The 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

Design of space vehicles pose many challenging problems due to their hypersonic speeds as they need to travel through different flow regimes due to changes in the density of the atmosphere with altitude. Some of the key characteristics associated with hypersonic flow are extremely high temperatures and heat transfer to the wall of the spacecraft. At these temperatures, the assumption of thermal equilibrium is no longer valid and the effect of rotational non-equilibrium must be included in the modeling of diatomic gas flow. This thesis 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 an axisymmetric blunt body and a bicone for various levels of rarefaction—including the rotational non-equilibrium effect. The customized flow solver, ZLOW, is used to calculate the numerical solutions for laminar viscous hypersonic flow past a blunt body and a bicone at Knudsen numbers Kn in continuum-transition regime with and without rotational non-equilibrium. The effects of rarefaction in the continuum-transition regime are modeled by applying the Maxwellian velocity slip and temperature jump boundary conditions on the surface. The effects of the rotational non-equilibrium terms are discussed in this thesis for both the continuum (Kn = 0) and slip flow regime (Kn \u3c 0.1). In addition, both the blunt body and bicone 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