Numerical Simulations of Acoustic Resonance of Solid Rocket Motor

Low amplitude but sustained pressure and thrust oscillations can characterize the quasi-steady condition of solid rocket motor; notwithstanding they are not threatening for motor life, coupling to the structural modes, they can damage the payload. These oscillations are due to fluid dynamics instabilities and acoustic coupling. To correctly predict the oscillatory level, a numerical model has to include ad hoc model for: two-phase flow, propellant combustion response to oscillatory conditions, turbulence, deformation of inhibitor rings under aerodynamic load, two-phase flow, propellant type (i.e. HTPB propellants). To obtain a good prediction, all these aspects can not be neglected and has to be modelized; this necessity determines a considerable model complexity added to enormous computational costs and times. In this paper the AGAR (Aerodynamically Generated Acoustic Resonance) code is presented, a simplified method to predict both oscillation frequencies and amplitude with reduced computational costs and times, describing the excitation of acoustic modes account- ing for the acoustic feedback on the vortex shedding phenomenon. A brief description of the method and of the principal obtained numerical results is presented.