Effects of freestream nonequilibrium on convective heat transfer to a blunt body

Abstract

The axisymmetric Navier- Stokes equations are solved numerically for nonequilibrium airflows over a hemisphere. A formulation with a three-temperature thermochemical model has been employed to simulate vibrationally excited and partially dissociated airflow. A flow condition that has a total enthalpy of 25 MJ/kg and a surface pressure of 0.076 atm is studied. Computed stagnation point heat transfer using finite catalytic boundary conditions at the surface is compared with classical results. Departures from the classical heat transfer predictions caused by nonequilibrium effects are assessed for arcjet testing applications. A Damkohler number analysis is used to characterize the extent of flowfield nonequilibrium. It is shown that characterization of the thermodynamic state of the gas at the boundary-layer edge and within the boundary layer is needed to interpret the heat transfer measurements and to determine the surface catalytic efficiency.