This paper presents recent offshore applications of the SWENSE (Spectral Wave Explicit Navier-Stokes Equations) approach which is an original solution scheme for the time simulation of wave-body interactions using a combined potential / RANSE approach and a decomposition of the nonlinear flow in incident and diffracted parts. The viscous free surface flow around an TLP is computed in cases of regular and irregular waves. The incoming regular wave field is given by an algorithm based on stream function theory (Rienecker & Fenton, 1981) while the incoming irregular wave field is computed by a Higher Order Spectral (HOS) model (Bonnefoy et al, 2004). This latter model is validated against the previous one for a case of regular waves. Concerning results on the TLP structure, time histories of free surface elevations and pressure loads are compared to results from a time domain nonlinear potential flow solver (Ferrant, 1996; Ferrant et al, 2003b). Results obtained with the SWENSE method show an overall good agreement with second order potential flow results. Essential non linear effects associated with the interaction with the free surface are captured, while noticeable viscous effects are also observed, in the form of vortices shed by pontoons corners. More in-depth comparisons with experimental or numerical data have to be undertaken but these preliminary results are a good indication of the capacity of the SWENSE scheme for simulating wave-body interactions in the offshore context.

INTRODUCTION

The present paper is devoted to recent developments of an original solution scheme for the time accurate simulation of wave body interactions using a combined potential/RANSE approach. In this scheme named SWENSE (Spectral Wave Explicit Navier-Stokes Equations), the undisturbed incident wave field is modeled using fully nonlinear potential flow theory, while the nonlinear diffracted flow is simulated using a modified Navier-Stokes solver.

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