Studies on effect of head cavity on resonance damping characteristics in solid rocket motors

In order to discover the effect of head cavity on resonance damping characteristics in solid rocket motors, large-eddy simulations with Wall-Adapting Local Eddy-viscosity subgrid scale turbulent model are implemented to study the oscillation flow field induced by vortex shedding on the foundation of VKI (von Kármán Institute) experimental motor. The numerical method by means of a mesh sensitivity analysis is proposed for validation. Pressure oscillation frequencies and amplitudes are obtained, and then compared with the experimental data. It is investigated that oscillation amplitudes reduce remarkably after adding a cavity at the head-end. The results indicate that cavity volume, location and configuration have cooperative effect on the oscillation amplitude. Rayleigh criterion is proved to be of guiding significance of resonance damping. The substance of altering grain configuration is a comprehensive process of adding and abstracting mass. The suppression effect is not caused by the complicated flow field at the head-end. Additionally, it is neglected whether altering grain configuration at the acoustic pressure node. It is concluded that large mass flux added at pressure antinode could attribute to significant amplitude; meanwhile, the damping effect of cavity is stronger if the distance between cavity and pressure antinode becomes shorter. At last, this method is adopted by an engineering solid rocket motor. Ground test reflects that the oscillations are suppressed by the head cavity.