Development of a Fluid Structure Interaction model for flexible Anti-Sloshing Device

The purpose of this master's thesis project is to develop a Fluid-Structure Interaction model to examine how the flexibility of anti-sloshing devices influences the dynamics of propellant in Vega-E cryogenic tanks. The parameter used for the comparison between the rigid and the flexible cases is the damping coefficient of the forces acting on the tank walls. The analyses are conducted on a shelf-shaped anti-sloshing device inside a parallelepiped shaped tank. The sloshing condition is simulated by imposing a lateral forcing on the tank for a specified time interval. Initially, to establish a baseline understanding of fluid dynamics within the tank, two CFD analyses are compared: one without any baffle and another with an anti-sloshing device assumed to be infinitely rigid. Subsequently the FSI analyses are presented. Various levels of stiffness are tested to understand the influence of the ASD flexibility. This study utilizes the partitioned FSI method with a two-way simulation approach. Ansys Fluent is used for pre-processing to create the entire computational domain, while Ansys Mechanical (transient structural) is employed to determine how a structure dynamically responds to unsteady methane flow. The volume of fluid (VOF) technique in Fluent is used to track the free surface of the fuel phase (cryogenic methane). Finally, the two solvers are coupled using System Coupling. The results show a slight improvement in the damping coefficient when using a flexible ASD, even though occasional wall force amplifications are observed. These amplifications may be attributed to potential phase-aligned oscillations of the free surface of methane and the ASD during that specific time step. Furthermore, it is noted that the frequency of the forces acting on the tank walls is not influenced by the deformation of the device.