Experimental investigation on surface heat transfer characteristics of hypersonic two-dimensional rearward-facing step flow

Hypersonic rearward-facing step flow is one of the basic flow problems in the design of engine for endo-atmospheric hypersonic vehicle, including thermal protection, and aero-optical correction for infrared imaging window of hypersonic interceptors, etc. To know the characteristics of hypersonic rearward-facing step flow is of vital importance in improving the performances of vehicles, and understanding the basis of the flow. This paper investigates the characteristics of a two-dimensional hypersonic rearward-facing step flow, measures the surface heat transfer coefficient and the surface static pressure downstream the step, and compares the results with the values predicted using the hypersonic boundary layer theory. And the results are demonstrated by the flow structure visualization using NPLS (nano-based planar laser scattering) technique. It is concluded that for the hypersonic two-dimensional rearward-facing step flow, the surface heat transfer distribution can be determined directly by the boundary layer edge parameters at the step; and the viscous effect dominates the flow characteristic in the separation and reattachment region; whole in the far-field region downstream the step, the heat transfer coefficient approaches an asymptotic value that may be equal to the turbulent flat plate value. Furthermore, the boundary layer structure may depend on the ratio of boundary layer thickness to the height of step. It is concluded that, when studying the problem of hypersonic rearward-facing step using CFD (computational fluid dynamics) technology, choosing an appropriate turbulent model is needed.