Theoretical Modeling and Numerical Study for Thrust-Oscillation Characteristics in Solid Rocket Motors

To discover thrust-oscillation characteristics in solid rocket motors, analytical modeling and numerical simulation are carried out by an experimental motor in the von Karman Institute for Fluid Dynamics. The numerical method by means of a mesh sensitivity analysis is proposed for validation. Velocity profiles, oscillation frequencies, and pressure amplitudes were obtained by numerical simulations and then compared with the experimental data. Various cases with different inlet temperatures are proposed to investigate the influences of parameters on the oscillation characteristics. The results indicate that it is not a necessary condition for vortex-shedding frequency to approach a certain acoustic frequency when periodic oscillations are generated. Oscillations are more severe if the vortexshedding phenomenon couples with high-order acoustic modes. Velocity magnitude in the combustion chamber is the main factor that influences the vortex-shedding frequency; meanwhile, the pressure amplitude is mostly determined by the mean Mach number. Theoretical modeling in conjunction with numerical calculations proves that the ratio of dimensionless thrust amplitude to pressure amplitude is predominantly determined by the throat-to-port-area ratio J, and it varies inversely as J. An integrated formula is presented to describe the relationship between thrust amplitude and pressure amplitude.