Coupled Fluid-Structure Interaction Analysis of Solid Rocket Motor with Flexible Inhibitors

Flexible inhibitors are used in solid rocket motors to control the burning of a propellant, and vortices generated by propellant flow around the inhibitors have been identified as a driving source of instabilities that can lead to thrust oscillations in launch vehicles. Potential coupling between the thrust oscillations and structural vibration modes is an important risk factor in launch vehicle design. To better understand these phenomena, a fluid-structure interaction simulation capability has been developed, and this paper describes its application to investigate multidisciplinary phenomena of flexible inhibitors inside solid rocket motors. The features of the fluid and structural solvers, along with the multidisciplinary coupling methodology, are presented in a general Eulerian-Lagrangian framework. The fluid domain is discretized using general polyhedral unstructured meshes, and full three-dimensional shell elements are used in the structural domain for the inhibitors. Verifications for the structural model show excellent agreement with analytical solutions, and coupled results show that, because of acoustic coupling, the dynamics of one of the most flexible inhibitors shift from its first modal frequency to the first acoustic frequency of the solid rocket motor. This demonstrates that the capability can provide valuable insights into how the dynamics of the inhibitor can affect the flowfield, which can influence solid rocket motor design.