Fluid-Structure Interaction; Numerical Modelling andExperimental Comparison

Abstract: The purpose of this thesis is to investigate the effects of fluid-structure interaction on a submerged oscillating structure. It is to be determined whether it is possible to model such effects with acoustic fluid elements in LS-DYNA using Mat\_Acoustic. Experiments of an oscillating submerged box were performed and the results were used to compare simulations of the same setups. The setups comprised of 4 different oscillating frequencies and the optional addition of a plate inducing more fluid-structure interaction. From the experiments, an analysis of the rate of decay was performed and a two term exponential model was proposed. The results showed that added mass is consistently underestimated by 15\% in the FE-model. Furthermore the plate resulted in an increase of added mass for the experiment and the FE-model. Additionally, convergence studies regarding the required fluid volume to assume infinite depth and fluid mesh sizing were performed and the results were presented as dimensionless quantities. General guidelines on how to use Mat\_Acoustic and maintain stability were presented. Structure shell elements proved to be particularly difficult to model in terms of stability.