Flight-Measured Pressure Characteristics of Aft-Facing Steps in High Reynolds Number Flow at Mach Numbers of 2.20, 2.50, and 2.80 and Comparison With Other Data

摘要

An experiment was conducted on the YF-12 airplane to determine the pressure characteristics associated with an aft-facing step in high Reynolds number flow for nominal Mach numbers of 2.20, 2.50, and 2.80. Base pressure coefficients were obtained for three step heights. The surface static pressures ahead of and behind the step were measured for the no-step condition and for each of the step heights. A boundary layer rake was used to determine the local boundary layer conditions.nThe Reynolds number based on the length of flow ahead of the step was approximately 108, and the ratios of momentum thickness to step height ranged from 0.2 to 1.0. Base pressure coefficients from the present study are compared with other available data at similar Mach numbers and at ratios of momentum thickness to step height near 1.0. In addition, the data are compared with base pressure coefficients calculated by a semiempirical prediction method. The base pressure ratios are shown to be a function of Reynolds number based on momentum thickness. Profiles of the surface pressures ahead of and behind the step and the local boundary layer condi¬tions are also presented.