Development of a fully coupled numerical hydroelasto-plastic approach for offshore structure

Abstract

Offshore structure encountering large waves could generate structural collapsed accident which is a problem of nonlinear fluid–structure interaction sometimes called hydroelasto-plasticity in which structural nonlinearities involving plasticity and buckling and wave load nonlinearities are generated. A viscous-flow numerical approach is put forward to study the hydroelasto-plastic problem in this paper. The viscous-flow hydroelasto-plastic approach combines CFD(Computational Fluid Dynamics) and nonlinear FEM(Finite Element Method) to realize one-way and two-way coupling. CFD platform uses VOF(Volume of Fluid) to models air-wave two-phase flow to make numerical waves which are compared to theory results, and uses DFBI(Dynamic Fluid–Body Interaction) and overlapping grid to calculate offshore structure motion and wave loads. Nonlinear FEM uses explicit nonlinear dynamic FEM to calculate offshore structural collapse responses considering plasticity and buckling. Radial basis function is used to interpolate wave pressures and structural motion and deformation on common surface of hydrodynamic model and FEM model. The viscous-flow hydroelasto-plastic approach is used to simulate an experiment model. Simulation results from both one-way and two-way coupling approaches are compared with experiments. Comparison shows that the two-way coupling provides a better numerical simulation of the experimental model. This paper proposes the viscous-flow hydroelasto-plastic approach coupling CFD and nonlinear FEM as new numerical means to study the offshore structural collapse problem caused by waves.