Rate Effects in Hypersonic Flows

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Hypersonic flows are energetic and result in regions of high temperature, causing internal energy excitation, chemical reactions, ionization, and gas-surface interactions. At typical flight conditions, the rates of these processes are often similar to the rate of fluid motion. Thus, the gas state is out of local thermodynamic equilibrium and must be described by conservation equations for the internal energy and chemical state. Examples illustrate how competition between rates in hypersonic flows can affect aerodynamic performance, convective heating, boundary layer transition, and ablation. The conservation equations are outlined, and the most widely used models for internal energy relaxation, reaction rates, and transport properties are reviewed. Gas-surface boundary conditions are described, including finite-rate catalysis and slip effects. Recent progress in the use of first-principles calculations to understand and quantify critical gas-phase reactions is discussed. An advanced finite-rate carbon ablation model is introduced and is used to illustrate the role of rate processes at hypersonic conditions.

Original languageEnglish (US)
Pages (from-to)379-402
Number of pages24
JournalAnnual Review of Fluid Mechanics
StatePublished - Jan 5 2019

Bibliographical note

Funding Information:
This work was sponsored by the Air Force Office of Scientific Research (AFOSR) under grants FA9550-16-1-0161, FA9550-17-1-0057, and FA9550-17-1-0250. The views and conclusions contained herein are those of the author and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the AFOSR or the US Government. The author would like to thank Joseph Brock, Ross Chaudhry, Ioannis Nompelis, and Thomas Schwartzentruber for helpful comments.

Publisher Copyright:
Copyright © 2019 by Annual Reviews. All rights reserved.


  • aerothermodynamics
  • finite-rate processes
  • high-temperature gas dynamics
  • hypersonic aerodynamics
  • nonequilibrium flows


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