On the use of reduced chemical kinetics for hypersonic transition and breakdown to turbulence computations

In high temperature hypersonic boundary layers, chemical reactions among air constituents can affect transition and subsequent breakdown to turbulence. It is vital that the chemical kinetic sets used in hypersonic transition and turbulence computations not only be adequately accurate, but also be computationally viable. Reduced chemical kinetic schemes, if applicable, can substantially reduce the computational stiffness of flow-chemistry interaction calculations. In this work, we attempt to establish that the commonly used five-species, seventeen-reaction chemical kinetic set posses a strongly attracting slow manifold that can be exploited for the purpose of reduced chemistry. Further, we evaluate two reduction methods: (i) quasi-steady state approximation (QSSA), and (ii) locally linear approximation (LLA) to approximate the slow manifold of a high temperature air mixture. While the performance of QSSA is good only near the equilibrium point, the performance of LLA is excellent over a wide range of temperature. Overall, our results indicate that hypersonic external computations can benefit from chemistry reduction strategies. 2011 by Sharath S. Girimaji.

On the use of reduced chemical kinetics for hypersonic transition and breakdown to turbulence computations Conference Paper