Density dependence of Rayleigh-Taylor and Richtmyer-Meshkov mixing fronts

We propose a pair of ordinary differential equations to describe the motion of the two edges of a Rayleigh-Taylor (RT) or Richtmyer-Meshkov (RM) mixin g zone. These model equations give a simple physics - based description of the RT and RM mixing rates. The equations are in agreement with all availab le experiments, including the recent LEM RT and RM experiments for spikes a s well as bubbles. In particular, the model equations predict that the scal ing constants alpha(s) --> 0.5 and theta --> 1 as the Atwood number A --> 1 . (C) 2000 Elsevier Science B.V. All rights reserved.