On the Coupling of Incompressible SPH With a Finite Element Potential Flow Solver for Nonlinear Free Surface Flows

Fourtakas, Georgios (The University of Manchester) | Stansby, Peter K. (The University of Manchester) | Rogers, Benedict D. (The University of Manchester) | Lind, Steven J. (The University of Manchester) | Yan, Shiqiang (School of Engineering and Mathematical Sciences City University of London) | Ma, Qingwei W. (School of Engineering and Mathematical Sciences City University of London)

OnePetro 

ABSTRACT

This paper presents a 2-D one-way coupling methodology between the quasi-arbitrary Lagrange-Euler finite element method (QALE-FEM) (Ma and Yan 2006) which is a nonlinear potential flow solver and incompressible smoothed particle hydrodynamics (ISPH) (Lind et al. 2012), Navier-Stokes equations solver. Nonlinear potential flow solvers such as the QALE-FEM are highly efficient solvers for propagating waves in large domains; however, when extreme nonlinearity takes place such as fragmentation, breaking waves and violent interaction with marine structures, the methodology becomes incapable of dealing with these flow features. A particle method such as ISPH is known to be accurate for such highly nonlinear fragmentized flows with noise-free pressures. ISPH is thus ideal for the near-field and slamming due to its ability to treat highly nonlinear flows and free surface flows with overturning and splashing. Herein, we propose a one-way coupling methodology between QALE-FEM and ISPH where the methods are used for the far field and inner/local regimes respectively. To validate the one-way coupling algorithm a regular wave has been used with satisfactory results. The intention is to extend this approach to strong coupling of the potential flow solver with ISPH using a two-phase (air- water) solver (Lind et al. 2016). The aim is to reliably predict extreme wave forces and slamming on offshore structures such as decks and platforms for marine renewable energy and oil and gas industry.

INTRODUCTION

Structures for offshore oil and gas and more recently for supporting wind turbines and machines for marine renewable energy conversion have been the subject of sustained research and development for a number of years. These offshore structures are often located in depths where waves may be classed as intermediate with breaking bore-like waves which result in extreme loads. However, impulsive loading and slamming due to extreme waves is not well defined particularly when structural response occurs. The problem is complex: important characteristics such as slamming pressures and loads due to breaking wave impact forces involve two or more phases such as air-water, fluid-structure interaction (Lind et al. 2015; Khayyer and Gotoh 2016). As importantly, different scales ranging from the far-field propagation to near-field slamming are significant as highly nonlinear incident waves from the far-field directly determine near-field, possibly breaking wave dynamics (Skillen et al. 2013).