Implicit Large-Eddy Simulation of Solid Rocket Motors using the Immersed Boundary Method

We explore the potential of the immersed boundary (IB) method to predict pressure oscillations in solid rocket motors (SRM) by performing three-dimensional, high-fidelity simulations of two different configurations, including a small, laboratory-scale motor (ONERA C1xb) and a large-scale aft-finocyl SRM with a star grain geometry, inspired to real motors used in space launch vehicles. The implicit large-eddy simulation (ILES) approach is adopted to capture the coupling between vortex shedding and the acoustic chamber modes. The C1xb SRM is studied at its configuration with 3mm burned grain, close to the ignition phase of the motor. The unsteady wall-pressure signal analysis is employed to characterize turbulence effects on the pressure fluctuations. The results are compared with experimental data available in literature. This test case is used to assess the capability of the IB method to simulate the SRM flow. Then, a large-scale aft-finocyl motor is studied at the initial phase of the burning. The flowfield obtained with the IB approach is characterized by parietal vortex shedding (PVS) and the pressure fluctuations sampled at the head-end of the motor are similar to that obtained by flight data of similar SRMs.