Alexei Poludnenko
School of Mechanical, Aerospace, and Manufacturing Engineering
University of Connecticut (UCONN)

"Supersonic Combustion: From a Detonation Engine to an Exploding Star"

Wednesday, Nov 15, 2023

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Abstract:

Reacting flows are pervasive both in our daily lives on Earth and in the Universe. They power modern society being at the heart of many energy generation and propulsion systems, such as gas turbines, internal combustion and jet engines. At the same time, they also power the Universe through the energy produced in stellar interiors. Despite this ubiquity in Nature, reacting flows still pose a number of fundamental questions concerning their structure and dynamics often exhibiting surprising and unexpected behavior. In recent years, the advent of large-scale direct numerical simulations (DNS) has enabled detailed exploration of the reacting flow dynamics in extreme, previously inaccessible supersonic regimes characterized by high flow speeds, significant compressibility effects, and strong coupling between exothermic reactions and the fast turbulent flow. Such combustion regimes are fundamental to the operation of many modern propulsion applications from scramjets to detonation-based engines. This talk will present an overview of a range of phenomena discovered in recent years in DNS of high-speed reacting flows. These range from intrinsic instabilities of reacting turbulence, which can lead to the onset of catastrophic transitions, e.g., spontaneous detonation formation, to the qualitative changes in the nature of the turbulent cascade in the presence of exothermic reactions, to the fundamental and still largely enigmatic properties of the dynamics of detonations. Finally, challenges presented by these findings will be discussed both in the context of our theoretical understanding of reacting flows, and also in the context of modern modeling paradigms, such as Large Eddy Simulations.