Experiments on two-dimensional base flow at subsonic and transonic speeds

Abstract

A report is presented of a series of experiments aimed at an investigation of the fundamental mechanisms of the flow behind an isolated blunt-trailing-edge section, and a rearward-facing step, at subsonic and transonic speeds. Pressure measurements and flow photography formed the principal research tools, but in connection with the tests on the isolated section an extensive wake exploration and a study of the vortex-shedding process were carried out. Tests were also made of simple devices which interfere with the formation of the vortex street. These tests are useful both from a basic research aspect and insofar as they indicate possible methods of reducing base drag. A careful study is made of the events which are associated with the transition, at transonic speeds, from the subsonic vortex-street regime to the supersonic steady-flow regime. The tests on the step were aimed chiefly at providing information on the non-periodic base flow which would exist behind a blunt-trailing-edge aerofoil section at subsonic and transonic speeds if the formation of the vortex street could be inhibited.