Environmental effects on bubble dynamics: Numerical simulation and applications

The study of bubble dynamics is important in a wide range of applications. However, the behavior of a gas bubble is strongly affected by the environment around the bubble, and therefore becomes more complicated than simplified models predict. Through numerical simulation, this dissertation investigates the effects of several environmental factors on the bubble dynamics. These factors are: the gas diffusion between the bubble and the ambient liquid; the high viscosity of the host liquid; a rigid or a free surface boundary near the bubble; the collapse of a neighboring bubble.;By using the one-dimensional Gilmore model for bubble dynamics and the Eller-Flynn theory for gas diffusion between an oscillating bubble and ambient liquid, the effect of gas diffusion is investigated. The results show that the gas diffusion can cause a gas bubble either to dissolve or grow, depending on the competition between the passive diffusion and rectified diffusion. It is also shown how gas diffusion and its effects depend on the bubble's size as well as the frequency of the applied acoustic waves.;The effect of the viscosity of the host liquid on the threshold of inertial cavitation is also investigated by using the Gilmore model. It is found that the threshold for inertial cavitation is not always well defined and the widely-used criterion for the inertial cavitation threshold Rmax/R0≥2 is not appropriate for highly viscous host liquids. An alternative criterion is then proposed.;A two-dimensional hydrodynamics code based on the finite volume method is updated and used to investigate the effects of a rigid or a free surface boundary near the bubble. The results show the non-spherical collapse and jet formation of a bubble when it collapses near a boundary. The mechanism of jet formation is analyzed by displaying the details of the pressure and velocity fields and the pathlines of the gas-liquid interface. The results are compared with reported experimental observations and numerical calculations obtained using the boundary integral method. They show good agreement with each other.;The problem of two bubbles sequentially impacted by a weak shock is also studied by using the 2-D code. Generally, the collapse of the first bubble has a small effect on the second bubble, mainly because the amplitudes of the radiated pressure waves decay rapidly with distance.