Experiments on two-dimensional base flow at M = 2.4

Abstract

This report gives an account of experiments carried out on a family of two-dimensional afterbodies to determine the effect of boat-tail angle and internal flow on the base pressure, the afterbody pressure, and the velocity distribution in the wake. The afterbodies tested were of constant length with boat-tail angles of 0, 2½, 5, 7½ and 10 deg respectively. Each member of this series was mounted on a common model screwed to the upper surface of a flat plate placed at zero incidence in a uniform supersonic stream of Mach number 2.41. The inside of the model, which was hollow, was shaped in the form of a plenum chamber tapering towards the rear to a two-dimensional convergent nozzle with a parallel throat exhausting into the region behind the base. This nozzle was supplied with dry air at 20 deg C bled from the main tunnel supply. Measurements were made of the afterbody pressure distribution, the base pressure, and the velocity distribution in the wake for each member of the family over a range of internal flow extending from no flow to tpj/p∞ = 11. Further information on the base flow with the untapered afterbody was also provided by measurement of the effect of internal flow on the plate pressure distribution behind the base. In all cases these pressure measurements were supplemented by schlieren photography. In the concluding sections of the report the results are analysed and discussed in detail both from the theoretical aspect and also with regard to their practical application.