An experimental study on the interaction effects between a rectangular supersonic jet and a flat wall at different wall lengths

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). Underexpansion 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.

Effect of wall length on an interacting supersonic rectangular jet

“…Changes in wall length were found to have significant effect on decay characterizes of a square supersonic jet flowing past the wall in the study conducted by Manikanta et al (2022). The interaction effects between a rectangular jet and a flat wall at various wall lengths were found to have significant results in force and moment coefficients up to L w = 4 D h at all nozzle pressure ratios (NPRs) (Manikanta and Sridhar, 2024). Similar situations exist in single expansion ramp nozzle flows in scramjet engines wherein a rectangular supersonic stream flows past a ramp wall.…”