NUMERICAL INVESTIGATION OF THE EFFECT OF WALL TEMPERATURE ON THERMAL ENVIRONMENT OF TWO-DIMENSIONAL TRANSVERSE GAP

By solving the compressible Navier-Stokes equations, a CFD software is developed independently, which can well simulate the flow in the gap in hypersonic vehicle surface. An analytical study has been performed through this software to investigate the wall temperature effects on thermal environment of two-dimensional transverse gap, and the mechanism of the influence is also analyzed. The research indicates that the influence of wall temperature change on thermal environment mainly comes from two aspects：one is to change the wall temperature gradient directly, the other is to change the physical parameters near the wall, and then change the whole flow structure. The joint action of the two aspects determine the variation law of the heat flux distribution. For the gap flow, the local high heat flux regions are mainly caused by the reattachment flow. On the one hand, increasing the wall temperature will reduce the wall temperature gradient, which will lead to the decrease of the heat flux; on the other hand, it will increase the viscosity coefficient near the wall, thicken the boundary layer, enhance the viscous dissipation, restrain the separation and reattachment flow at the entrance of the gap and the vortexes flow in the gap, which will greatly reduce the corresponding heat flux peak value. The hot wall correction formula widely used in engineering application ignores the influence of wall temperature on the flow structure. So the local heat protection design using the hot wall correction formula will produce a large deviation.