Weekly Seminar: Fall 2013
Speaker: Dr. Devesh Ranjan (Texas A&M University)
Title: "Fluid Instabilities and Mixing in Extreme Conditions"
Date: Friday, October 25, 2013
Time: 11:00 a.m.
Location: Gilman Hall 50 (Marjorie M. Fisher Hall)
Mixing is central to several important phenomena in nature and engineering. Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) driven wrinkles at the interface of materials lie at the heart of an overarching science for material mixing that stretches from oil trapping salt domes, that develop over tens of millions of years, to degradation of Inertial Confinement Fusion (ICF) capsule performance in 10 -12 ns. Everyday phenomena include mixing of milk into coffee, and emptying of water from a glass. Technological and environmental applications include: drop disintegration in engine fuel sprays, enhanced heat transfer in tubes, plasma instabilities, material component mixing in the pharmaceutical industry, and buoyancy driven flows in the oceans and atmosphere. RT and RM are insidious instabilities that start with exponential growth of small scale perturbations, and end in a fully turbulent mixing process. It is this scale range and chaotic nature that challenges our experimental capabilities and physical understanding. But, the timely need to understand, predict, control, and utilize is because RT/RM mixing lies at the heart of national security priorities such as energy, threat reduction, and NNSA interests. Should the relationship between initial conditions and mixing be determined, then, in principle, the level of mixing could be controlled through the setting of specific conditions. In this seminar, I will describe the results from recent laboratory experiments for studying the shock-accelerated inclined interface problem and coupled RT & Kelvin-Helmholtz (KH) environment. Specifically, the effect of adding shear to a gravitationally unstable configuration will be discussed in detail. In these experiments, the flow visualizations are obtained using planar laser diagnostics (Mie-scattering and Planar laser-induced fluorescence). Simultaneous hot-wire and cold wire anemometry was implemented to obtain point-wise instantaneous velocities and density in the evolving flow field.
Dr. Devesh Ranjan is an assistant professor and Morris E. Foster Faculty Fellow in the Department of Mechanical Engineering at Texas A&M University. He received his bachelor's degree from the National Institute of Technology, Trichy (India), in 2003, and master's and Ph.D. degrees from the University of Wisconsin in 2005 and 2007 respectively, all in mechanical engineering. During 2008, he was a Director’s Postdoctoral Fellow at Los Alamos National Laboratory. His research interests are in the area of turbulence and mixing at extreme conditions, analysis of shock-driven flows, and design of thermal systems. In 2013 he was named a recipient of the Young Investigator's Research Program Award (YIP) by the Air Force Office of Scientific Research and the National Science Foundation CAREER Award.