Details of Research Outputs

The gravitational acceleration of a heavier fluid into a lighter fluid causes unstable modes to grow in the interface between the two fluids and leads to their eventual chaotic mixing. This phenomena is known as the Rayleigh-Taylor instability. We discuss the development and validation of a model for the long term dynamics of the mixing boundary layer. The model uses a simplied description of the dynamics of the bubbles of lighter fluid rising in the heavier fluid. Validation of the model is achieved by comparison with experiments and full scale two dimensional simulations of the mixing process. 

We also discuss the production of anomalous waves during the interaction of shock waves with fluid interfaces. The focus here is on the case when the shock passes from a medium of high to low acoustic impedance. Curvature of either of the interacting waves causes the diffraction patterns produced during the collision to bifurcate from locally self-similar pseudo-stationary configurations to unsteady anomalous reflections. This process is analogous to the transition from a regular to a Mach reflection where the reflected wave is a rarefaction instead of a shock. These bifurcations are incorporated into a front tracking code that gives an accurate description of the wave interactions. Numerical results for two illustrative cases are described; a planar shock passing over a bubble, and an expanding shock impacting a planar contact.