Analysis of Acoustic Cavitation Phenomenon Using Acoustic Emission Technique and Numerical Modelling of the Phenomenon

Abstract

As an initial step to develop a new quantitative cavitation erosion model test method using acoustic emission (AE) technique, this thesis aimed to estimate an AE threshold to cause soft paint coat damage by an ultrasonic cavitation apparatus experimentally and to construct a numerical model of acoustic cavitation from such a device to get more insight to the possible physical mechanisms to cause such damage. Especially, in conjunction with the numerical model, a stability problem with a compressible multiphase flow solver using a barotropic relation is addressed. A series of experiments to estimate the AE threshold were carried out using a sonotrode (tip diameter: 16 mm) with the nominal working frequency of 20 kHz and maximum power output of 1 kW mimicking the soft paint tests. AE signals from acoustic cavitation were measured and analysed. To support the experiment and to get more insight to the involved physics, numerical studies were carried out using an open source CFD software package suite, OpenFOAM (v.3.0.1) in three phases. To analyse acoustic cavitation oscillation characteristics by AE, an FFT technique was used. The measured AE signal magnitudes were found to be consistent against various impact loadings. In modelling acoustic cavitation from ASTM G-32 type devices based on a compressible multiphase flow solver using a barotropic cavitation model, it was found to be critical for the stability and the physical soundness of the solution, to ensure boundedness of the mass convection term and to satisfy the CFL number close to one. This research will contribute to future development of a new quantitative model erosion test method based on AE technique.

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Identifiers

ORCID for Byoung Guk Kim: orcid.org/0000-0002-7410-8220

ORCID for Stephen Turnock: orcid.org/0000-0001-6288-0400

ORCID for Philip Wilson: orcid.org/0000-0002-6939-682X

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