Investigation of rarefaction wave driven Rayleigh-Taylor instability using particle image velocimetry

Experiments are presented in which a diffuse interface between two gases of differing density is accelerated vertically using interaction with a rarefaction wave resulting in the Rayleigh-Taylor instability. Using equal volumetric flow rates of two unequal density gases, a flat interface is formed at the location of small exit holes in the test section. The interface is then given either a 2D or 3D initial perturbation by horizontal or vertical oscillation. A vacuum tank positioned below the test section and separated from it by a diaphragm is evacuated. The rupture of the diaphragm then creates a rarefaction wave resulting in a large (of order 1000 g), non-constant acceleration as it passes over the interface causing the Rayleigh-Taylor instability to develop.

Particle Image Velocimetry is implemented using a laser sheet directed into the test section from above, illuminating the particles seeded in the two gases. The test section is then imaged using three high-speed CMOS cameras and the resulting image sequences are processed to obtain flow velocity fields. The velocity data is then processed to obtain perturbation growth rates along with the development of vorticity and turbulent kinetic energy.