Observations on the structure of an edge-tone flowfield

The unsteady flowfield in the region in which a rectangular jet interacts with the leading edge of a 20-deg wedge is investigated experimentally. Edge-tone flowfields at Mach 0.8 in the blowdown facility at Stanford University are recorded by phase-locked Schlieren photography using the apparatus and techniques described by Krothapalli and Horne (1984); detailed surface-pressure and velocity measurements are obtained at Mach 0.23 in the NASA Ames anechoic-chamber facility and presented graphically. It is shown that the jet-edge interaction produces a secondary vortex at the leading edge when an established shear layer or primary vortex is present, and that the primary and secondary vortices then evolve from a counterrotating vortex pair to a large single vortex which migrates along the wedge surface (in agreement with the observations of Rockwell et al., 1986). From a comparison with data on airfoil-trailing-edge flows (Satyanarayana, 1977) it is inferred that an instantaneous zero pressure differential is present at the leading edge of the wedge.