Observation and Measurement of the Growth of the Primary Instabilities of the Richtmyer-Meshkov Instability and Observation of Secondary Instabilities

The following thesis presents an experimental study observing and measuring the change in two of the key features of the Richtmyer-Meshkov (RM) instability in a shock-accelerated, initially cylindrical gas column; that is, the counter-rotating vortex pair and the central spike; and the observation of secondary instabilities within the primary instability. The formation of the instabilities is the result of a standing normal shock wave of air interacting with a cylindrical column of sulfur hexafluoride saturated with acetone. The experimental study is performed at two Mach numbers, 1.7 and 2.1, both with a maximum variation of 10% of either Mach number. The measurements of the size of these features of interest were compared to two external characteristics of the experiment: the actual timing after shock when the instability was measured and the distance downstream of the initial position of the cylindrical gas column. The development of the instability is tracked from the moment of shock impact until transition to turbulence when the flow becomes well-mixed. It was observed that the development of the instabilities with respect to the downstream distance point of observation was weakly correlated to the experimental Mach number. In contrast, a stronger correlation between the downstream distance and the feature size was evident. This behavior was previously observed for the counter-rotating vortex pairs, but it is a new observation for the growth of the spike that forms due to shock focusing.National Nuclear Security AgencyMechanical EngineeringMastersUniversity of New Mexico. Dept. of Mechanical EngineeringVorobieff, PeterTruman, C. RandallPetsev, Dimite