Numerical studies on the effect of the key parameter to hypersonic "pitch-up anomaly"

Abstract

Real-gas effects, e.g., vibrational excitation, dissociation and ionization of air, are critical issues in the hypervelocity flow around a reentry vehicle. In this work, a chemical and thermal nonequilibrium Euler solver is used to evaluate the real-gas effects on the aerodynamic forces of a typical hypervelocity test model. It is found that using an inert gas model with a lower specific heat ratio to simulate the real-gas effects may cause an under prediction of the forces and the pitching moment. Comparative simulations indicate that dissociation results in much more significant difference to the aerodynamic performance than the vibrational excitation. It is also found that the streamwise inhomogeneity of chemistry in the flowfield instead of the decreased specific heat ratio is the primary reason of Pitch-up anomaly.