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Analysis of Non-Reflecting Boundary Conditions for Direct Aeroacoustic Simulation with the Lattice Boltzmann Method

  • The Lattice Boltzmann Method is a useful tool to calculate fluid flow and acoustic effects at the same time. Although the acoustic perturbation is much smaller than normal pressure differences in fluid flow, this direct calculation is a great advantage of the Lattice Boltzmann Method (LBM). But each border used in calculation produces a multitude of reflections with the acoustic waves, which lead to anThe Lattice Boltzmann Method is a useful tool to calculate fluid flow and acoustic effects at the same time. Although the acoustic perturbation is much smaller than normal pressure differences in fluid flow, this direct calculation is a great advantage of the Lattice Boltzmann Method (LBM). But each border used in calculation produces a multitude of reflections with the acoustic waves, which lead to an unusable result. Therefore, it is worked on different absorbing techniques. In this thesis three absorbing layer techniques are described, explained and reviewed with different simulations. The absorbing layers are implemented in a basic LBM code in C++, and with this umpteen simulations within a box were performed to compare the different absorbing layers. The Doppler effect and a cylinder flow are also examined to compare the damping efficiencies. The three studied absorbing techniques are the sponge layer, the perfectly matched layer and a force based Term II absorbing layer. The sponge layer is easy to implement but gives worse results than a calculation without any absorbing layer. The perfectly matched layer and a force based absorbing term provide very good results but the perfectly matched layer has problems with instability. The force based absorbing layer represents the best compromise between the additional computation time due the absorbing layer and the achieved damping efficiency.show moreshow less

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Metadaten
Author:Sebastian Sokolov
Place of publication:Offenburg
Year of Publication:2021
Date of first Publication:2021/06/01
Page Number:VI, 80
Language:English
GND Keyword:Lattice Boltzmann Method
Tag:Direct Aeroacoustic Simulation; Non-Reflecting Boundary Conditions
DDC classes:600 Technik, Medizin, angewandte Wissenschaften
Advisor:Andreas Schneider, Alexander Schukmann
Publishing Institution:Hochschule Offenburg
Granting Institution:Hochschule Offenburg
Date of final exam:2021/06/01
Document Type:Master's Thesis
Institutes:Abschlussarbeiten / Master-Studiengänge / MME
Open Access:Zugriffsbeschränkt
Release Date:2021/06/08
Licence (German):License LogoEs gilt das UrhG