Internal Aerodynamics of Supersonic Crossflows with Transverse Liquid Injection

TL;DR

This paper experimentally examines the internal aerodynamics of transverse liquid injection in a supersonic crossflow at Mach 2.1, revealing flow phenomena, shock interactions, and the effects of injection configurations on shock reflection modes.

Contribution

It provides new insights into the flow dynamics, shock interactions, and the influence of injection configuration on shock reflection modes in supersonic crossflows with liquid injection.

Findings

Large liquid clumps form downstream, with differences between single and tandem injections.

Transition from regular to Mach reflection depends on injection configuration and momentum flux ratio.

Complex flow regions and vortex structures significantly influence overall flow dynamics.

Abstract

This study experimentally investigates the internal aerodynamics of transverse liquid injection in a supersonic crossflow (Mach (M) = 2.1) using two configurations: single and tandem (8 mm spacing) at three injection mass flow rates. Back-lit imaging revealed classical jet breakup phenomena, including surface wave instabilities with increasing amplitudes along the jet boundary, leading to protrusions, breakup into large liquid clumps, and their disintegration into finer droplets under aerodynamic forces. The single injection exhibited the formation of large liquid clumps further downstream compared to the tandem injection. Schlieren imaging showed that at a low momentum flux ratio (J = 0.94), both configurations produced regular reflection (RR) of the bow shock wave from the top wall. Increasing J to 1.90 resulted in RR for the single injection, while the tandem injection transitioned to Mach reflection (MR). At J = 2.67, both configurations exhibited MR. The earlier RR-to MR transition in tandem injection is attributed to its higher jet penetration and spanwise spread, which reduce the downstream crossflow passage area, acting as a supersonic diffuser and increasing downstream pressure which is favorable for MR transition. Separation zones were observed at the bottom wall due to bow shock wave-boundary layer interaction, and at the side walls due to the interaction of the Mach stem of the MR structure with the walls. These interactions create complex flow regions dominated by vortex structures, significantly influencing the overall flow dynamics.