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Rynell, A., Chevalier, M., Åbom, M. & Efraimsson, G. (2018). A numerical study of noise characteristics originating from a shrouded subsonic automotive fan. Applied Acoustics, 140, 110-121
Open this publication in new window or tab >>A numerical study of noise characteristics originating from a shrouded subsonic automotive fan
2018 (English)In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 140, p. 110-121Article in journal (Refereed) Published
Abstract [en]

The characteristics of the noise radiated from a reduced automotive cooling module are numerically studied focusing on the interaction effects linked to the sound generation mechanisms and the acoustic scattering caused by the confined installation. The flow field is simulated by adopting the formulation of Improved Delayed Detached Eddy Simulation (IDDES), which is a numerical technique that enables large-scale structures to be resolved and the wall-bounded flow to be treated depending on the turbulent content within the boundary layer. By comparing the simulated fan performance to two sets of measurement data of a similar setup, the aerodynamic results obtained from IDDES are validated and conformed to the volumetric flow rate delivered for the pressure drop measured. The acoustic part of the study comprises evaluation of the sound source associated with the momentum distribution imposed on the surroundings at an interface slightly upstream of the fan. At the microphone positions upstream of the installation, the SPL falls within the SPL range measured and the acoustic power delivered by the fan conforms to the SWL obtained from the comparison method in the reverberation room. The system response function, estimated by subtracting the SWL for the free-field simulation from the SWL associated with the reduced automotive cooling module marks spectral humps at fixed frequencies, irrespectively of sound source. As such, the engineering approach to the spectral decomposition method earlier published, which enables the acoustical properties of the installation to be isolated from the source, is validated and found to hold.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Aeroacoustics, Fan noise, IDDES, Installation effects, Spectral decomposition
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-228690 (URN)10.1016/j.apacoust.2018.05.006 (DOI)000440121900012 ()2-s2.0-85047243465 (Scopus ID)
Note

QC 20180529

Available from: 2018-05-29 Created: 2018-05-29 Last updated: 2018-08-20Bibliographically approved
Rynell, A., Efraimsson, G., Chevalier, M. & Åbom, M. (2016). Acoustic characteristics of a heavy duty vehicle cooling module. Applied Acoustics, 111, 67-76
Open this publication in new window or tab >>Acoustic characteristics of a heavy duty vehicle cooling module
2016 (English)In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 111, p. 67-76Article in journal (Refereed) Published
Abstract [en]

Studies dedicated to the determination of acoustic characteristics of an automotive cooling package are presented. A shrouded subsonic axial fan is mounted in a wall separating an anechoic- and a reverberation room. This enables a unique separation of the up- and downstream sound fields. Microphone measurements were acquired of the radiated sound as a function of rotational speed, fan type and components included in the cooling module. The aim of the present work is to investigate the effect of a closely mounted radiator upstream of the impeller on the SPL spectral distribution. Upon examination of the SPL spectral shape, features linked specifically to the source and system are revealed. The properties of a reverberant sound field combined with the method of spectral decomposition permit an estimation of the source spectral distribution and the acoustic transfer response, respectively. Additionally, purely intrinsic acoustic properties of the radiator are scrutinized by standardized ISO methods. A new methodology comprising a dipole sound source is adopted to circumvent limitation of transmission loss measurement in the low frequency range. The sound attenuation caused by the radiator alone was found to be negligible.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Fan noise, Insertion loss, Installation effects, Spectral decomposition, Transmission loss, Acoustic field measurement, Acoustic fields, Acoustic properties, Acoustics, Architectural acoustics, Cooling, Fans, Insertion losses, Radiators, Reverberation, Wave transmission, Acoustic characteristic, Heavy duty vehicles, Reverberation rooms, Spectral distribution, Audio signal processing
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-186888 (URN)10.1016/j.apacoust.2016.04.004 (DOI)000377837700008 ()2-s2.0-84962788665 (Scopus ID)
Note

