Effects of rarefaction and thermal non-equilibrium on a blunt body and a bicone in hypersonic flow and their shape optimization for reducing both drag and heat transfer

Abstract

Design of space vehicles poses technical challenges at hypersonic speeds since they need to travel through different flow regimes due to density changes in the atmosphere with altitude. Some key characteristics associated with hypersonic flow include very high temperatures and heat transfer to the wall. At these temperatures, the assumption of thermal equilibrium is no longer valid and the effect of rotational non-equilibrium should be included in modeling of diatomic gas flow. This paper employs the Navier-Stokes equations, which are modified to include a rotational non-equilibrium relaxation model to analyze the heat transfer, drag, and shock standoff distance for hypersonic flow past a blunt body and a bicone for various levels of rarefaction. The customized flow solver, ZLOW, is used to compute the solutions. The effects of rarefaction are modeled by applying Maxwell’s velocity slip and temperature jump boundary conditions on the body surface. In addition, both the blunt body and bicone shapes are optimized in hypersonic rarefied flow with rotational non-equilibrium by using a multi-objective genetic algorithm (MOGA) for reduction of both drag and heat transfer.