Effect mechanism of dielectric barrier discharge plasma excitation layouts on vortex-induced pressure oscillations in solid rocket motors

Vortex-induced pressure oscillations in the combustion chambers of solid rocket motors represent a critical challenge to their reliability, and traditional passive control methods struggle to actively regulate the flow instability process. Taking a current experimental motor, C1x, as a reference, this paper employs a numerical methodology that couples large eddy simulation with a dielectric barrier discharge plasma model to systematically investigate the suppression mechanism of plasma excitations on vortex-induced pressure oscillations. The results show that the effect of plasma excitations on pressure suppression does not exhibit a linear superposition relationship with increasing axial number. Under the condition that the plasma excitation intensity is set to 15, the double-row axial arrangement reduces the relative amplitude of pressure oscillations at the main frequency from 0.08% (single-row) to 0.030%. This demonstrates that the suppression effect of the double-row plasma arrangement is significantly superior to that of the single-row arrangement overall. The number of circumferential plasma excitations has no significant effect on suppressing pressure oscillations in the motor. The closer the excitation position is to the backward-facing step where the vortex is generated, the more strongly the induced vortices there are broken, enhancing the suppression of pressure oscillations. A plasma excitation located at twice the boundary layer thickness upstream from the step achieves optimal pressure oscillation suppression. Compared with an incidence direction parallel to the mainstream, vertical and opposite-direction plasma incidence yields a higher vortex rotation intensity and better suppression, which can reduce the maximum relative amplitude of pressure oscillations from 0.07% to 0.027%.