Comparative investigation of strut cavity and wall cavity in supersonic flows

Cavities have been extensively studied as flame holding devices for scramjets. Wall cavities are known to have issues of fuel nonuniformity and flame close to the wall. Although strut offers an option to deliver fuel in the core flow, it lacks the mixing efficiency provided by the cavity. This work attempts to combine a strut and a cavity into a strut cavity and compare it with the wall cavity for different Mach numbers and aspect ratios, using numerical simulations. Flow features, vortex movement, and oscillation behavior are investigated and compared. Both cavities exhibited oscillations for lower values of Mach numbers and aspect ratios, while oscillations were found to decrease for high values. The wall cavity showed a higher propensity to oscillations compared to the strut cavity. The process regarding the generation of the waves inside the cavity has been revisited. Both the unstable shear layer and the vortex shedding contribute to the generation of the waves inside the cavity. This merges the previous two theories on the wave generation inside the cavity in the supersonic flows.