QC 20160524

Available from: 2016-05-24 Created: 2016-05-16 Last updated: 2017-11-30Bibliographically approved
Na, W., Boij, S. & Efraimsson, G. (2016). Acoustic characterization of a hybrid liner consisting of porous material by using a unified linearized navier-stokes approach. In: 22nd AIAA/CEAS Aeroacoustics Conference, 2016: . Paper presented at 22nd AIAA/CEAS Aeroacoustics Conference, 2016, 30 May 2016 through 1 June 2016. American Institute of Aeronautics and Astronautics
Open this publication in new window or tab >>Acoustic characterization of a hybrid liner consisting of porous material by using a unified linearized navier-stokes approach
2016 (English)In: 22nd AIAA/CEAS Aeroacoustics Conference, 2016, American Institute of Aeronautics and Astronautics, 2016Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, the acoustic properties of a hybrid liner placed at the end of an impedance tube are investigated using numerical simulations. The hybrid liner constitutes of three components, a perforated plate, a porous layer and a rectangular back cavity. The presence of the porous layer is to enhance the absorptive performance of a liner. The main objective of the paper is to verify the proposed numerical methodology - a unified linearized Navier-Stokes Equations (LNSE) approach. In the unified LNSE approach, the combination of the Helmholtz Equation, LNSE as well as the equivalent fluid model are solved in different regions of the impedance tube. To achieve this, the continuity of the coupling condition between the LNSE and the Helmholtz equation is examined. Another objective is to analyze the effectiveness of the porous material to the acoustic performance of the liner. Acoustic liner simulations with and without porous material, porous material with different flow resistivity are carried out. A good agreement is found between the numerical results and the measurements previously performed at KTH MWL.1 Compared to previous work234, several improvements have been made in the numerical methodology, such as that the energy equation has been added in order to include the damping due to viscous dissipation as well as the thermal dissipation in the vicinity of the perforated plate.

Place, publisher, year, edition, pages
American Institute of Aeronautics and Astronautics, 2016
Keywords
Acoustic impedance, Acoustic properties, Aeroacoustics, Characterization, Helmholtz equation, Linearization, Numerical methods, Oil well casings, Perforated plates, Porous materials, Viscous flow, Acoustic characterization, Acoustic performance, Coupling condition, Linearized Navier-Stokes, Linearized navier-stokes equations, Numerical methodologies, Thermal dissipation, Viscous dissipation, Navier Stokes equations
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-194621 (URN)10.2514/6.2016-2980 (DOI)2-s2.0-84982871151 (Scopus ID)978-1-62410-386-5 (ISBN)
Conference
22nd AIAA/CEAS Aeroacoustics Conference, 2016, 30 May 2016 through 1 June 2016
Note

Conference Paper. QC 20161101

Available from: 2016-11-01 Created: 2016-10-31 Last updated: 2019-03-19Bibliographically approved
Rasam, A., Botha, J. D. M., Karl, B., O'Reilly, C. J., Efraimsson, G. & Rice, H. J. (2016). Aerodynamic noise prediction for a wind turbine using numerical flow simulations and semi-empirical modelling approaches. In: 22nd AIAA/CEAS Aeroacoustics Conference: . Paper presented at 22nd AIAA/CEAS Aeroacoustics Conference, 2016, Lyon, France, 30 May 2016 through 1 June 2016,. American Institute of Aeronautics and Astronautics
Open this publication in new window or tab >>Aerodynamic noise prediction for a wind turbine using numerical flow simulations and semi-empirical modelling approaches
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2016 (English)In: 22nd AIAA/CEAS Aeroacoustics Conference, American Institute of Aeronautics and Astronautics, 2016Conference paper, Published paper (Other academic)
Abstract [en]

In this paper, aerodynamic and aero-acoustic simulations are performed for a small horizontal axis wind turbine, suitable for the integration of wind energy in urban and peri-urban areas. Detached-eddy simulation (DES) of compressible flow is performed to compute the flow field over the wind turbine. The far-field noise is computed using the Ffowcs - Williams and Hawkings acoustic analogy. Furthermore, the blade element momentum theory is used with a semi-empirical acoustic modeling approach to predict the wind turbine noise. The acoustic modeling approach is based on a semi-empirical formulation for airfoil self noise and an analytic formulation for inflow noise.

Place, publisher, year, edition, pages
American Institute of Aeronautics and Astronautics, 2016
Keywords
Acoustic noise, Aeroacoustics, Aerodynamics, Turbomachine blades, Wind power, Acoustic analogy, Aero-acoustic simulation, Aerodynamic noise, Blade element momentum theory, Detached eddy simulations, Horizontal axis wind turbines, Numerical flow simulations, Wind turbine noise
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-185035 (URN)10.2514/6.2016-2846 (DOI)2-s2.0-85057294577 (Scopus ID)
Conference
22nd AIAA/CEAS Aeroacoustics Conference, 2016, Lyon, France, 30 May 2016 through 1 June 2016,
Note

QC 20160613

Available from: 2016-04-08 Created: 2016-04-08 Last updated: 2019-03-19Bibliographically approved
Muld, T. W., Efraimsson, G., Henningson, D. S., Herbst, A. H. & Orellano, A. (2016). Analysis of flow structures in the wake of a high-speed train. In: Proceedings aerodynamics of heavy vehicles III, buses, trucks and trains: . Paper presented at Aerodynamics of heavy vehicles III: Trucks, buses and trains, September 12-17, Potsdam, Germany, 2010. Springer, 79
Open this publication in new window or tab >>Analysis of flow structures in the wake of a high-speed train
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2016 (English)In: Proceedings aerodynamics of heavy vehicles III, buses, trucks and trains, Springer, 2016, Vol. 79Conference paper, Published paper (Refereed)
Abstract [en]

