Nitrogen dissociation rates in complex hypersonic flows

Current models for the dissociation rate and the vibration-dissociation coupling process are used to simulate several recent hypervelocity experiments. It is shown that all of the models accurately predict the shock standoff distance for a spherical, blunt-body flow. However, the computational results do not agree with a set of experiments that was designed to be sensitive to the chemical kinetics model. In these highly separated flows, the equilibrium dissociation rate must be increased or decreased by a factor of about four to obtain reasonable agreement with the data. This puts into doubt the accuracy of the reaction rate, or indicates that some other unknown thermo-chemical process occurs in these flows.