Aerodynamic Performance of Scramjet Inlet Models with a Single Strut

A series of three-dimensional sidewall compression-type scramjet inlet models with single struts were tested in a Mach 4 wind tunnel to investigate the influence of a strut between the sidewalls. With the sidewalls having a fixed shape, five struts of the same width but different lengths and wedge angles were mounted, so that the effect of each model could be compared with the same geometrical contraction ratio. The aerodynamic performances of inlets were determined based on the total pressure efficiency and the mass capture ratio at the geometrical throat. Also, flow visualizations were carried out to examine the flow structure, especially around the strut. Some of the results were compared with previously examined nonstrut models. The additional shock waves generated by the strut created a large separation on the sidewalls and the strut wall, resulting in the reduction of the total pressure efficiency and the capture ratio. Due to this separation, the shock wave was observed to be oscillatory. Measurement of fluctuating wall pressure was also carried out, which revealed that, in some regions, the pressure signals were asynchronous on the left and right sides of the strut. It seems that a small difference of the separation bubble structure on each sidewall initiated a cascade effect of pressure imbalance around the struts.