Local bridging to predict aerodynamic coefficients in hypersonic, rarefied flow

Abstract

A computational method is given for the prediction of local pressure and viscous shear stress on windward surfaces of convex, axisymmetric or quasi-axisymmetric, hypersonic bodies in the transitional, rarefied flow regime. Overall aerodynamic forces and moments are computed by integration of the local quantities. The method is based on a correlation of local pressure and shear stress computed by the direct simulation Monte Carlo (DSMC) numerical technique for cold-wall, real-gas conditions and some supplemental data from low-density, hypersonic wind tunnels. Two-dimensional shapes and leeward surfaces are not included in the scope of the method as it is presented here. Results are compared with DSMC and viscous shock layer computations for both local and overall coefficients. Also included are sphere and blunt cone drag obtained from both computation and experiment, as well as lift and pitching moment coefficients for the NASA Aeroassist Flight Experiment vehicle at various angles of attack. It appears that the method presented here will prove adequate for relatively bluff bodies approximately defined by wetted length-to-nose radius ratios of less than 10.