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Peerlings, L., Boij, S. & Bodén, H. (2019). Experimental investigation of the aero-acoustic interaction at an area-expansion. Journal of Sound and Vibration, 457, 197-211
Open this publication in new window or tab >>Experimental investigation of the aero-acoustic interaction at an area-expansion
2019 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 457, p. 197-211Article in journal (Refereed) Published
Abstract [en]

Experimental results on the aero-acoustic interaction at an area expansion are scarce. In this study, new experimental data is acquired of the aero-acoustic interaction at an area expansion and compared with recent modeling efforts. The aero-acoustic interaction at an area expansion with expansion ratio eta = 0.309 is investigated by measuring the scattering matrix for plane waves at 5 different flow speeds in the incompressible regime. The experimental results are complimented with a comprehensive uncertainty analysis to determine the precision of the data. The scattering coefficients together with derived quantities such as absorption coefficients and dimensionless end corrections are compared against recent analytical results. It is shown that there is consistent deviation between the models and measurement results for certain scattering coefficients. The measured end correction on Strouhal number close to the critical Strouhal number shows a relatively abrupt change. This in comparison with the models, where the change is predicted to be more gradual. Similar observations are made for the absorption coefficient for waves incident upstream of the area expansion, although a qualitative comparison is difficult to make in this case because of the strong influence of the flow downstream of the area-expansion on the results.

Place, publisher, year, edition, pages
Academic Press, 2019
Keywords
Area expansion, Acoustic-flow interaction, Kutta condition, Scattering matrix
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-255351 (URN)10.1016/j.jsv.2019.04.003 (DOI)000474195900012 ()2-s2.0-85067206353 (Scopus ID)
Note

QC 20190730

Available from: 2019-07-30 Created: 2019-07-30 Last updated: 2019-07-30Bibliographically approved
Surendran, A., Heckl, M. A., Peerlings, L., Boij, S., Bodén, H. & Hirschberg, A. (2018). Aeroacoustic response of an array of tubes with and without bias-flow. Journal of Sound and Vibration, 434, 1-16
Open this publication in new window or tab >>Aeroacoustic response of an array of tubes with and without bias-flow
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2018 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 434, p. 1-16Article in journal (Refereed) Published
Abstract [en]

Heat exchangers, consisting of tube arrays in a cross-flow are a vital component of power generation systems. They are of interest from an acoustic point of view, because they can reflect, transmit and absorb an incident sound wave; in other words, they have the potential to act as a sound absorber and even as a passive control device to prevent a thermoacoustic instability in the power generation system. This paper presents a fundamental study of the aeroacoustic response of a tube array with and without bias-flow (also called cross-flow). The study has a theoretical and experimental side. On the theoretical side, a new model, based on the assumption of quasi-steady flow, was developed to predict the acoustic reflection and transmission coefficient of a tube array with bias-flow. Also, the model by Huang and Heckl (Huang and Heckl, 1993, Acustica 78, 191-200) for the case without bias-flow was evaluated. On the experimental side, flow-duct experiments using a multi-microphone technique were performed to validate the predictions from both models. The agreement was found to be very good for low frequencies. The measurements revealed the limit of validity of the quasi-steady model in terms of the Strouhal number. Although this limit is quite low, our quasi-steady model can serve as a valuable tool for designers of heat exchangers.

Place, publisher, year, edition, pages
Academic Press, 2018
Keywords
Aeroacoustics, Low-frequency response, Tube array, Heat exchanger, Low mach number bias-flow, Duct flow
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-235429 (URN)10.1016/j.jsv.2018.07.022 (DOI)000444001700001 ()2-s2.0-85050697044 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme
Note

QC 20180927

Available from: 2018-09-27 Created: 2018-09-27 Last updated: 2018-09-27Bibliographically approved
Peerlings, L., Bake, F., Boij, S. & Bodén, H. (2018). Assessing the stochastic error of acoustic scattering matrices using linear methods. INTERNATIONAL JOURNAL OF SPRAY AND COMBUSTION DYNAMICS, 10(4), 380-392
Open this publication in new window or tab >>Assessing the stochastic error of acoustic scattering matrices using linear methods
2018 (English)In: INTERNATIONAL JOURNAL OF SPRAY AND COMBUSTION DYNAMICS, ISSN 1756-8277, Vol. 10, no 4, p. 380-392Article in journal (Refereed) Published
Abstract [en]

