An analytical study on nonequilibrium dissociating gas flow behind a strong bow shockwave under rarefied conditions

Abstract

In this paper, an explicitly analytical shock mapping relation is approximately deduced based on the theoretical modeling of the chemical nonequilibrium stagnation flow towards a slightly blunted nose. Based on the relation, the complex reacting stagnation flow problem can be discussed under the framework of the simplest normal shockwave flow. Therefore, a quantitatively meaningful criterion for dissociation nonequilibrium flow, that is a specific Damkohler number Dad, is naturally introduced as the ratio of the mapping length of the stagnation streamline and the characteristic nonequilibrium scale. Dad is found to be dependent on the flow’s rarefaction criterion Wr, that is a specific Knudsen number. Then, based on Dad, a normalized analytical formulation is obtained to quantitatively predict the actual degrees of dissociation at the outer edge of the stagnation point boundary layer (SPBL). At last, the direct simulation Monte Carlo (DSMC) method is employed to validate the analytical results, and the related flow mechanism is discussed. The present study not only shows nonequilibrium features of the flow problem, but also provides an indispensable basis for the following study on the nonequilibrium SPBL heat transfer.