Aeroacoustic simulation of the edge tone

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Supervisor:
Dr. Rucz Péter
Department of Networked Systems and Services

The edge tone is an aeroacoustic phenomenon created by a planar free jet impinging a sharp edge-shaped obstacle. The edge destabilizes the flow, and the evolving pressure fluctuations work as an acoustic dipole. This sound provides the excitation for various wind instruments, such as the flute, or the flue pipes of an organ. This phenomenon is significant in a number of other applications as well, for example the traffic noise caused by pantographs of high-speed electric trains. The purpose of this thesis is the development of an aeroacoustic model which is capable of the realistic reproduction of the edge tone.

During the examination a two-dimensional numerical model was created based on a certain edge tone arrangement found in the corresponding literature. The simulation was designed as a so-called hybrid method, that consists of a fluid dynamic and an acoustic system. In the fluid dynamic simulation I used the OpenFOAM software package to solve the incompressible set of Navier - Stokes equations by means of the finite volume method. After that, I calculated the acoustic sources using Lighthill's analogy, and then I utilized finite element method extended by infinite elements in order to simulate the wave propagation. I performed the aeroacoustic simulations in time-domain, using a self-developed Matlab code.

To validate the results, I examined the sound field of a co-rotating vortex pair, in which case the analytic solution is known. Finally, I compared the results of the calculations with measurement data from the literature. This paper proves that the implemented hybrid model is capable of calculating the characteristics of the edge tone.

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