A study of the large-scale structure in a supersonic slot injected flow field

Large-scale structures were studied in a supersonic stream of air (M = 3) with tangential supersonic slot injection of air (M = 1.7). A dual constant temperature hot-wire probe was used to determine the average structure angles and the characteristic length of the turbulent structures. A zero pressure gradient supersonic boundary layer was studied upstream of the slot injection, and results were compared with previously published data. Structure angles on the order of 50° were obtained throughout the majority of the boundary layer, which was consistent with previously published data. The slot injected flowfield was studied at three axial locations (X/H of 4, 10, 20). Two distinct regions were apparent at each station. A region dominated by the upstream supersonic boundary layer resulted in structure angles on the order of 50°. The mixing region between the slot injected flow (M = 1.7) and the tunnel flow (M = 3) resulted in structure angles on the order of 65°. A compression ramp was used to generate a shock between X/H of 10 and X/H of 20. Structure angles obtained at X/H of 20 appeared unaffected by the streamwise pressure gradient. The characteristic length of the turbulent structures in the supersonic boundary layer and the mixing region of the slot injected flowfield were less than 3.5 mm; however, the characteristic length could not be resolved in this region due to limitations imposed by the frequency response of the hot-wire anemometer systems.