A NUMERICAL STUDY OF BUBBLE INTERACTIONS IN RAYLEIGH-TAYLOR INSTABILITY FOR COMPRESSIBLE FLUIDS

The late nonlinear and chaotic stage of Rayleigh-Taylor instability is characterized by the evolution of bubbles of the light fluid and spikes of the heavy fluid, each penetrating into the other phase. This paper is focused on the numerical study of bubble interactions and their effect on the statistical behavior and evolution of the bubble envelope. Compressible fluids described by the two-fluid Euler equations are considered and the front tracking method for numerical simulation of these equations is used. Two major phenomena are studied. One is the dynamics of the bubbles in a chaotic environment and the interaction among neighboring bubbles. Another one is the acceleration of the overall bubble envelope, which is a statistical consequence of the interactions of bubbles. The main result is a consistent analysis, at least in the approximately incompressible case of these two phenomena. The consistency encompasses the analysis of experiments, numerical simulation, simple theoretical models, and variation of parameters. Numerical simulation results that are in quantitative agreement with laboratory experiment for one-and-one-half ( 11/2) generations of bubble merger are presented. To the authors' knowledge, computations of this accuracy have not previously been obtained. © 1990 American Institute of Physics.