To be able to compare the measured scattering matrices with model predictions, the quality of the measurements has to be known. Uncertainty analyses are invaluable to assess and improve the quality of measurement results in terms of accuracy and precision. Linear analyses are widespread, computationally fast and give information of the contribution of each error source to the overall measurement uncertainty; however, they cannot be applied in every situation. The purpose of this study is to determine if linear methods can be used to assess the quality of acoustic scattering matrices. The uncertainty in measured scattering matrices is assessed using a linear uncertainty analysis and the results are compared against Monte-Carlo simulations. It is shown that for plane waves, a linear uncertainty analysis, applied to the wave decomposition method, gives correct results when three conditions are satisfied. For higher order mode measurements, the number of conditions that have to be satisfied increases rapidly and the linear analysis becomes an unsuitable choice to determine the uncertainty on the scattering matrix coefficients. As the linear uncertainty analysis is most suitable for the plane wave range, an alternative linear method to assess the quality of the measurements is investigated. This method, based on matrix perturbation theory, gives qualitative information in the form of partial condition numbers and the implementation is straightforward. Using the alternative method, the measurements of higher order modes are analyzed and the observed difference in the measured reflection coefficients for different excitation conditions is explained by the disparity in modal amplitudes.

Place, publisher, year, edition, pages
SAGE PUBLICATIONS INC, 2018
Keywords
Uncertainty analysis, higher order modes, sensitivity analysis, partial condition numbers, in-duct acoustics
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-241016 (URN)10.1177/1756827718789066 (DOI)000453453000010 ()2-s2.0-85058573682 (Scopus ID)
Note

QC 20190108

Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-01-08Bibliographically approved
Bodén, H., Khodashenas, N. S. & Boij, S. (2018). Experimental study of nonlinear acoustic properties of perforates using band-limited random excitation information. In: 25th International Congress on Sound and Vibration 2018, ICSV 2018: Hiroshima Calling. Paper presented at 25th International Congress on Sound and Vibration 2018: Hiroshima Calling, ICSV 2018, Hiroshima, Japan, 8 July 2018 through 12 July 2018 (pp. 1818-1825). International Institute of Acoustics and Vibration, IIAV, 3
Open this publication in new window or tab >>Experimental study of nonlinear acoustic properties of perforates using band-limited random excitation information
2018 (English)In: 25th International Congress on Sound and Vibration 2018, ICSV 2018: Hiroshima Calling, International Institute of Acoustics and Vibration, IIAV , 2018, Vol. 3, p. 1818-1825Conference paper, Published paper (Refereed)
Abstract [en]

Perforates are used for noise control in automotive mufflers and aircraft engine liners as well as for other vehicles and machines. Their acoustic properties and noise reduction are known to depend on the mean flow field and other parameters such as temperature and acoustic excitation level. It is therefore of interest to understand how the properties of perforates varies with the level of acoustic excitation. This paper gives an overview of high level nonlinear effects on the acoustic properties of perforates. It includes semi-empirical models as well as experimental studies. Methods for studying nonlinear effects and harmonic interaction effects, for perforates, using single tone excitation and Poly-harmonic distortion models or nonlinear scattering matrices are discussed. These techniques typically require measurements with a number of different acoustic loads. It would be more attractive to directly be able to extract the nonlinear acoustic properties from a more limited set of experiments using either random or periodic excitation. Multi input - single output techniques for nonlinear system identification using broadband random excitation has been tried with limited success. One reason is the mixing of the sound pressure signal incident from the acoustic source with the sound pressure transferred to higher frequencies by nonlinear effects at the perforate sample. The present paper includes an attempt to combine band-limited broadband excitation with Poly-harmonic distortion models or nonlinear scattering matrices describing the nonlinear transfer of energy to higher frequencies.

Place, publisher, year, edition, pages
International Institute of Acoustics and Vibration, IIAV, 2018
Keywords
Acoustic properties, Aeroacoustics, Nonlinear system identification, Perforates
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-241887 (URN)2-s2.0-85058683457 (Scopus ID)9781510868458 (ISBN)
Conference
25th International Congress on Sound and Vibration 2018: Hiroshima Calling, ICSV 2018, Hiroshima, Japan, 8 July 2018 through 12 July 2018
Note

QC 20190125

Available from: 2019-01-25 Created: 2019-01-25 Last updated: 2019-01-25Bibliographically approved
Pignier, N., O'Reilly, C. J. & Boij, S. (2017). Identifying equivalent sound sources from aeroacoustic simulations using a numerical phased array. Journal of Sound and Vibration, 394C, 203-219
Open this publication in new window or tab >>Identifying equivalent sound sources from aeroacoustic simulations using a numerical phased array
2017 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 394C, p. 203-219Article in journal (Refereed) Published
Abstract [en]

