Shock and shear layer interactions in a confined supersonic cavity flow

The impinging shock of varying strengths on the free shear layer in a confined supersonic cavity flow is studied numerically using the detached eddy simulation. The resulting spatiotemporal variations are analyzed between the different cases using unsteady statistics, x-t diagrams, spectral analysis, and modal decomposition. A cavity of length to depth ratio [ L / D ] = 2 at a freestream Mach number of M infinity = 1.71 is considered to be in a confined passage. Impinging shock strength is controlled by changing the ramp angle (theta) on the top wall. The static-pressure ratio across the impinging shock ( p 2 / p 1) is used to quantify the impinging shock strength. Five different impinging shock strengths are studied by changing the pressure ratio: 1.0 , 1.2 , 1.5 , 1.7, and 2.0. As the pressure ratio increases from 1.0 to 2.0, the cavity wall experiences a maximum pressure of 25% due to shock loading. At [ p 2 / p 1 ] = 1.5, fundamental fluidic mode or Rossiter's frequency corresponding to n=1 mode vanishes whereas frequencies correspond to higher modes (n=2 and 4) resonate. Wavefronts interaction from the longitudinal reflections inside the cavity with the transverse disturbances from the shock-shear layer interactions is identified to drive the strong resonant behavior. Due to Mach reflections inside the confined passage at [ p 2 / p 1 ] = 2.0, shock-cavity resonance is lost. Based on the present findings, an idea to use a shock-laden confined cavity flow in an enclosed supersonic wall-jet configuration as passive flow control or a fluidic device is also demonstrated.

Automated summary

The study numerically investigates the impact of impinging shock waves of varying strengths on the free shear layer in a confined supersonic cavity flow. As the strength of the shock waves increases, the pressure on the cavity wall also increases, exhibiting resonant behavior.