Effects of sidewalls and leading-edge blowing on flows over long rectangular cavities

TL;DR

This study uses large eddy simulations to analyze how sidewalls and leading-edge blowing influence flow characteristics over long rectangular cavities, showing that these factors can significantly reduce flow oscillations and pressure fluctuations.

Contribution

It introduces the application of 3D slotted jets along the cavity leading edge to effectively suppress flow oscillations and vortex roll-ups in long rectangular cavities.

Findings

Sidewalls reduce pressure fluctuations by interfering with vortex roll-ups.

Increasing Mach number decreases flow oscillations.

Leading-edge jets significantly reduce pressure and velocity fluctuations.

Abstract

The present work investigates sidewall effects on the characteristics of three-dimensional (3D) compressible flows over a rectangular cavity with aspect ratios of $L/D=6$ and $W/D=2$ at $Re_D=10^4$ using large eddy simulations (LES). For the spanwise-periodic cavity flow, large pressure fluctuations are present in the shear layer and on the cavity aft wall due to spanwise vortex roll-ups and flow impingement. For the finite-span cavity with sidewalls, pressure fluctuations are reduced due to interference to the vortex roll-ups from the sidewalls. Flow oscillations are also reduced by increasing the Mach number from 0.6 to 1.4. Furthermore, secondary flow inside the cavity enhances kinetic energy transport in the spanwise direction. Moreover, 3D slotted jets are placed along the cavity leading edge with the objective of reducing flow oscillations. Steady blowing into the boundary layer is considered with momentum coefficient $C_\mu=0.0584$ and $0.0194$ for $M_\infty=0.6$ and $1.4$ cases, respectively. The three-dimensionality introduced to the flow by the jets inhibits large coherent roll-ups of the spanwise vortices in the shear layer, yielding $9-40\%$ reductions in rms pressure and rms velocity for both spanwise-periodic and finite-span cavities.