The Beauty of Turbulence and Transitions in Reactive Flows

Abstract

Some of the most interesting, complex, and difficult problems in fluid dynamics involve transitions among what seem to be relatively stable states of a system. When these systems also involve locally evolving energy sources, such as those as caused by nuclear or chemical reactions, the results can be dramatic and unexpected. This type of reactive flow is critical to systems ranging from engines for propulsion, to accidental fuel explosions, to explosions of thermonuclear supernova, and arguably to the primal explosion that created the universe.

Two very different regimes of chemically reacting flows will be described in this presentation. The first involves high-speed flows with turbulent flames and possible transition to detonation. Large-scale numerical simulations coupled with laboratory and field experiments have played an important role in understanding the mechanisms, structure, and dynamics of these flows. The second regime is a purely subsonic flow that involves a transition from a dangerous fire whirl to a small, soot-free, totally blue flame, the blue whirl. The transition to a blue whirl occurs when the turbulence in the fire whirl reaches a level of intensity that enables vortex breakdown, and it appears as a transition from turbulence. The blue whirl is “new territory,’’ and experiments, simulations, and theory are all trying to understand the properties and limits of this strange, intensely blue, soot-free flame.

About the speaker

Prof. Elaine S. Oran received her MPhil in Physics and PhD in Engineering and Applied Science at Yale University. She joined the University of Maryland in 2013 as Glenn L. Martin Institute Professor of Engineering, and has been TEES Eminent Professor and subsequently O'Donnell Foundation Chair VI of the Department of Aerospace Engineering at Texas A&M University since May 2019. She is also an Adjunct Professor of Aerospace Engineering at the University of Michigan and a Visiting Professor at the University of Leeds. Before joining the University of Maryland, she was the Senior Scientist for Reactive Flow Physics at the US Naval Research Laboratory and was responsible for carrying out theoretical and computational research on the fluid and molecular properties of complex dynamic systems.

Prof. Oran's recent research interests include combustion and propulsion, rarefied gases and microfluidics, fluid turbulence, materials engineering, high-performance computing and parallel architectures, computational science and numerical analysis, biophysical fluid dynamics, wave equations, and astrophysical phenomena such as supernova explosions and jets. She is author of over 300 refereed journal articles as well as many conference papers and presentations. She is also the co-author of the book Numerical Simulation of Reactive Flow.

Prof. Oran is a Member of the US National Academy of Engineering, an Honorary Fellow of the American Institute of Aeronautics and Astronautics (AIAA), and a Fellow of both the American Physical Society (APS) and the Society of Industrial and Applied Mathematics. She was awarded the Propellants and Combustion Award from AIAA in 2008 and the Fluid Dynamics Prize from APS in 2013.

For Attendees' Attention

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