Hydroelastic Impacts of Deformable Wedges

This work investigates the slamming phenomenon experienced during the water entry of deformable bodies. Wedges are chosen as reference geometry due to their similarity to a generic hull section. Hull slamming occurs when a ship re-enters the water after having been partially or completely lifted out the water. There are three more cases commonly defined as slamming phenomena: bow-flare, wet-deck and green water slamming. These are all special cases of the general topic of water entry of a body. While the analysis of rigid structures entering the water has been extensively studied in the past and there are analytical solutions capable of correctly predicting the hydrodynamic pressure distribution and the overall impact dynamics, the effect of the structural deformation on the overall impact force is still a challenging problem to be solved. In fact, in case of water impact of deformable bodies, the dynamic deflection could interact with the fluid flow, affecting the hydrodynamic load. This work investigates the hull-slamming problem by experiments and numerical simulations of the water entry of elastic wedges impacting on an initially calm surface with pure vertical velocity. The objective is to determine an accurate model to predict the overall dynamics of the wedge and its deformations. More than 1,200 experiments were conducted by varying wedge structural stiffness, deadrise angle, impact velocity and mass. On interest are the overall impact dynamics and the local structural deformation of the panels composing the wedge. Alongside with the experimental analysis, numerical simulations based on a coupled Smoothed Particle Hydrodynamics (SPH) and FEM method are developed. Ranges of applicability of a simplified model neglecting the air are found. The results provide evidence of the mutual interaction between hydrodynamic load and structural deformation. It is found a simple criterion for the onset of fluid structure interaction (FSI), giving reliable information on the cases where FSI should been taken into account. The occurrence of ventilation and cavitation varying the impact parameters are also outlined.

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