An application of phased array methods to numerical data is presented, aimed at identifying equivalent flow sound sources from aeroacoustic simulations. Based on phased array data extracted from compressible flow simulations, sound source strengths are computed on a set of points in the source region using phased array techniques assuming monopole propagation. Two phased array techniques are used to compute the source strengths: an approach using a Moore-Penrose pseudo-inverse and a beamforming approach using dual linear programming (dual-LP) deconvolution. The first approach gives a model of correlated sources for the acoustic field generated from the flow expressed in a matrix of cross- and auto-power spectral values, whereas the second approach results in a model of uncorrelated sources expressed in a vector of auto-power spectral values. The accuracy of the equivalent source model is estimated by computing the acoustic spectrum at a far-field observer. The approach is tested first on an analytical case with known point sources. It is then applied to the example of the flow around a submerged air inlet. The far-field spectra obtained from the source models for two different flow conditions are in good agreement with the spectra obtained with a Ffowcs Williams-Hawkings integral, showing the accuracy of the source model from the observer's standpoint. Various configurations for the phased array and for the sources are used. The dual-LP beamforming approach shows better robustness to changes in the number of probes and sources than the pseudo-inverse approach. The good results obtained with this simulation case demonstrate the potential of the phased array approach as a modelling tool for aeroacoustic simulations.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
sound sources, modelling, phased array, beamforming, simulations, dual-LP beamforming
National Category
Fluid Mechanics and Acoustics
Research subject
Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-192164 (URN)10.1016/j.jsv.2017.01.051 (DOI)2-s2.0-85011589602 (Scopus ID)
Note

QC 20160921

Available from: 2016-09-06 Created: 2016-09-06 Last updated: 2017-11-21Bibliographically approved
Yanaz Çınar, Ö., Boij, S., Çınar, G. & Nilsson, B. (2017). Sudden area expansion in ducts with flow – A comparison between cylindrical and rectangular modelling. Journal of Sound and Vibration, 396, 307-324
Open this publication in new window or tab >>Sudden area expansion in ducts with flow – A comparison between cylindrical and rectangular modelling
2017 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 396, p. 307-324Article in journal (Refereed) Published
Abstract [en]

The acoustic properties of an area expansion are analyzed for frequencies where flow acoustic interaction may have a significant influence due to flow separation and vortex shedding. It is investigated why this interaction, which is seen in experimental data on a cylindrical duct as a resonance at a particular Strouhal number of order one, is present in rectangular but not in cylindrical modelling that would be expected to be more realistic; both models consider a plug flow. An analytic method that is suitable for identifying possible reasons for the discrepancies between the two geometries is used. The previously published rectangular model is generalized to the cylindrical case and both models are used to simulate results for all elements in the plane wave scattering matrix and for all parameters for which experimental results are available. The comparison between the two models and between models and measured data is thus not restricted to the flow acoustic induced resonance. The results show that the two geometries in general perform equally when compared with the experimental results, but that the rectangular modelling indeed performs better for some cases. This occurs around a critical Strouhal number, and for higher Mach number. Using the analytic form of the solution, it is shown that the observed discrepancy is related to interaction between the damped hydrodynamic mode and a downstream propagating higher order acoustic mode. Such interaction is not present in the corresponding quiescent duct, and is related to the presence of the shear layer. The analysis shows that the structure of the higher order acoustic modes is different for the cylindrical and rectangular case, respectively, causing the difference in resonant behaviour.

Place, publisher, year, edition, pages
Academic Press, 2017
Keywords
Building block method, Jet pipe, Sudden area expansion, Wiener-Hopf technique, Acoustic properties, Ducts, Flow separation, Strouhal number, Analytic method, Cylindrical ducts, Flow acoustics, Flow-acoustic interaction, Hydrodynamic modes, Plane-wave scattering, Wiener-Hopf techniques, Fighter aircraft
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-207317 (URN)10.1016/j.jsv.2017.02.034 (DOI)000399507200017 ()2-s2.0-85014754083 (Scopus ID)
Note

QC 20170609

Available from: 2017-06-09 Created: 2017-06-09 Last updated: 2017-06-09Bibliographically approved
Färm, A., Boij, S., Glav, R. & Dazel, O. (2016). Absorption of sound at a surface exposed to flow and temperature gradients. Applied Acoustics, 110, 33-42
Open this publication in new window or tab >>Absorption of sound at a surface exposed to flow and temperature gradients
2016 (English)In: Applied Acoustics, ISSN 0003-682x, Vol. 110, p. 33-42Article in journal (Other academic) Published
Abstract [en]

In noise abatement using porous or fibrous materials, accurate determination of the surface impedance representing the absorber is decisive for simulation quality. The presence of grazing flow and non-homogeneous ambient temperature influence the reaction of the absorber and may suitably be included in a modified “effective” surface impedance. In this paper, this approach is applied to a generic case representative for the engine bay of a heavy truck, where porous shields suppress the radiated noise, e.g. during a pass-by noise test. The change in the absorption is determined numerically by solving the wave propagation through a layer of varying temperature and flow adjacent to the impedance surface for different angles of incidence. The study shows significant impact of both flow and temperature, especially for materials with low absorption. The diffuse field absorption coefficient is also derived and although the effect is less pronounced in this case, it is still important in lower frequencies and in the frequency range typical for IC engine noise. The proposed numerical method is shown to be accurate and efficient for determination of the effective impedance and moreover not limited to thin boundary layers.

