349 / 2019-02-27 11:39:22

Experimental investigation on the evolution of Rayleigh-Taylor instability at tilted interface

tilted interface,Rayleigh-Taylor instability,viscosity effect

全体主题 > Interface Instabilities at Extremes

The evolution of Rayleigh-Taylor instability at titled interface was experimentally investigated in various initial conditions. The titled interface was formed in the hermetic container by gravity which was accelerated by high-pressure gasexpanding on the declined orbits. Once the container was impacted by high-pressure gas, the interface was accelerated downwards to induce Rayleigh-Taylor instability. Thanks to that, the interface deformed and evolved causing fluid mixing at last. By multiple diagnostic technologies such as high-speed photography, shadowgraphyand PIV-PLIF, several initial condition effects were analyzed to reveal the mechanism of interface evolution.
What’s easily understood is that with a higher strength of loading the interface evolves more acutely and the width of mixing area is larger. As a result, the mixing is promoted to develop more adequately. The initial angle of the interface also has a large influence on the late stage of evolution which is adjusted by the position of orbits. The slope of the interface makes the acceleration separated to normal and tangent directions. The tangent acceleration suppresses the development of bubble and spike on the interface. Compared with horizontal interface, the titled interface has a smaller mixing width in the late stage. Moreover, viscosity effect is investigated by comparison of 3 cases with various viscosity. During the evolution the development of small scale structures are restrained by the viscosity. The evolution patterns turn out to be larger scale structures and the boundary of mixing area is more smooth. However, the development mode of mixing area is not changed. Visualized by PIV-PLIF, the velocity near interface in high viscosity case is much smaller than lower viscosity case indicating that the convection caused by instability is weakened by viscosity.