NUMERICAL PREDICTION OF SIZE DISTRIBUTION OF MICROBUBBLES IN WATER WITH MASS TRANSFER

Abstract

It has been reported that the diameter and the number density of microbubbles would change in time due to mass transfer between bubbles and surrounding liquid. However, few numerical studies have been conducted on the time evolution of diameters of single microbubbles or groups of microbubbles due to mass transfer. Numerical simulations based on the Rayleigh-Plesset equation were therefore carried out to investigate the time evolution of bubble diameter and the mass transfer of dissolved gas between bubbles and water in microbubble flow in a duct. As a result, the following conclusions were obtained: (1) the present numerical method can accurately predict the growth and shrinkage of a single microbubble. (2) Microbubbles in a flow usually have size distribution, in which bubbles larger and smaller than the equilibrium diameter become larger and smaller in time, respectively. Thus, the size distribution changes in time. (3) The proposed numerical method can reasonably predict time evolutions of bubble size distributions, void fractions, and concentrations of dissolved gas, provided that a reliable initial condition is available.