The Beauty of Turbulence and Transitions in Reactive Flows
Abstract
This is an informal (and hopefully interactive) seminar during which the speaker will describe some of the work she has been doing during the past five years at the University of Maryland. She will first summarize the various topics and their applications, and then, as time allows, pick one or two for deeper discussion.
In particular, the speaker will emphasize two applications of what she believes are the most complex and difficult problems in fluid dynamics: transitions among what seem to be relatively stable states. When such systems also involve energetic interactions, as instigated by nuclear or chemical reactions, or some other of local energy deposition, the results can be dramatic and unexpected. Such reactive-flow transitions are critical elements in the working of 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. Applications here include, for example, hypersonic propulsion or safety issues in large-scale fuel explosions. For this type of turbulent reactive flow, numerical simulations coupled to available experiments have played an important role in understanding the mechanisms, structure, and dynamics.
The second regime is a purely subsonic flow that involves a transition from a fire whirl to a small, soot-free, totally blue flame, the blue whirl, which completely consumes liquid hydrocarbon fuels, yet producing no soot and minimal pollutants. The speaker and her research group observed transition to a blue whirl occurs when the turbulence in the fire whirl reaches a level of intensity that allows 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, extremely clean flame that will, literally, burn everything to completion.
About the speaker
Prof. Elaine Oran received her MPhil in Physics and PhD in Engineering and Applied Science at Yale University. She joined the faculty of the University of Maryland in 2013 as Glenn L. Martin Institute Professor of Engineering. 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.
