RIASSUNTO
ABSTRACT
In this paper, a fully Lagrangian meshless method is developed to solve the fluid–structure interaction (FSI) problem. The improved Moving Particle Semi-implicit (MPS) method is applied to simulate the incompressible fluid flow, while the Finite Element Method (FEM) is introduced to predict the structure response. The dynamical behavior of the solitary wave and benchmark ship interaction is examined based on the coupled method. Generally, the ship hull is regarded as non-uniform beam mode, which has different cross areas and inertia moments in each node. The variable cross areas and inertia moments can be calculated through present particle method. The structural dynamic response is assumed be to two-dimensional, which means only pitch, heave and vertical bending are considered, while the evolution of free surface and the simulation of wave slamming is three-dimensional. Numerical results illustrate that the coupling MPS-FEM is capable of providing reasonable results for the simulation of violent wave-structure interaction.
INTRODUCTION
Wave-induced motions and structural distortions is one of the important fluid-structure interaction problems in the field of naval architecture and ocean engineering, since its great complexity concerns the violent free surface and nonlinear structural deformation and vibration. On the one hand, for the sea vessels, while encountering extreme conditions, there will be elastic vibration even fatigue damage which would bring the new challenges for the ship security. On the other hand, the wave-induced structural response could exert significant influences on the evolution of free surface.
In traditional seakeeping analysis, the structural responses are predicted considering ship as a rigid body. Many previous studies are mainly focused on the potential flow methods, which present limitations when handling large-amplitude motions, high-speed vessels and other strong nonlinear problems. With the development of computational techniques and numerical methods, computational fluid dynamics (CFD) has experienced great developments in the past decades. Since it is based on more realistic model and takes viscous effects into account, CFD can handle more nonlinear problems and obtain more accurate results than conventional methods did. Hu and Kashiwagi (2004) introduced a nonlinear free surface flow model based on CIP method for handling extremely nonlinear phenomena such as green water impinging on the deck of an advancing ship in waves. Carrica et al. (2007) implemented overset grid method to compute large-amplitude motions of DTMB model 5512 in both medium and high speeds. Shen et al. (2014) employed dynamic overset grid technology to analyze the motion response of KCS model with rotating propeller in head waves based on open-source platform OpenFOAM. Despite the effectiveness, these mesh-based methods may suffer from the difficulties such as the adjustment and regeneration of mesh. However, such difficulties will not occur in meshless method, such as Smoothed Particle Hydrodynamics (SPH; Lucy, 1977) method and Moving Particle Semi-implicit (MPS; Koshizuka and Oka, 1996) method. Recently, some studies have been conducted on implementation of these Lagrangian particle methods into wave-ship interaction. Sueyoshi et al. (2008) simulated the twodimensional wave-induced nonlinear motions of a floating body by MPS method. Shibata (2012) simulated the three-dimensional ship motion with a forward speed under high wave height conditions, and the potential of MPS method as a new simulation tool can be proved.