THE FLOW FIELD AND HEAT TRANSFER DOWNSTREAM OF A REARWARD FACING STEP IN SUPERSONIC FLOW
AEROSPACE RESEARCH LABS WRIGHT-PATTERSON AFB OH
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An experimental investigation of the flow field, and the model pressure and steady-state heat transfer distributions for a rearward-facing step in supersonic flow is described. Tests were conducted using a water-cooled model with a step height adjustable to 0.443 and 0.750 inches at free stream Mach numbers of 2.5, 3.5, and 5.0, and at Reynolds numbers based on length of surface ahead of separation of approximately 250,000 to 1,800,000. It was found that the Reynolds number based on step height is an important parameter and that both the base pressure and the maximum heat transfer at reattachment may be predicted as a function of this parameter. Several representative flow fields are presented along with analyses of the various regions of these fields. It was found that the depressed base pressure is communicated upstream of the step through the subsonic portion of the attached boundary layer resulting in a pressure gradient immediately upstream of the step. It is shown that the rapid corner expansion is not the commonly used Prandtl-Meyer expansion, but rather is accurately described by the method of inviscid rotational characteristics which accounts for both the entropy gradient in the boundary layer and the pressure gradient upstream of the step. This description of the corner expansion also accurately predicts the position of the lip shock associated with the rapid expansion.
- Fluid Mechanics