Place, publisher, year, edition, pages
Elsevier, 2016
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-183440 (URN)10.1016/j.apacoust.2016.03.017 (DOI)000377232500005 ()2-s2.0-84977634166 (Scopus ID)
Note

QC 20160407

Available from: 2016-03-11 Created: 2016-03-11 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
Surendran, A., Heckl, M. A., Boij, S., Bodén, H. & Hirschberg, A. (2016). Aeroacoustic response of an array of tubes with bias-flow. In: ICSV 2016 - 23rd International Congress on Sound and Vibration: From Ancient to Modern Acoustics. Paper presented at 23rd International Congress on Sound and Vibration, ICSV 2016, 10 July 2016 through 14 July 2016. International Institute of Acoustics and Vibrations
Open this publication in new window or tab >>Aeroacoustic response of an array of tubes with bias-flow
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2016 (English)In: ICSV 2016 - 23rd International Congress on Sound and Vibration: From Ancient to Modern Acoustics, International Institute of Acoustics and Vibrations , 2016Conference paper, Published paper (Refereed)
Abstract [en]

Heat exchanger tube bundles, consisting of tube arrays in cross flows, are vital in the efficient working of power generation systems. If sound propagates through these bundles, it can lead to resonance or acoustic attenuation, and thereby affecting the working of the power generation unit. Therefore, it is important to study the aeroacoustics of tube rows. The aim of the present work is to experimentally validate the quasi-steady compressible model developed to study the aeroa-coustic response of an array of tubes with bias flow. In order to accomplish this, the array of tubes is approximated by a geometry consisting of two half cylinders separated by a gap and having a bias flow through the gap. Firstly, the case with no flow is considered and the experimental results for the reflection and transmission coefficients are compared against the analytical expressions developed by Huang and Heckl (Huang and Heckl, 1993, Acustica 78, 191-200). Then the cases with flow are considered. A quasi-steady subsonic compressible model is developed to predict the reflection and transmission coefficients, valid for low Strouhal numbers, with the additional assumption of small Helmholtz number and low Mach numbers. This model is validated against the experimental results for the transmission and reflection coefficients. A two-port multi-microphone measurement technique is used to obtain the pressure data and a subsequent wave decomposition is utilised to extract the transmission and reflection coefficients. The results show good agreement with theory for various Mach numbers, in the low Strouhal number regime.

Place, publisher, year, edition, pages
International Institute of Acoustics and Vibrations, 2016
Keywords
Aeroacoustics, Aerodynamics, Mach number, Reflection, Strouhal number, Acoustic attenuation, Aeroacoustic response, Analytical expressions, Measurement techniques, Power generation systems, Power generation units, Reflection and transmission coefficients, Transmission and reflection coefficient, Tubes (components)
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-195538 (URN)000388480402122 ()2-s2.0-84987925199 (Scopus ID)9789609922623 (ISBN)
Conference
23rd International Congress on Sound and Vibration, ICSV 2016, 10 July 2016 through 14 July 2016
Note

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

QC 20161125

Available from: 2016-11-25 Created: 2016-11-03 Last updated: 2019-05-21Bibliographically approved
Pignier, N., O'Reilly, C. J. & Boij, S. (2016). Aeroacoustic study of a submerged air inlet using an IDDES/FW-H approach and sound source modelling through direct numerical beamforming. In: 22nd AIAA/CEAS Aeroacoustics Conference: . 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 >>Aeroacoustic study of a submerged air inlet using an IDDES/FW-H approach and sound source modelling through direct numerical beamforming
2016 (English)In: 22nd AIAA/CEAS Aeroacoustics Conference, American Institute of Aeronautics and Astronautics, 2016Conference paper, Published 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.

Place, publisher, year, edition, pages
American Institute of Aeronautics and Astronautics, 2016
Keywords
Acoustic generators, Aeroacoustics, Air intakes, Flow separation, Linear programming, Mach number, Numerical methods, Transients, Velocity, Deconvolution approach, Detached eddy simulations, Far field spectra, Frequency contents, National advisory committee for aeronautics, Simulation domain, Standard beamforming, Virtual microphone, Beamforming
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-195502 (URN)10.2514/6.2016-2838 (DOI)2-s2.0-84982893795 (Scopus ID)9781624103865 (ISBN)
Conference
22nd AIAA/CEAS Aeroacoustics Conference, 2016, 30 May 2016 through 1 June 2016
Note

QC 20161125

Available from: 2016-11-25 Created: 2016-11-03 Last updated: 2019-03-19Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4103-0129

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