Prediction of non-linear wave loads on large floating structures using a 3D numerical wave tank approach

Abstract

In the present work, non-linear wave loads acting on large floating structures are computed using a 3D numerical wave tank (NWT) approach in an approximate manner. The hydrodynamic initial boundary value problem is solved following a Rankine panel-based boundary element method in conjunction with time integration of free-surface constraints and bodymotion equations. To enable long-duration simulation for practical offshore configurations, total velocity potential is split into incident and perturbation part, and the latter effects are linearized. In our earlier works (Ganesan and Sen in J Ocean Eng Mar Energy 1:299-324, 2015; Ganesan and Sen in Appl Ocean Res 51:153-170, 2015), the 2nd order contributions from the linearized perturbation potential were neglected. In this work, we propose a modified formulation for the external load in which the full non-linear loads from the incident wave and up to 2nd order loads from the linear perturbation potential are considered. After presenting some results to validate the present method for steady drift force computations, non-linear loads from the modified formulation are compared with the unmodified form of the method and also with widely used 3D frequency-domain Green-function-based method. Comparative results between these three computations are presented for different geometries and the results are discussed to bring out the relative advantage of the modified formulation in predicting non-linear loads across the range of frequency and wave steepness. Keywords 3D numerical wave tank • Rankine panel method • Direct time domain • Higher order forces • Non-linear wave • Mean drift forces * Shivaji Ganesan T.

Fully nonlinear dynamics of floating solar platform with twin hull by tubular floaters in ocean waves

“…To solve the equation of body motions, various methodologies have been proposed to calculate the instantaneous hydrodynamic pressure on the exact wet surface. An acceleration potential formulation (Vinje and Brevig, 1981) based upon the modal decomposition method can obtain the time derivative of the velocity potential field on the instantaneous wet surface implicitly; for instance Coslovich et al (2021); Ganesan and Sen (2019); Kim and Koo (2019). The implicit body boundary condition algorithm was implemented by Abbasnia and Guedes Soares (2017) to calculate the responses of a ship-shaped freely floating body under strong nonlinear incident waves.…”