the possible causes of this discrepancy indicates that the introduction of the shield adjacent to the jet may result in the generation of new ‘installation sources’, which limit the shielding achievable in practical applications.

  • 40.
    O'Reilly, Ciarán J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aeroacoustics.
    Rice, Henry J.
    Trinity College, Dublin, Ireland.
    Investigation of a jet-noise-shielding methodology2015In: AIAA Journal, ISSN 0001-1452, E-ISSN 1533-385X, Vol. 53, no 11, p. 3286-3296Article in journal (Refereed)
    Abstract [en]

    Ongoing research toward the reduction of environmental noise from aircraft is investigating the possible shielding of engine-noise sources by novel airframe configurations. To assess the noise-reduction benefits attainable from such configurations, it is necessary to develop appropriate acoustic evaluation tools. In this paper, a jet-noise-shielding- prediction methodology is described. The Tam–Auriault (“Jet Mixing Noise from Fine-Scale Turbulence,” AIAA Journal, Vol. 37, No. 2, 1999, pp. 145–153) jet-noise model with a Reynolds-averaged Navier–Stokes solution input, together with a Fresnel–Kirchhoff diffraction method (Fundamentals of Physical Acoustics, Wiley-Interscience, New York, 2000, pp. 472–494), is used to make isolated and shielded far-field jet-noise predictions. This methodology is employed as a sensitivity-analysis tool to establish the relative importance of the source location, spatial extent, and directivity in jet-noise-shielding predictions. Predictions have been made for a shielded single-stream Mach 0.9 jet, and compared with experimental data. Good qualitative agreement is observed, and the disagreement in the shielding levels is most likely due to underestimation of the source axial extent by the jet-noise model. 

  • 41.
    O'Reilly, Ciarán J.
    et al.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    Rice, Henry J.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    Jet noise modelling for shielding calculations using RANS solution source localisation and WEM propagation2006In: 22nd International Conference on Noise and Vibration Engineering, ISMA, Leuven University Press, 2006, p. 667-676Conference paper (Other academic)
    Abstract [en]

    In this paper, a method to determine the jet noise source input for shielding calculations is described. The method involves three steps - localisation, propagation and simplification. Firstly, for the frequency of interest, a small localised source region is determined, using Goldstein-Rosenbaum's acoustic model, with a numerical RANS solution providing local flow properties. A number of distinct incoherent noise sources may be located in this region, using the turbulence length scales. In the second step, each source is propagated out through the jet flow using the wave expansion method (WEM) to solve the Helmholtz equation, with local Mach values acquired from the RANS solution. The third step is to define a Kirchhoff surface outside the jet flow, from which the sound may be propagated further by simply using the Helmholtz-Kirchhoff integral, which can account for any mean flow present. Although the method is quite crude, it is relatively robust as it is a shielding factor or ratio, rather than an absolute value, which is of interest in design evaluation. Preliminary results, presented in this paper, provide encouragement that this new three-step jet noise source modelling method can be used to provide a source input for use in airframe shielding calculations, that is equivalent - in terms of source frequency, distribution and directivity - to the noise produced by a jet flow.

  • 42.
    O'Reilly, Ciarán J.
    et al.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland .
    Rice, Henry J.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    Jet noise modelling for shielding calculations using RANS source localisation and WEM propagation2006In: 8th International Symposium Transport Noise and Vibration, 2006Conference paper (Other academic)
    Abstract [en]

    In this paper, a method to determine the jet noise source input for shielding calculations is described. The method involves three steps – localisation, propagation and simplification. Firstly, for the frequency of interest, a small, localised source region is determined, using Goldstein-Rosenbaums’ acoustic model, with a numerical RANS solution providing local flow properties. A number of distinct incoherent noise sources may be located in this region, using the turbulence length scales. In the second step, each source is propagated out through the jet flow using the wave expansion method (WEM) to solve the Helmholtz equation, with local Mach values acquired from the RANS solution. The third step is to define a Kirchhoff surface outside the jet flow, from which, the sound may be propagated further by simply using the Helmholtz-Kirchhoff integral equation, which, can account for any mean flow present. This method is relatively robust, as it is a shielding factor or ratio, rather than an absolute value, which is of interest in acoustic design evaluation. Preliminary results, presented in this paper, provide encouragement that this new three-step jet noise source modelling method can be used to provide a source input for use in airframe shielding calculations, that is equivalent – in terms of source frequency, distribution and directivity – to the noise produced by a jet flow. 

