Base Pressure of Spheres and Supersonic Speeds.
NAVAL ORDNANCE LAB WHITE OAK MD
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Base-pressure measurements were made on spheres with diameters from 0.7925 to 19.99 cm at M 1.57 to 5.0 to study Mach and Reynolds number effects between Re 0.06 x 10 to the 6th power and 1.4 x 10 to the 6th power. The data showed that the base-pressure component of the total-drag coefficient is a function of the Reynolds number and can be affected by boundary-layer disturbances. The estimated Reynolds number effect on the total-drag coefficient was very small a maximum of 10 at M 1.57 and a minimum of 1 at M 4.24. The effects of Mach number on wave- and base-drag coefficients cancelled each other so that the total-drag coefficient was almost independent of Mach number. The good agreement between wake configurations determined from wind-tunnel schlieren photographs and firing-range shadowgraphs at correponding Mach and Reynolds numbers suggested the extension of comparative tests with spheres to higher Reynolds numbers in both the wind tunnel and firing range. The failure to detect a critical Reynolds number for spheres at supersonic speeds was attributed to supersonic turbulent separation effects similar to those for subsonic regions.