SLAMMING IMPACT SIMULATION OF 2D WATER ENTRY FOR RIGID STRUCTURES

What is it about?

Slamming impact is considered important factor for ship design engineers to predict the structural reliability under maximum pressure and hydrodynamic forces in a small duration of time. In this paper, we deal with rigid bodies by simulated 2D water entry problem based on Arbitrary Lagrangian Eulerian (ALE) built-in explicit finite element in Abaqus software. To validate the efficiency of models, various deadrise angles are applied from 4° to 80° for wedge. The prediction of maximum pressure and hydrodynamic forces are compared with the analytical formulations of the rigid body. Many factors are affecting on slamming phenomenon due to high deformation in the fluid. Therefore we have delineated the effect of the contact stiffness factor between the fluid and structure in penalty contact method, which influences on the results. Fluid domain mesh sizes convergence are applied with take in consideration the hourglass control effect, showed that the effect of the density of the mesh has high influence on the amplitudes stability for both pressure and force.

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Why is it important?

In this study we are simulated the water entry for 2D rigid structure by using ALE (Arbitrary Lagrangian-Eulerian) solver, which can be represented the solid deformation as fluid with water properties. ALE combines the properties of Lagrangian and pure Eulerian using the adaptive mesh technique, and can be remap the mesh with each step increment to prevent the distortions of the mesh due to high deformations. This technique is depending on the coupling contact, therefore, penalty contact method have been used. By defining the appropriate parameters for this method such as stiffness scaling factor and mesh density, it can be satisfied the stability and prevented the penetration between the rigid body and the water. When compared these simulations with previous methods, a good agreement can be observed between the measured impact pressures for deadrise angles large than 30° and the analytical methods. Noted that high pressure peak close to move to the keel of the wedge, and it was dropped with increase the deadrise angle. For the deadrise angles less than 10°, some difference are happen compared with the analytical methods, and pressure with sharply peak occurs close to the jet flow region. The pressure peak for a wedge body is stay unchanged approximately along the wedge-water interface with time histories and it is reducing after the flow separation happens.

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