Investigation on wave-body interactions by a coupled High-Order Spectrum method with fully nonlinear Rankine source method

The complex frequency components of ocean waves inherently result in energy transfer during the evolution of wave spectra. This paper introduces a High-order spectrum method coupled with a fully nonlinear hydrodynamic solver (HOS-FNL), for modeling wave-structure interaction within a modulated nonlinear wave train. The approach combines the high-order spectrum method for modeling the incident wave field in a large water domain, with the nonlinear Rankine source method for calculating the disturbed wave field around the floating structure. We validated the HOS code through simulations of free and locked wave cases, and the entire modulation process is analyzed and compared with existing literature. Experimental measurements of the loads acting on a container ship in regular waves are used to validate the core algorithm of the hydrodynamic solver, yielding satisfactory results. Additionally, the behavior of a ship due to finite-amplitude uniform wave train is investigated, visualizing the motion and load response of the ship, wave run-up, diffraction wave patterns, and velocity vectors of the free surface to emphasize the nonlinear characteristics. The HOS-FNL method demonstrates remarkable effectiveness and efficiency, showcasing its potential for a wide range of practical marine applications. •A code named ‘HOS-FNL’ was established to simultaneously predict nonlinear wave-wave and wave-body interactions.•We enable the hydrodynamic solver for mid-calculation using a multi-domain approach and time-asynchronous strategy..•Real-time updates of the nonlinear free and body surfaces provide detailed floating body behavior and wave patterns.•Auxiliary functions independently solve the acceleration potential, preventing numerical instability.•We investigated the impact of Benjamin-Feir instability on a ship in nonlinear wave scenario.