The process of ablation for Earth atmospheric entry is simulated using a computational approach that allows thermwchemical nonequilibrium of the flow field and ablation gases. The heat pulse into the heat shield is modeled. The flowfield and graphite heat shield are coupled through surface mass and energy balances. The surface thermochemistry involves the oxidation of graphite and allows for catalytic recombination of diatomic oxygen. Steady-state simulations are performed on a one meter nose radius sphere at a n altitude of 65 km and at freestream velocities of 0 knrls and 10 kmls. A transient simulation is performed at 65 km altitude and a freestream velocity of 10 km/s. Nomenclature CP = h e a t capacity, J / ( k g K ) C S = species mass fraction D = diffusion coefficient, m Z / s E E" F, G !h hs h a , o K w M = Mach number M , P = pressure, N/m2 q = total energy per unit volume, J/m3 = vibrational energy per unit volume, Jim3 = axisymmetric flux vectors = number of vibrational degenerate states = species specific enthalpy, J f k g = species heat of formation, J / k g = species total enthalpy, J / k g = equilibrium constant for reaction r = species molecular weight, kglkmol = translational-rotational heat flux, W/cmz -W X , Y a & P P* n U P P. WS W" T = vibrational heat flux, W/cmz = universal gas constant, 8314.3 J l k m o l . I< = Reynolds Number = Nose radius, 1.0 m = universal gas constant, 82.06-= Schmidt number = translation-rotational temperature, K = averaged temperature, K = vibrational temperature, K = axisymmetric velocities, m / s = vector of conserved quantities = source vector = molar concentration, p,/M, kmol/m3 = axisymmetric coordinates, m = reaction probability = emissivity, 0.9 = mixture viscosity, kg/(m . s) = species viscosity, t g / ( m s) = thermal conductivity, W / ( m . K ) = Stefan-Boltzmann constant, W / ( m 2 . K 4 ) = total density, kg/m3 = species density, kg/m3 = shear stress, N/m2 = chemical source term, kg/(m3 s) = vibrational source term, J / ( m 3 . s) Subscripts: S = denotes species value x, Y = denotes derivative oc, = denotes free-stream value 1 Downloaded by UNIVERSITY OF NEW SOUTH WALES on July 23, 2015 | http://arc.aiaa.org |
