Aeroacoustic modeling of a whistle

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

A whistle is a simple aerophone, which produces sound as a result of hydrodynamic and acoustic interactions. Since the acoustic field strongly affects the hydrodynamic behaviour during this process, the two systems are strongly coupled.

This thesis examines the operation of a whistle from both a hydrodynamic and an acoustic aspect, thus, the theoretical background of the problem is thoroughly reviewed first. Starting from the principles of mass and momentum conservation the Navier-Stokes equations are derived in a step-by-step manner. These are the foundations of the CFD (Computational Fluid dynamics) simulation. Looking at the same principles from an acoustic point of view we obtain the Helmholtz equation, on which the acoustical simulation is based. Comparing these two approaches we frame the possible directions of the simulations.

Both the CFD and acoustical simulations are implemented by means of numeric methods. We follow through every phase of the making of a three-dimensional whistle model starting from a simple geometry. An important goal of this thesis is that we aim to assemble these simulations by exclusively using free or open source software.

We also focus on combining the operation of these programs and overcoming the arising compatibility issues.

During the acoustic simulation the two- and three-dimensional models are investigated in the frequency domain using a steady-state excitation. Then both models are examined in a hydrodynamic framework. Finally, we attempt to run a compressible simulation that combines the nature of both the acoustical and hydrodynamical models.

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