On the reduction of state to state chemical-physical models to hybrid macroscopic models in hypersonic flows

The state to state chemical kinetic model, which considers a kinetic equation for each vibrational state of diatomic model, has been applied to some supersonic flow regimes and in particular in boundary layer, nozzle expansion and shock wave. Non equilibrium vibrational distribution obtained in the calculations shows strong departure from equilibrium inducing non Arrhenius global chemical rates, that differ substancially from macroscopic rates commonly used in fluid dynamic codes. The evolution properties of the distribution have been investigated by a zero-dimensional (depending only on time) numerical code in controlled conditions. We are trying to obtain from zero-dimensional results the approach to find appropriate macroscopic rate model to be used in fluid dynamic code accounting for the vibrational nonequilibrium. A comparison of analytical fitting of the zero-dimensional data and fluid dynamic global rates has been performed. © 2005 by G. Colonna.