Slipstream is the flow that a train pulls along due to the viscosity of the fluid. In real life applications, the effect of the slipstream flow is a safety concern for people on platform, tracksideworkers and objects on platforms such as baggage carts and pushchairs. The most important region for slipstream of high-speed passanger trains is the near wake, in which the flow is fully turbulent with a broad range of length and time scales. In this work, the flow around the Aerodynamic Train Model (ATM) is simulated using Detached Eddy Simulation (DES) to model the turbulence. Different grids are used in order to prove grid converged results. In order to compare with the results of experimental work performed at DLR on the ATM, where a trip wire was attached to the model, it turned out to be necessary to model this wire to have comparable results. An attempt to model the effect of the trip wire via volume forces improved the results but we were not successful at reproducing the full velocity profiles. The flow is analyzed by computing the POD and Koopman modes. The structures in the floware found to be associated with two counter rotating vortices. A strong connection between pairs of modes is found, which is related to the propagation of flow structures for the POD modes. Koopman modes and POD modes are similar in the spatial structure and similarities in frequencies of the time evolution of the structures are also found.

Place, publisher, year, edition, pages
Springer, 2016
Series
Lecture Notes in Applied and Computational Mechanics, ISSN 1613-7736
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-65755 (URN)10.1007/978-3-319-20122-1_1 (DOI)2-s2.0-84951325441 (Scopus ID)978-331920121-4 (ISBN)
External cooperation:
Conference
Aerodynamics of heavy vehicles III: Trucks, buses and trains, September 12-17, Potsdam, Germany, 2010
Note

QC 20160202

Available from: 2012-01-25 Created: 2012-01-25 Last updated: 2016-09-05Bibliographically approved
Winkler, N., Drugge, L., Stensson Trigell, A. & Efraimsson, G. (2016). Coupling aerodynamics to vehicle dynamics in transient crosswinds including a driver model. Computers & Fluids, 138, 26-34
Open this publication in new window or tab >>Coupling aerodynamics to vehicle dynamics in transient crosswinds including a driver model
2016 (English)In: Computers & Fluids, ISSN 0045-7930, E-ISSN 1879-0747, Vol. 138, p. 26-34Article in journal (Refereed) Published
Abstract [en]

In this paper we assess the order of model complexity needed to capture a vehicle behaviour during a transient crosswind event, regarding the interaction of the aerodynamic loads and the vehicle dynamic response. The necessity to perform a full dynamic coupling, including feedback in real-time, instead of a static coupling to capture the vehicle performance both with respect to aerodynamics and the vehicle dynamics is evaluated. The computations are performed for a simplified bus model that is exposed to a transient crosswind. The aerodynamic loads are obtained using Detached Eddy Simulation (DES) with the overset mesh technique coupled to a single-track model for the vehicle dynamics including a driver model with three sets of controller parameters to obtain a realistic scenario. Two degrees of freedom are handled by the vehicle dynamics model; lateral translation and yaw motion. The results show that the full dynamic coupling is needed for large yaw angles of the vehicle, where the static coupling over-predicts the aerodynamic loads and in turn the vehicle motion. © 2016 Elsevier Ltd

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Aerodynamics, Crosswind, Dynamic coupling, Overset mesh, Vehicle dynamics
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-195240 (URN)10.1016/j.compfluid.2016.08.006 (DOI)000384866500003 ()2-s2.0-84982113221 (Scopus ID)
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note

QC 20161117

Available from: 2016-11-17 Created: 2016-11-02 Last updated: 2017-11-29Bibliographically approved
Nair, V., Alenius, E., Boij, S. & Efraimsson, G. (2016). Inspecting sound sources in an orifice-jet flow using Lagrangian coherent structures. Computers & Fluids, 140, 397-405
Open this publication in new window or tab >>Inspecting sound sources in an orifice-jet flow using Lagrangian coherent structures
2016 (English)In: Computers & Fluids, ISSN 0045-7930, E-ISSN 1879-0747, Vol. 140, p. 397-405Article in journal (Refereed) Published
Abstract [en]

A novel method is proposed to identify flow structures responsible for sound generation in confined flow past an inhibitor. Velocity fields obtained using Large Eddy Simulations (LES) are post-processed to compute the Finite Time Lyapunov Exponent (FTLE) field, the ridges of which in backward time represent an approximation to Lagrangian Coherent Structures (LCS), the structures that organize transport in the flow field. The flow-field is first decomposed using dynamic mode decomposition (DMD), and the organizing centers or vortices at the significant DMD frequencies are extracted. The results are then compared with the lambda(2) criterion. Features such as shear layer roll-up and development of secondary instabilities are more clearly visible in the FTLE field than with the lambda(2) criterion.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Aeroacoustics, Large eddy simulation (LES), Lagrangian coherent structures (LCS), Finite time Lyapunov exponents (FTLE), Dynamic mode decomposition (DMD)
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-197766 (URN)10.1016/j.compfluid.2016.09.001 (DOI)000388048400032 ()2-s2.0-84992663769 (Scopus ID)
Note

