Fluctuation measurements in the near wake of a wedge with and without base injection

An experimental investigation of the turbulent and transitional near wake of an adiabatic, slender wedge with and without base injection was performed in the Jet Propulsion Laboratory (JPL) supersonic wind tunnel at Mach 4. Two different quantities were measured with a constant current hot-wire anemometer: the mean square fluctuation intensity [f = 0.1 to 80 KC (see Nomenclature)], and the frequency spectrum of the fluctuations (f = 5 to 200 KC, bandwidth Δf = 0.2 KC). The various flow regions of the near wake were identified and the growth and decay of flow fluctuations were determined. The flow fluctuations of the turbulent boundary-layer remnant were found to decay rapidly during the expansion, and the inner shear layers and the reverse flow region, which they bound, were shown to be laminar. Base injection was found to stabilize the near wake and to delay wake transition