Creager, Marcus O
An investigation of the effect of leading-edge thickness on the flow over flat plates with square and cylindrical blunting was conducted at a Mach number of 4 and free-stream Reynolds numbers per inch of 2380 and 6600. Surface pressures were measured on a series of models whose leading-edge thicknesses ranged from 0.25 to 1 inch. Heat-transfer rates were measured from a flat plate which was blunted by a 1-inch-diameter cylindrical leading edge. All tests were performed with the instrumented surfaces at zero angle of sweep and zero angle of attack. For the test condition, the bow shock wave was detached and leading-edge shape had no effect on surface pressures aft of two leading-edge thicknesses. The surface pressures could be predicted by a combination of shock-wave boundary-layer interaction theory and blast wave theory. This combination applied equally well to similar data of other investigations. An empirical expression for local Reynolds number at the boundary-layer edge was found to correlate both the present data and data from other investigations covering a wide range of conditions. The local Reynolds number per inch was found to be lower than free-stream Reynolds number per inch, nearly constant for the test length, and to have negligible dependence on leading-edge bluntness. This reduction depends on the square root of the ratio of total pressures across the normal bow shock wave. The local Nusselt number was found to depend only on the local Reynolds number for the present tests, and is predicted by the familiar Pohlhausen flat-plate theory. As compared to the sharp condition, blunting the leading edge of flat plates, with consequent reduction of local total pressure, was found to increase the heat-transfer coefficients in the region where surface static pressures were high and to reduce the coefficients where the surface static pressures approached the free-stream value.
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