An improved particle method for simulations of slamming with fluid-structure interaction

Zha, Ruosi (2021) An improved particle method for simulations of slamming with fluid-structure interaction. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (102MB)

Abstract

It is important to study the wave impact and slamming problems, involving breaking free surface, which can cause high impact pressure and therefore structural damage on ship hulls and offshore platforms. An improved higher-order moving particle semi-implicit (MPS) method was developed to solve 2-D water entry problems. To overcome the inconsistency in the original MPS methods, a pressure gradient model was modified to guarantee the first-order consistency and to satisfy the conservation of momentum simultaneously. A particle shifting technique was also applied to improve the numerical stability. Validation studies were carried out for water entry of a rigid wedge with a deadrise angle of 30ﾟ and the tilt angles of 0ﾟ, 10ﾟ and 20ﾟ and two rigid ship sections. Convergence studies were conducted on domain size, particle spacing and time step. A Particle Convergence Index (PCI) method was proposed to evaluate numerical uncertainties in solutions by the Lagrangian particle-based methods. Uncertainties of the numerical solutions due to spatial discretization were calculated. The predicted impact pressures and forces by the present method are in good agreement with experimental data and other published numerical results. The improved higher-order MPS method has also been applied to study fluidstructure interactions (FSI) for an elastic wedge entering calm water. The structural responses of the wedge with a reinforce tip were computed during the water entry. In the present method, different particle spacings and time steps were used for the fluid and the structure. Convergence of solutions on the particle spacings for the fluid and the structure and time step were investigated. Uncertainties of the numerical solutions due to spatial discretization of both the fluid and the structure were evaluated based on the proposed PCI method. Validation studies were carried out to two wedges with deadrise angles of 20ﾟ and 30ﾟ entering water at various velocities. Numerical solutions were compared with the results based on the original higher-order MPS model and the experimental data. The present improved higher-order MPS method led to better agreement with experimental data than the original one, and significantly reduced the oscillations in numerical solutions.

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