  • 43.
    O'Reilly, Ciarán J.
    et al.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    Rice, Henry J.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland.
    Jet noise shielding: Mean flow convection and refraction effects on jet noise source propagation2008In: 23rd International Conference on Noise and Vibration Engineering, ISMA, Leuven University Press, 2008, p. 525-533Conference paper (Other academic)
    Abstract [en]

    Positioning aircraft engines on the rear of the fuselage above a U-shaped empennage, is an aircraft configuration, which could possibly reduce the engine noise emitted towards the ground during take-off and approach. In order to acoustically assess the shielding effect attained from such a configuration, the complicated physical noise sources must, firstly, be represented in a manner appropriate for input into propagation / shielding prediction methods. In this paper, the development of an innovative methodology for providing such a source for jet noise is described. Convecting point sources are located using Lighthill's analogy with a Reynolds-Averaged Navier Stokes (RANS) solution to provide mean flow properties. The refractive effect of the mean jet flow on sound propagation is determined using a Wave Expansion Method (WEM) to efficiently numerically propagate monopole noise sources in a small domain, which includes the sheared jet flow. This near-field WEM result is then propagated to the far-field using the Helmholtz-Kirchhoff integral equation, assuming a uniform flow external to the Kirchhoff surface. The refractive flow effect on omnidirectional sources is superimposed on the convecting sources. These directional point sources may be used as a sound source input for shielding prediction methods. In this present study, jet noise sources have been created for a range of frequencies. The isolated sound pressure level and the shielding effect, resultant from separating these sources from an arc of receivers, with a flat plate, have been evaluated and results compared with test data. Results presented here are very encouraging, as they clearly indicate that with the inclusion of both the convective and the refractive effects of the jet flow on the propagation of point sources, simple jet noise sources may be defined for use in shielding prediction methods, however, using the present approximations, the predicted sound pressure levels are greater than the measured values at downstream receiver angles.

  • 44.
    O'Reilly, Ciarán J.
    et al.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland .
    Rice, Henry J.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland .
    Bharath, G.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland .
    Barrera Rolla, L.
    Trinity College Dublin, Department of Mechanical and Manufacturing Engineering, Ireland .
    An investigation into the effects of engine body reflections and flow refraction on jet noise shielding predictions2007In: 36th International Congress and Exhibition on Noise Control Engineering, INTER-NOISE, 2007, Vol. 2, p. 733-742Conference paper (Other academic)
    Abstract [en]

    Airframe acoustic shielding predictions, using simple point sources located over an isolated wing, tend to over-predict shielding effects, when compared with full-model test data. The study presented in this paper investigates the effects of the inclusion of the engine body and the jet flow on shielding predictions. A wave expansion method (WEM), is used to efficiently model the sound propagation, in a small domain which includes the wing and engine body. In this model the jet is still represented as point sources. A 2d model is examined, in which the mean jet flow has been included. The point source locations and strengths are determined using a RANS solution of a hot coaxial jet and Goldstein's interpretation of the acoustic analogy. The near-field WEM results are then propagated to the far-field using the Helmholtz-Kirchhoff integral equation, which assumes a uniform flow external to the Kirchhoff surface. Results presented here are very encouraging as they clearly indicate that with the inclusion of engine body reflections, and the refractive effects of the jet flow, predicted shielding values are much more consistent with observed levels both in terms of magnitude and variation over observation angle.

