Numerical analysis on vortex acoustic coupling characteristics in solid rocket motors

In order to discover the mechanism of vortex sound coupling in solid rocket motors, large-eddy simulation with wall-adapting local eddy-viscosity subgrid-scale turbulence model was carried out to study the oscillation flowfield induced by obstacle vortex shedding on the foundation of VKI experimental motor. Several cases with various inlet temperatures were presented to investigate parameters which impact the oscillation characteristics. Velocity profiles, vortex shedding frequencies, acoustic frequencies and oscillation amplitude were obtained, and then compared with the experimental data. The results indicate that it is not a necessary condition that vortex shedding frequency equals one acoustic frequency when vortex sound coupling happens. It is not the mean Mach number but velocity magnitude in the combustion chamber mainly that affects on the vortex shedding frequency. Meanwhile, the oscillation amplitude is mainly determined by the mean Mach number.