MAE Seminar: Numerical Simulations of Complex Multiphase Flows - Opportunities and Challenges

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Gretar Tryggvason, Ph.D.

Charles A. Miller Jr. Distinguished Professor; Head
Department of Mechanical Engineering
Johns Hopkins University


Abstract: Multiphase flows are critical for industrial and natural processes, including the vapor generation in power plants; combustion of liquid fuels; processing of chemicals in bubble columns, rain and heat; and mass exchange between the oceans and the atmosphere. Predicting their behavior is therefore of utmost interest. Direct numerical simulations, where the governing continuum equations are solved accurately for systems that are large enough so that meaningful statistical quantities can be computed, are rapidly becoming routine, at least for systems where the physics is simple enough, such as disperse flows of bubbles and drops. Those simulations yield enormous amounts of data that, in addition to providing physical insights, open up new opportunities for the development of lower order, or coarser, models that describe the average or large-scale behavior. We discuss efforts to do so, including the use of machine learning to construct closure models for bubbly flows. In addition, success with relatively simple systems calls for simulations of more complex problems. Multiphase flows often produce features such as thin films, filaments and drops that are much smaller than the dominant flow scales and are well described by analytical or semi-analytical models. We discuss efforts to combine semi-analytical models for thin films using classical thin film theory and modeling of mass transfer in high Schmidt number bubbly flows using boundary layer approximations, in combination with fully resolved numerical simulations of the rest of the flow.

Bio: Gretar Tryggvason is the Charles A. Miller, Jr. Distinguished Professor at the Johns Hopkins University and the head of the Department of Mechanical Engineering. He received his Ph.D. from Brown University in 1985 and was on the faculty of the University of Michigan in Ann Arbor until 2000, when he moved to Worcester Polytechnic Institute as the head of the Department of Mechanical Engineering. Between 2010 and 2017, he was the Viola D. Hank professor at the University of Notre Dame and the chair of the Department of Aerospace and Mechanical Engineering. Tryggvason is well known for his contributions to computational fluid dynamics, particularly the development of methods for computations of multiphase flows and for pioneering direct numerical simulations of such flows. He served as the editor-in-chief of the Journal of Computational Physics 2002-2015; is a fellow of APS, ASME and AAAS; and the recipient of several awards, including the 2012 ASME Fluids Engineering Award and the 2019 ASTFE Award.