  • 45.
    Pascual José, Borja
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    A study of the viscous effects over an acoustic liner using the linearised Navier-Stokes equations in the frequency domain2017In: 23rd AIAA/CEAS Aeroacoustics Conference, American Institute of Aeronautics and Astronautics, 2017Conference paper (Other academic)
    Abstract [en]

    Noise regulations for civil aviation restrict the sound level that engines can emit to a great extent. Acoustic liners are the most widespread solution in order to damp sound in aircraft engines. Usually the linearised Euler equations (LEE) are used to calculate the sound propagation through the engine and the near wall effects introduced by the presence of the boundary layer are accounted by the Myers boundary condition. Nonetheless, this boundary condition has been proved to be ill-posed and to generate numerical instabilities, and thus, the boundary layer is not being properly described by this model. Hence, in this paper a different approach is taken by using the linearised Navier-Stokes equations and avoiding the Myers boundary condition since a viscous solution is adopted. The RANS equation and a frequency domain are used to calculate the flow and the acoustic fields respectively, in an attempt to reduce the high computational cost associated with this type of simulation. In order to assess the validity of this method a computational study is developed and the results are then compared to a benchmark case. Good agreement with the benchmark data is found, therefore showing the validity of this methodology. 

  • 46.
    Pignier, Nicolas
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Dahan, Jeremy
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    O'Reilly, Ciarán
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Boij, Susann
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Aeroacoustic analysis of a NACA duct2015In: 10th European Congress and Exposition on Noise Control Engineering, Euronoise, 2015Conference paper (Other academic)
    Abstract [en]

    An initial aeroacoustic study of a typical NACA inlet is presented. In this paper, the shape of the NACA inlet is based on the experimental work of the National Advisory Committee for Aeronautics. The study is performed at low Mach numbers. A time-averaged solution is obtained through a RANS simulation and validated against experimental results. The results show good agreement both in terms of overall performance of the inlet and in terms of local surface pressures. From the steady simulations, a broadband noise source model is applied to get an estimate of the location of the noise source regions on the surface of the inlet. This model of the NACA inlet will be used for a future acoustic analysis based on unsteady detached eddy simulation (DES) of the flow and on the Ffwocs Williams-Hawkings integral.

  • 47.
    Pignier, Nicolas J.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Boij, Susann
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    A Kirchhoff approximation-based numerical method to compute multiple acoustic scattering of a moving source2015In: Applied Acoustics, ISSN 0003-682x, Vol. 96, p. 108-117Article in journal (Refereed)
    Abstract [en]

    Within the scope of a study of external noise propagation from moving ground vehicles, a numerical method is developed to compute the acoustic field emitted by a moving source in the presence of scattering objects such as roads, buildings or noise-shields. This method is developed with the purpose of being used in a vehicle design process and therefore it must have a low computational cost, which requires a certain number of approximations. The case of a fixed point source is studied first then the effect of a movement of the source is taken into account through the introduction of a retarded time. The acoustic source is assumed to be represented by one or many harmonic monopoles of possibly different frequency moving with a constant speed in a quiescent flow field. Scattering from nearby perfectly reflecting objects is computed through a Kirchhoff–Helmholtz integral equation applying the Kirchhoff approximation. A ray-surface intersection algorithm to compute shadow areas is proposed. The method is validated against analytical solutions and experimental results for a fixed source, and against a higher-order finite difference time-domain method for the multiple scattering of a moving source. Results are good and show that this method can potentially be used to predict urban noise.

  • 48.
    Pignier, Nicolas
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Boij, Susann
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Aerodynamic and aeroacoustic analyses of a submerged air inlet in a low-Mach-number flow2016In: Computers & Fluids, ISSN 0045-7930, E-ISSN 1879-0747, Vol. 133, p. 15-31Article in journal (Refereed)
    Abstract [en]

