An Experimental Study on the Interaction Effects between a Rectangular Supersonic Jet and a Flat Wall at Different Wall Lengths

Abstract

Abstract An experimental investigation was undertaken to study the effect of placing a flat wall at the rectangular exit (Aspect Ratio = 2) of a supersonic nozzle on the shock cell structure, and transverse deflection behavior of the jet issuing from the nozzle\(.\) The design exit Mach number (\({M}_{e})\) was 1.8. In the experiments, the length of the wall (\({L}_{w})\) and nozzle pressure ratio (NPR) were varied to explore their effect on the jet interaction with the wall. Schlieren images & wall pressure data obtained from the experiments were used to study shock cell structure and for calculation of two-dimensional normal force and moment coefficients. In over-expansion conditions, the interaction between the jet and the wall caused a downward deflection of the jet up to \({{L}_{w}=D}_{h}\) (hydraulic diameter). Under-expansion conditions of the jet made the jet deflect upward irrespective of the magnitude of \({L}_{w}\) till \({{L}_{w}=8D}_{h}\). The two-dimensional normal force and moment coefficients of the wall were more or less insensitive to the variation in \({L}_{w}\) beyond \({4D}_{h}\). However, for \({L}_{w}\) < \({4D}_{h}\), the jet expansion conditions determined the nature of variation with \({L}_{w}\). The effect of wall was such that reduction in wall-bound supersonic core length was maximum at \({L}_{w}\) = \({0.5D}_{h}\) at over-expansion conditions and at \({L}_{w}\)=\({D}_{h}\) at under expansion conditions.