Supersonic Reacting Flows

Reacting flows are pervasive both in our daily lives on Earth and in the Universe. Such flows are fundamental to systems ranging from astrophysical Type Ia supernovae explosions to novel propulsion applications such as scramjets or detonation-based engines. Despite this ubiquity in Nature, turbulent reacting flows still pose a number of fundamental questions concerning their structure and dynamics often exhibiting surprising behavior. In recent years, the advent of massively parallel high-performance computing has enabled the use of large-scale direct numerical simulations (DNS) for the exploration of the reacting flow dynamics in extreme, previously inaccessible regimes. This talk will discuss the computational requirements and challenges associated with such extreme-scale DNS. Furthermore, we will present an overview of a range of phenomena recently discovered in DNS of high-speed reacting flows characterized by high flow speeds, significant compressibility effects, and strong coupling between exothermic reactions and the flow. Such phenomena include intrinsic instabilities of reacting turbulence, onset of catastrophic transitions, e.g., spontaneous detonation formation, and the qualitative changes in the nature of the turbulent cascade in the presence of exothermic reactions.