    Computational aerodynamic and aeroacoustic analyses of a submerged air inlet are performed at a low Mach number. A hybrid method is used, in which the flow in the vicinity of the inlet is solved through detached eddy simulation (DES) and the acoustic pressure in the far-field is computed through the use of a Ffowcs Williams and Hawkings integral. Several surfaces of integration are used, both solid and permeable. The inlet design is based on an experimental inlet developed by the National Advisory Committee for Aeronautics (NACA). The flow is solved first through steady-state RANS simulation, then time-dependent DES is run from the converged results. The results from both RANS simulations and DES show good agreement with experimental data from NACA, both in terms of integral quantities and surface pressure coefficients. Pressure fluctuations are observed on both sides of the lip of the inlet, and are greater at low velocity ratios, with the velocity ratio defined as the ratio between the flow velocity at the duct entrance and in the free stream. A transition is observed between a quasi-laminar flow at a velocity ratio of 0.8 and a turbulent flow at velocity ratios of 0.6 and 0.4. This turbulent behaviour at low velocity ratios is associated with much higher acoustic levels in the far-field. At low velocity ratios, the acoustic spectra in the far-field exhibit a broadband character with maximum levels distributed around a characteristic frequency given by the ratio between the flow velocity at the duct entrance and the duct entrance depth. At high velocity ratios, the spectra show tonal characteristics with peaks at around 90 percent of this characteristic frequency and at the corresponding harmonics. A comparison between the spectra from solid and permeable surfaces reveals that volume sound sources are negligible at this low Mach number. A visualization of the integrands in the Ffowcs Williams and Hawkings integral show that sound sources are located on both sides of the lip of the inlet, at the position of impact of the vortices, and along the vortex wakes. Some observations regarding the use of solid and permeable surfaces of integration are made.

  • 49.
    Pignier, Nicolas
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Boij, Susann
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Une Méthode Numérique pour Calculer la Diffusion Acoustique d’une Source Mobile par Plusieurs Objets2014In: 12e Congrès Français d'Acoustique, 2014Conference paper (Other academic)
    Abstract [en]

    As part of a study of external noise propagation from moving ground vehicles, a numerical method is developed to compute the acoustic field emitted by a moving point source and its interaction with a near environment constituted of buildings or noise barriers for example. This method is developed with the purpose of being used in a vehicle design process therefore it must be low demanding on computational resources. This requires approximations. The problem is simplified to that of a constant speed moving harmonic monopole point source passing by one or more perfectly reflecting large objects in a quiescent flow field. The simpler case of a fixed point source is studied first. Reflections on nearby objects are computed through a Kirchhoff-Helmholtz integral equation to which is applied the Kirchhoff approximation, assuming the regime of high frequencies. Multiple scattering is computed by consecutive updates of surface pressure values. The effect of a movement of the source is accounted for through the introduction of a Doppler shift in the Kirchhoff-Helmhotlz equation. This method is validated against experimental results from literature for a case of simple scattering of a sound wave emitted by a fixed source and against results from a higher-order finite difference time-domain solver in case of multiple scattering of the sound wave emitted by a moving point source. Results are satisfying for the foreseen use of this method. 

  • 50.
    Pignier, Nicolas
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Boij, Susann
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Aeroacoustic study of a submerged air inlet using an IDDES/FW-H approach and sound source modelling through direct numerical beamforming2016In: 22nd AIAA/CEAS Aeroacoustics Conference, American Institute of Aeronautics and Astronautics, 2016Conference paper (Other academic)
    Abstract [en]

    The flow-generated sound from an air inlet at a low Mach number is studied using detached eddy simulation and direct numerical beamforming. The flow is solved through RANS and compressible detached eddy simulation for various velocity ratios, defined as the ratio between the flow speed at the duct entrance and in the free stream. Results for the flow show very good agreement with experimental data from the National Advisory Committee for Aeronautics (NACA). Pressure data is extracted at the position of a virtual microphone array inside the simulation domain, outside of the unsteady flow region. The array data is beamformed on a source test grid over the inlet using standard beamforming and Linear Programming deconvolution approaches. As beamforming is performed from simulated data directly in the acoustically resolved domain, the method is referred to as Direct Numerical Beamforming (DNB). The results give information about the location, amplitude and frequency content of the sound sources around the inlet. The resulting incoherent sound sources can be used as a model for the sound radiated from the inlet. Using a simple Green's function, the corresponding far-field spectrum is computed for two velocity ratios, showing a very good agreement with the spectra obtained from a Ffowcs Williams and Hawkings integral.

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