Modelling of the cavitation bubbles dynamics

Merim Elezović

Master's thesis

Abstract:

The goal of this study is to apply a numerical model for cavitation bubble dynamics that is based on the existing Rayleigh-Plesset equation (RPE). Physical background and derivation of the RPE are given, as well as the basic phenomena associated with cavitation, such as nucleation, shockwaves, and microjets. Several adverse effects of cavitation are discussed, in addition to domains in which cavitation was found to be useful, and the classification of cavitation. Since RPE is a second order ordinary differential equation (ODE), it had to be converted into a system of two first order ODEs before being solved numerically. Runge-Kutta numerical method of fourth order was selected as the most suitable method for solving a system of ODEs, and then applied on the relations in the RPE. For the model application, computational power of Microsoft Excel was determined to be sufficient to handle all the necessary calculations. Furthermore, the impact of changes in different criteria, initial conditions and fluid parameters is studied, such as: bubble initial radius, pressure amplitude, surface tension, and liquid viscosity. Model is then verified based on existing numerical results. Model is then validated towards two types of experiments - laser-induced cavitation bubble, and spark-generated bubble. Finally, applicability of the model for cavitation erosion prediction is briefly discussed.

Abstract:

The goal of this study is to apply a numerical model for cavitation bubble dynamics that is based on the existing Rayleigh-Plesset equation (RPE). Physical background and derivation of the RPE are given, as well as the basic phenomena associated with cavitation, such as nucleation, shockwaves, and microjets. Several adverse effects of cavitation are discussed, in addition to domains in which cavitation was found to be useful, and the classification of cavitation. Since RPE is a second order ordinary differential equation (ODE), it had to be converted into a system of two first order ODEs before being solved numerically. Runge-Kutta numerical method of fourth order was selected as the most suitable method for solving a system of ODEs, and then applied on the relations in the RPE. For the model application, computational power of Microsoft Excel was determined to be sufficient to handle all the necessary calculations. Furthermore, the impact of changes in different criteria, initial conditions and fluid parameters is studied, such as: bubble initial radius, pressure amplitude, surface tension, and liquid viscosity. Model is then verified based on existing numerical results. Model is then validated towards two types of experiments - laser-induced cavitation bubble, and spark-generated bubble. Finally, applicability of the model for cavitation erosion prediction is briefly discussed.

Keywords

cavitation, bubble dynamics, Rayleigh-Plesset equation, laser-induced bubble, spark-generated bubble

Language used: English

Date on which the thesis was submitted / produced: 7. 6. 2021

Thesis defence

• Supervisor: Ing. Miloš Müller, Ph.D.

Technical University of Liberec

Faculty of Mechanical Engineering

Master programme / field:
Mechanical Engineering / Machines and Equipment Design