QC 20161229

Available from: 2016-12-29 Created: 2016-12-08 Last updated: 2017-06-28Bibliographically approved
Na, W., Efraimsson, G. & Boij, S. (2016). Numerical prediction of thermoacoustic instabilities with a V-Flame. In: 23rd International Congress on Sound and Vibration 2016 (ICSV 23), Athens, Greece 10-14 July 2016, Volume 1 of 6: From Ancient to Modern Acoustics. Paper presented at 23rd International Congress on Sound and Vibration 2016 (ICSV 23), Athens, Greece 10-14 July 2016. International Institute of Acoustics and Vibrations, 1
Open this publication in new window or tab >>Numerical prediction of thermoacoustic instabilities with a V-Flame
2016 (English)In: 23rd International Congress on Sound and Vibration 2016 (ICSV 23), Athens, Greece 10-14 July 2016, Volume 1 of 6: From Ancient to Modern Acoustics, International Institute of Acoustics and Vibrations , 2016, Vol. 1Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, results from a numerical solver for the Helmholtz equation using the Finite Element Method (FEM) for predicting thermoacoustic instabilities are presented. The one-dimensional n-τ flame model, which is governed by an interaction index n and a time-delay τ as well as a Flame transfer function (FTF) is used for flame source term. We show results for the validation of the numerical solver for the Rijke tube benchmark case with the variation of n and τ in the one-dimensional n-τ model. Thereafter, thermoacoustic instabilities for a V-flame are predicted, for a typical configuration of a dump combustor - a tube with an area expansion. This is a more realistic test case, since a bluff-body flame holder is often used in combustors, where a V-flame will be generated and anchored to the rod. Usually, the V-flame is more susceptible to thermoacoustic instabilities. In the paper, the eigenfrequencies, as well as the acoustic pressure perturbations are presented as numerical results.

Place, publisher, year, edition, pages
International Institute of Acoustics and Vibrations, 2016
Keywords
Acoustics, Combustors, Numerical methods, Thermoacoustics, Time delay, Acoustic pressures, Eigen frequencies, Flame transfer functions, Interaction index, Numerical predictions, Numerical results, Numerical solvers, Thermoacoustic instability, Finite element method
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-195437 (URN)2-s2.0-84987864236 (Scopus ID)978-1-5108-2716-5 (ISBN)
Conference
23rd International Congress on Sound and Vibration 2016 (ICSV 23), Athens, Greece 10-14 July 2016
Note

Funding Details: FP7-PEOPLE-ITN-2012, EC, European Commission

QC 20161128

Available from: 2016-11-28 Created: 2016-11-03 Last updated: 2019-02-28Bibliographically approved
Majić, F., Efraimsson, G. & O'Reilly, C. J. (2016). Potential improvement of aerodynamic performance by morphing the nacelle inlet. Aerospace Science and Technology, 54, 122-131
Open this publication in new window or tab >>Potential improvement of aerodynamic performance by morphing the nacelle inlet
2016 (English)In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 54, p. 122-131Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Aerodynamics, Nacelle inlet, Turbo-fan engine, Total pressure recovery, Morphing geometry
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-182666 (URN)10.1016/j.ast.2016.04.006 (DOI)000378441000011 ()2-s2.0-84964786323 (Scopus ID)
Note

QC 20160420

Available from: 2016-02-22 Created: 2016-02-22 Last updated: 2017-11-30Bibliographically approved
Hammar, J., O'Reilly, C. J. & Efraimsson, G. (2016). Simulation of aerodynamically generated noise propagation using the wave expansion method. In: 22nd AIAA/CEAS Aeroacoustics Conference: . Paper presented at 22nd AIAA/CEAS Aeroacoustics Conference, 30 May - 1 June 2016, Lyon, France.
Open this publication in new window or tab >>Simulation of aerodynamically generated noise propagation using the wave expansion method
2016 (English)In: 22nd AIAA/CEAS Aeroacoustics Conference, 2016Conference paper, Published 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. 

National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-185032 (URN)10.2514/6.2016-3024 (DOI)2-s2.0-85057294323 (Scopus ID)9781624103865 (ISBN)
Conference
22nd AIAA/CEAS Aeroacoustics Conference, 30 May - 1 June 2016, Lyon, France
Note

QC 20160613

Available from: 2016-04-08 Created: 2016-04-08 Last updated: 2019-06-17Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-9061-4174

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