Time filter

Source Type

Kierkegaard A.,MWL Marcus Wallenberg Laboratory for Sound and Vibration Research | Kierkegaard A.,Linne Flow Center | Kierkegaard A.,KTH Royal Institute of Technology | Boij S.,MWL Marcus Wallenberg Laboratory for Sound and Vibration Research | And 5 more authors.
Journal of Sound and Vibration | Year: 2012

The scattering of acoustic plane waves at a sudden area expansion in a flow duct is simulated using the linearized NavierStokes equations. The aim is to validate the numerical methodology for the flow duct area expansion, and to investigate the influence of the downstream mean flow on the acoustic scattering properties. A comparison of results from numerical simulations, analytical theory and experiments is presented. It is shown that the results for the acoustic scattering obtained by the different methods gives excellent agreement. For the end correction, the numerical approach is found superior to the analytical model at frequencies where coupling of acoustic and hydrodynamic waves is significant. A study with two additional flow profiles, representing a non-expanding jet with an infinitely thin shear layer, and an immediate expansion, shows that a realistic jet is needed to accurately capture the acoustichydrodynamic interaction. A study with several different artificial jet expansions concluded that the acoustic scattering is not significantly dependent on the mean flow profile below the area expansion. The constructed flow profiles give reasonable results although the reflection and transmission coefficients are underestimated, and this deviation seems to be rather independent of frequency for the parameter regime studied. The prediction of the end correction for the constructed mean flow profiles deviates significantly from that for the realistic profile in a Strouhal number regime representing strong coupling between acoustic and hydrodynamic waves. It is concluded that the constructed flow profiles lack the ability to predict the loss of energy to hydrodynamic waves, and that this effect increases with increasing Mach number. © 2011 Elsevier Ltd. All rights reserved.


Kierkegaard A.,MWL Marcus Wallenberg Laboratory for Sound and Vibration Research | Kierkegaard A.,Linne Center | Kierkegaard A.,KTH Royal Institute of Technology | Allam S.,MWL Marcus Wallenberg Laboratory for Sound and Vibration Research | And 7 more authors.
Journal of Sound and Vibration | Year: 2012

This paper demonstrates a linear aeroacoustic simulation methodology to predict the whistling of an orifice plate in a flow duct. The methodology is based on a linearized NavierStokes solver in the frequency domain with the mean flow field taken from a Reynolds-Averaged NavierStokes (RANS) solution. The whistling potentiality is investigated via an acoustic energy balance for the in-duct element and good agreement with experimental data is shown. A Nyquist stability criterion based on the simulation data was applied to predict whistling of the orifice when placed in a finite sized duct and experiments were carried out to validate the predictions. The results indicate that although whistling is a nonlinear phenomena caused by an acoustic-flow instability feed-back loop, the linearized NavierStokes equations can be used to predict both whistling potentiality and a duct systems ability to whistle or not. © 2011 Elsevier Ltd. All rights reserved.


Na W.,KTH Royal Institute of Technology | Na W.,Linne Center | Na W.,2 Vehicle Design Center | Efraimsson G.,KTH Royal Institute of Technology | And 6 more authors.
22nd International Congress on Sound and Vibration, ICSV 2015 | Year: 2015

The paper presents a numerical methodology for the prediction of the thermoacoustic instabilities with the effects of the mean-flow as well as the viscosity. As an academic standard test case, the configuration within the flame sheet located in the middle of the duct is investigated. First, the ducted flame numerical reference case is solved by the inhomogeneous Helmholtz equations in combination of the n - τ flame model assuming that the flow is at rest. Then, we derive the linearized Navier-Stokes equations (LNSE) in frequency domain in combination of the flame model. The unsteady effect of the flame is modeled by the n - τ flame model in harmonic form, which is essentially a 1D formulation relating the rate of heat release and the acoustic velocity at the reference point.

Loading MWL Marcus Wallenberg Laboratory for Sound and Vibration Research collaborators
Loading MWL Marcus Wallenberg Laboratory for Sound and Vibration Research collaborators