On the collapse of water vapour cavities in a bubble analogue apparatus

Abstract

A mathematical model is derived and used to predict the rate of collapse of a vapour cavity, under an applied pressure gradient in a bubble analogue apparatus. The model assumes incompressible liquid dynamics and treats the loss of heat from the vapour due to condensation as a simple conduction problem through an assumed boundary layer in the liquid. The model has been tested using water at temperatures between 20°C and 85°C. Good agreement was obtained between predictions made from the theory and the experimental observations. The rate controlling mechanism for the rate collapse of a water vapour cavity varies with the bulk temperatures of the liquid. At low temperatures inertial effects are dominant and the rate is governed by the liquid hydrodynamics. At temperature between approximately 55°C and 85°C heat transfer conditions within the water are important. At higher temperature the rate of collapse is not sensitive to heat transfer effects and the vapour in the cavity is compressed adiabatically. Limitations on the use of the model are discussed.