Three-dimensional AOTV flowfields in chemical nonequilibrium

Abstract

A technique for upwind differencing of the three-dimensional species continuity equations has been presented which permits computation of steady flows in chemical equilibrium and nonequilibrium. The iteration strategy has been demonstrated over a large range of pressures and temperatures. Easily programmed, empirical guidelines for controlling time step in the implicit formulation are also presented. isons with a free-energy-minimization routine serve to justify the equilibrium calculations. Nonequilibrium calculations for flow over spheres of varying radii demonstrate the prediction capabilities of the method over a large range of Damkohler numbers. Calculation of flowfields in near equilibrium present no problem for the method. of chemical species though there is no negative impact of diffusion terms (other than computer time) on the algorithm. Discussions of convergence rates, coupling strategies with the main equation set, and possibilities for improving convergence, reveal a challenging research area both from the point of view of physics and numerical analysis. Compar-The method at present neglects diffusion 'ar'

High-resolution shock-capturing schemes for inviscid and viscous hypersonic flows

“…The form similar to the one used by Gnoffo [35] or Roe and Pike [36] can improve the convergence rate over the ones used in references [37,38]. In all of the computations shown the form Rj+ _ used is the same as in references [37,38] except for an extra factor of 1/c]+½.…”

Surface Recombination Effects on Surface Friction of ReentryVehicles

“…NASA takes lot efforts on numerical simulation and experiment research of reentry vehicles, especially in Lunar Exploration Program and MARS Program, and knowledge of real gas effect on reentry vehicles is obtained [1][2] , that is, surface recombination will dominate at the surface when gas after the bow shock dissociate evidently, atoms transform into molecule and release considerable energy, it is called surface recombination effect. Surface recombination will change the mixture composition and internal energy profile near the wall, the way and how it affects the thermal environment is known to a certain extent [3][4][5] .…”

Visualization of non-equilibrium dissociating flows

“…These must be understood if test data are to be extrapolated accurately to flight conditions. Although numerical methods have been used to calculate equilibrium and non-equilibrium flow around hypervelocity vehicles (1,2), the difficulties inherent in these computations are such that it is not yet possible to model the full chemistry. This deficiency has been recognized for a long time ± see, for example, the studies of nonequilibrium nitrogen flow performed by Hornung (3,4) using a shock tunnel to obtain data for comparison with theoretical predictions from the method of Freeman (5).…”