Numerical Investigation of Green Water Loading on Flexible Structures Using Three-Step CFD-BEM-FEM Approach

Abstract

In this paper, the effect of green water impact on a flexible structure is studied based on three-step computational fluid dynamics (CFD)–boundary element method (BEM)–finite element method (FEM) approach. The impact due to shipping of water on the deck of the vessel is computed using commercial CFD software and used as an external force in coupled BEM-FEM solver. Other hydrodynamic forces such as radiation, diffraction, and Froude-Krylov forces acting on the structure are evaluated using 3D time domain panel method. To capture the structural responses such as bending moment and shear force, 1D finite element method is developed. Moreover, a direct integration scheme based on the Newmark–Beta method is employed to get the structural velocity, displacement, etc., at each time step. To check the effect of the green water impact on the structure, a rectangular barge without forward speed is taken for the analysis. The influence is studied in terms of bending moment, shear force, etc. Results show that the effect of green water impact on the bow region can be severe in extreme seas and lead to various structural damages. Similarly, it is also verified that vessel motion affects green water loading significantly and therefore one must consider its effect while designing a vessel.

Keywords

Green water loading / Computational fluid dynamics / 3D time domain panel method / Finite element method / Newmark–Beta method