Richtmyer-Meshkov instability (i.e. the instability of an interface separating two differing density fluids which is impulsively accelerated by a normal-traveling, parallel shock wave) is a very fundamental fluid instability which is of importance to the fields of astrophysics, inertial fusion and combustion. However, the difficulty in generating a well defined interface between two gases has forced previous researchers to use thin membranes to initially separate the gases in shock tube experiments. The presence of the membrane impedes the visualization of the interface. Furthermore, it is the most likely reason why these experiments have not been able to produce growth rate measurements that are comparable to those predicted by the existing linear stability theory.

Two novel experiments will be described in this talk which improve upon previous experimental studies of Richtmyer-Meshkov instability in that very well defined initial interfaces are obtained without the use of a membrane. The first is a shock tube experiment in which a well controlled interface is generated by flowing a light and a heavy gas from opposite ends of a vertical shock tube. The second is an incompressible experiment in which an impulsive acceleration is given to a system of two liquids by bouncing it off of a fixed spring. In both experiments a sinusoidal initial shape is given to the interfaces by gently shaking the experimental apparatus in the horizontal direction to produce standing waves. Both experiments provide particularly well visualized images of the instability far into the nonlinear regime and yield initial growth rate measurements that are in very good agreement with linear stability theory.