Experimental Studies of the Dependence of the Richtmyer- Meshkov Instability on the Atwood number and Dimensionality

In order to verify the prediction of a 2D high Atwood number potential flow model for the evolution of the shock wave induced Richtmyer-Meshkov instability [Phys. Rev. Lett. 74, 534 (1995)], shock-tube experiments were performed with a single-mode perturbation and two competing bubbles as the initial conditions [Phys. Rev. Lett. 80, 1654 (1998)]. The experimental results were compared to theoretical model and to numerical simulation. In the present work the dependence of the Atwood number and the dimensionality on the instability was investigated in a M ≈ 1.2 shock tube apparatus. Two different cases were used to investigate the dependence of the instability on Atwood number - a single-mode perturbation and one consisting of two competing bubbles Different Atwood numbers were achieved by using different gases. The results of those experiments were found to be in very good agreement with the theoretical model prediction as well with a numerical simulation. These results verify the key elements of the Atwood number scaling of the bubble-merger model used for the prediction of the multi-mode bubble and spike front evolution at all Atwood numbers. Both initial cases were used in 3D experiments to investigate the dependence of the instability on the dimensionality. The results reveal the same two key elements of the bubble-merger model to describe the bubble and spike front evolution as in the 2D case except for different scaling constant.