Experiments on the Richtmyer-Meshkov Instability with an Imposed, Random Initial Perturbation

Experimental Set-Up

Membraneless Richtmyer-Meshkov instability experiments have previously been carried out in a vertical shock tube using a single-mode two- and three-dimensional initial perturbations [1], [2]. The present study utilizes the apparatus and experimental techniques of these previous investigations modified to allow the generation of a random three-dimensional initial perturbation.

A 5m long vertical shock tube with a 10.2cm diameter round driver, and a 8.9cm square test section is used for this study. The light gas (air) enters the tube at the top of the driven section immediately below the diaphragm, and the heavy gas (SF₆) enters at the bottom of the test section. The gases exit the shock tube through a series of small holes in the test section walls, leaving behind a flat, diffuse interface. In the previous studies the initial perturbation was generated by periodically oscillating the square shock tube, laterally, to produce a nearly single-mode two-dimensional standing wave. More recently [3] we have found that we can produce similar single mode three-dimensional standing waves by oscillating the gas column within the shock tube vertically using the periodic motion of a piston mounted at the bottom of the test section. The work presented here is a continuation of that work in which the frequency of this motion is increased producing a more random, short wavelength pattern.