Experimental Investigation of Statistically Steady Rayleigh-Taylor Mixing at High Atwood Numbers

In the present work, a novel gas channel experiment was used to study the non-equilibrium development of high Atwood number Rayleigh-Taylor mixing. Two gas streams, one containing air and the other containing a Helium-Air mixture, flow parallel to each other separated by a thin splitter plate. The streams meet at the end of the splitter plate leading to the formation of an unstable interface and initiation of buoyancy driven mixing. This buoyancy driven mixing experiment allows for long data collection times, short transients and was statistically steady. The facility was capable of large Atwood number studies (At ∼ 0.75). Here, we describe recent work to measure the self similar evolution of mixing at large density differences (At ∼ 0.1). Diagnostics include a constant temperature Hot Wire anemometer, and high resolution thermocouple measurements. The Hot Wire probe gives velocity statistics of the mixing layer. A multi-position single-wire technique was used to measure the velocity fluctuations in three mutually perpendicular directions. Analysis of the measured data was used to explain the structure of mixing as it develops to a self-similar regime in this flow.