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National Advisory Committee for Aeronautics, Technical Notes - Effects Leading Edge Blunting on the Local Heat Transfer and Pressure Distributions Over Flat Plates in Supersonic Flow

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 h 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 l-inch—diameter cylin-
drical leading edge. All tests were performed with the instrumented
surfaces at zero angle of sweep and zero angle of attack.

For the test conditions, 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 investiga-
tions. 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 negli-
gible 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, blunt-
ing 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.