Dynamics of a Spherical Vapor/Gas Bubble in Varying Pressure Fields

Abstract

A mathematical model is developed to simulate the radial motion of cavitation bubbles. The heat and mass transports including phase change are formulated precisely. In order to reduce the computational cost without loss of the important thermo-fluid phenomena, two simplifications are employed: time-dependent bubble radius is described using the Rayleigh-Plesset equation; the pressure in the bubble is assumed to be uniform in space. For validation of the model, the transient radial motion of an air bubble in water is observed experimentally. A shock tube is used to make the sudden pressure reduction from atmospheric to below the saturated vapor pressure. The bubble radius is measured by high-speed photography, in which an interferomtric laser imaging technique is used for accurate determination of the initial bubble radius. The radial motion is successfully predicted by using this model. The temperature reduction at the bubble wall is a predominant factor on the bubble growth rate under superheated conditions, even if the liquid temperature is close to room temperature. The numerical result indicates that the growth rate is very sensitive to initial bubble radius, ambient pressure, and liquid temperature.