Event
Fluid Dynamics Reviews Seminar Series: S. Balachandar, University of Maryland
Friday, October 16, 2015
10:00 a.m.
DeWalt Seminar Room, 2164 Martin Hall
Johan Larssonn
jola@umd.edu
http://www.enme.umd.edu/events/fluid-dynamics-review-seminars
THE BURGERS PROGRAM for FLUID DYNAMICS and THE MINTA MARTIN FUND present
THE FLUID DYNAMICS REVIEWS SEMINAR SERIES
Speaker: S. Balachandar
Director, Institute for Computational Engineering
Director, DOE PSAAP Center for Compressible Multiphase Turbulence
William F. Powers Professor of Mechanical & Aerospace Engineering
University of Florida
MULTISCALE MODELING OF COMPRESSIBLE MULTIPHASE FLOWS -SHOCK-PARTICLE INTERACTION TO EXPLOSIVE DISPERSAL
Abstract: We will look at the problem of explosive dispersal of particles and ask the question what will it 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 mostly cover a series of recent rigorous theoretical results for (a) equation of motion for a rigid particle in a unsteady compressible ambient flow (compressible BBO equation), (b) Generalized Faxen theorem for spatially varying compressible ambient flows (c) extension to bubbles and droplets, (d) second order acoustic forces on particle/bubble/droplet, (e) application to shock-particle interaction.
The talk will then a present a rational approach that builds upon these rigorous theoretical results to develop advanced momentum and energy coupling models in a systematic way. This leads to 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.
