AERONAUTICS AN EXPERIMENTAL INVESTIGATION OF THE BASE PRESSURE CHARACTERISTICS OF NONLIFTING BODIES OF REVOLUTION AT

An investigation was undertaken in the Ames 10- by 14-inch super-sonic wind tunnel to determine some of the base pressure characteristics of related bodies of revolution at zero angle of attack. The basic body shape used in this investigation was a lo-caliber tangent ogive nose section combined with a cylindrical after’body. Other related shapes tested differed in that they had either a blunt-nosed profile or a boat-tailed afterbody. Model fineness ratios were varied from 3.12 to 10 by changing afterbody length. Tests were conducted at free-stream Mach numbers from 2.73 to 4.98 over a Reynolds number range, based on body length, from 0.6 x 106 to 8.8 x 106. In general, the base pressure coefficient decreased with increasing Reynolds number and increased with increasing free-stresm Mach number and fineness ratio. In the particular case of an ogive-cylinder model of fineness ratio 5 with laminar-boundary-layer flow at a Reynolds number of 4 x 106, it was found that the base pressure coefficient was about 60 percent of the limiting value (represented by a vacuum) over the,Machnumber range of the tests. A decrease in the base pressure coefficient, which became more pronounced with increasing Mach nuni%er, accompanied natural transition from laminar- to turbulent-boundarj-layer; flow in the region of the base. This result is in contrast to that obtained at lower supersonic Mach numbers where an increase in base pressure coefficient has been found to accompany transition. The effect on the measured base pressure of the nose-profile shapes investigated was found to be negligible for an afterbody length of 7 body diameters. With turbulent-boundary-layer flow over a body of fineness