Mechanical Engineering Seminar
Tuesday, October 22, 2019
10:15 a.m., 3540 Engineering Building
Refreshments Served at 10:00 a.m.
Variable-Density Mixing and Turbulence at Extreme Conditions
Dr. Devesh Ranjan
Associate Chair for Research
J. Erskine Love, Jr. Associate Professor
Woodruff School of Mechanical Engineering
Georgia Institute of Technology
Mixing is central to several important phenomena in nature and engineering. Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) driven perturbations 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 s. RT and RM are insidious instabilities that start with exponential growth (power-law function of time for RM) of small-scale perturbations, and end in a fully turbulent mixing process. During the first half of the talk, I will present results from our multi-layer gas tunnel facility (convective setup) and shock-tube, which has been used to acquire simultaneous density and velocity turbulent statistics for RT and RM Instability at high density contrast. Density, velocity, and density–velocity cross-statistics are calculated using ensemble averaging to investigate the effects of additional modes on the mixing and turbulence quantities. During the second half, I will describe the results from studies of freely expanding flames in a unique small-scale convective facility for different free-stream initial conditions, characterized by Taylor-Reynolds numbers in the range of 150-400. The isotropic, decaying turbulence is generated by an active vane grid. Adding natural gas far upstream, the premixed flow is ignited using Laser Induced Breakdown (LIB) ignition. The evolution of the resulting spherically expanding flames is investigated using qualitative OH-Planar Laser Induced Fluorescence (PLIF). Reliable computation of the flame surface density and turbulent flame brush thickness is enabled by the large number of ensembles that can be collected in this type of facility. Trends of these instantaneous statistical quantities are presented and used to further assess the results of time-dependent mean quantities.
Dr. Devesh Ranjan is an Associate Chair for Research and J. Erskine Love Jr. Associate Professor in the Woodruff School of Mechanical Engineering at Georgia Institute of Technology. He was previously a director's research fellow at Los Alamos National Laboratory (2008) and Morris E Foster Assistant Professor in the Mechanical Engineering department at Texas A&M University (2009-2014). He earned a bachelor's degree from the NIT-Trichy (India) in 2003, and master's and Ph.D. degrees from the UW-Madison in 2005 and 2007 respectively, all in mechanical engineering. His research program focuses on the shock-driven mixing and combustion, the physics of hydrodynamic instabilities, and advanced power conversion cycles. He is a recipient of National Science Foundation CAREER Award, US AFOSR Young Investigator Award and the DOE-Early Career Award. He was an invited participant in the 2016 National Academy of Engineering’s US Frontiers of Engineering Symposium and 2019 Global Grand Challenges Summit. He is currently an Associate Editor of ASME Journal of Fluids Engineering and serves on the Editorial board of Shock Waves (Publisher-Springer & Verlag).
Persons with disabilities have the right to request and receive reasonable accommodation. Please call the Department of Mechanical Engineering at 517-355-5131 at least one day prior to the seminar; requests received after this date will be met when possible.