Numerical and experimental investigation of the geometrical scale effect on a confined subsonic-supersonic shear layer

The evolution characteristics of confined subsonic-supersonic shear layers have been investigated experimentally employing the schlieren system and numerically using the large eddy simulation (LES) method under different geometrical scales, including the height of combustion chamber, the thickness of splitter plate, and the exit height of nozzle for the supersonic stream. The LES results are in good agreements with the experimental data for the distributions of velocity and turbulent intensity profiles as well as the schlieren image. From the experiments, the "shock train" structures are found in the middle supersonic flow, which would interact with the shear layers, to thicken the thickness locally and generate the "wave" structures in the internal edges of shear layers. Besides, the LES results indicate that the normalized confined height (h/H) would chiefly affect the development of shear layer, and it will grow better for the h/H being less than 0.133. Under the same h/H condition, the higher height of combustion chamber could promote the growth of shear layer. And the thicker splitter plate could primarily intensify the transverse fluctuations of shear layer to enhance the three-dimensional features. Whereas, the height increase of nozzle exit for the supersonic stream has little improving on the development of shear layer.