As the size of liquid cargo ship enlarges, the hydro-elastic behavior induced by the sloshing flow should be taken into account for the design of a safer tank. In this paper, the response of elastic tank walls induced by the sloshing impact loads is numerically investigated. The in-house solver MLParticle-SJTU, which is developed base on the Moving Particle Semi-Implicit (MPS) method for fluid analysis and expanded with the finite element method (FEM) for structure analysis, is employed for the simulation. The coupling strategy between the fluid and structural analysis modules of the solver, together with the data transformation on the interface, are introduced in detail. Behaviors of the elastic tank walls under the impulsive forces of sloshing flow with high filling ratio of water are simulated and characteristics regarding the roof impact event, including the evolutions of free surface, dynamic responses of the structures in both time and frequency domains, are presented.
In the past decades, the sloshing flow in partially filled tanks of liquid cargo ship has been studied intensively. Most contributions are focused on the extreme impact pressures on the tank walls, the coupling mechanism between ship motions and internal sloshing flows (Zhao et al., 2014; Mitra et al., 2012), techniques to minimize the sloshing (Liu and Lin, 2009) in rigid tanks with model scale, etc. In these works, the assumption that the tank walls are rigid structures is justified while the size of tank is relatively small. Actually, the resonance frequency of fluid motion in cargo tanks would decrease to the same order of the ship motion frequency as the size of ship enlarges, which may result in structural deformation or even serious damage (Lee and Choi, 1999). Hence, the elasticity of tank walls should be taken into account for the design of a larger and safer tank.
Until now, numerical approach is more popular in investigating the fluid structure interaction (FSI) problem of sloshing involving tank's deformation in comparison with the experimental method which is expensive and limited in scope and theoretical analysis method which is difficult to describe the violent free surface evolution. For the FSI problem in an oil/water tank, deformation of the whole tank wall results from the impact loads of sloshing flow is dominant. To investigate the relevance between the structural oscillation and impact pressure patterns, many numerical approaches are proposed. For instance, Lee et al. (1995) utilized a finite element (FE) method coupled with compressible finite volume method (FVM) to analyze the structure and sloshing fluid behaviors in a tank of VLCC. Fossa et al. (2012) investigated the possible effects of a deformable structure on the sloshing phenomenon with the help of ADINA software which is based on the finite element method (FEM) for both fluid and structural analysis. Liao and Hu (2013) developed a coupling finite difference method (FDM) and the finite element method (FEM) for simulating the interaction between liquid sloshing flow in a rolling tank and a thin elastic plate. However, applications of these grid-based methods face some challenges, e.g. inefficient process of grids generation for complex shape of structure, requirement of dynamic mesh technologies for moving boundary or large structural deformation, simulation of free surface with large deformation or breaking, etc. In view of these points, the Lagrangian meshless methods, which are the new generation computational methods, are quite suitable to tackle these challenges. For example, the Moving Particle Semi-Implicit (MPS) method, which is originally proposed by Koshizuka and Oka (1996) for incompressible flow, has been integrated with the FEM and exhibits good performance in FSI problem according to the numerical benchmark tests of dam break flow interacting with flexible structure (Mitsume et al., 2014; Sun et al., 2015). However, the application of the MPS-FEM coupled method for the interaction between violent sloshing flow and elastic tank is rarely reported.
