Woodruff School of Mechanical Engineering


Compressible Multiphase Flows from Shock-particle interaction to explosive particle dispersal.


Dr. Sivaramakrishnan Balachandar


University of Florida


Tuesday, February 6, 2018 at 11:00:00 AM


MRDC Building, Room 4211


Dr. Devesh Ranjan


We will look at the problem of explosive dispersal of particles and ask the question what it will take to perform predictive simulations of this complex physics from first principles. Compressible flow resulting from an explosive release of energy is a classic problem. During and after the Second World War, due to interest in better understanding nuclear explosions, this problem attracted some of the best scientists of that time - G.I. Taylor, von Neumann, Hans Bethe, and L.I. Sedov. The presence of particles, as in a hybrid multiphase explosive or dispersal of fragments greatly complicates the problem. The interaction of between the gas and the particulate field is significantly complicated due to (a) the highly unsteady nature of the problem, (b) interaction of compressible flow features such as shocks and contacts with the particles, (c) high Reynolds number, (d) compressibility effects of high Mach number, (e) particle-particle interaction at large volume fractions, (f) random particle size, shape and distribution, and (g) instability and flow turbulence. Despite these complexities, current approaches, due to lack of fundamental understanding, are forced to rely upon standard drag and heat transfer relations that are developed for much simpler conditions. The talk will cover recent results on (a) Development of the Generalized Faxen theorem for modeling of force on a particle subjected to a spatially varying compressible flow (b) application to shock-particle and expansion-fan-particle interaction, (c) Extension of the theory to particle-particle interaction effects in shock-particle-cloud interaction, and (d) Instability analysis of explosively dispersing particle clouds. We will discuss a hierarchical approach that spans from the microscale (order of few particles), to mesoscale (order of millions of particles), to macro or system scale of practical interest. A key aspect of this modeling and simulation approach is rigorous validation of the coupling model at every stage of the hierarchy against high quality experimental results.


S. (Bala) Balachandar got his undergraduate degree in Mechanical Engineering at the Indian Institute of Technology, Madras in 1983 and his MS and PhD in Applied Mathematics and Engineering at Brown University in 1985 and 1989. From 1990 to 2005 he was at the University of Illinois, Urbana-Champaign, in the Department of Theoretical and Applied Mechanics. From 2005 to 2011 he served as the Chairman of the Department of Mechanical and Aerospace Engineering at the University of Florida. Currently he is a distinguished professor at the University of Florida. He is the William F. Powers Professor of Mechanical & Aerospace Engineering and the Director of College of Engineering Institute for Computational Engineering. Bala received the Francois Naftali Frenkiel Award from American Physical Society (APS) Division of Fluid Dynamics (DFD) in 1996 and the Arnold O. Beckman Award and the University Scholar Award from University of Illinois. He is Fellow of ASME and the American Physical Society Division of Fluid Dynamics. He received the Freeman Award from ASME in 2017. He is currently an editor-in-chief of the International Journal of Multiphase Flow and the handling editor for the Theoretical and Computational Fluid Dynamics.


Refreshments will be served.