Study on the wave-added thrust and navigational instability risks for a trimaran in stern-quartering seas

As a high-performance multihull vessel, the trimaran offers excellent speed and lateral stability, making it less prone to capsizing in complex sea conditions. When operating in stern-quartering seas, trimarans may benefit from wave–hull interactions that generate negative wave resistance or wave-added thrust (WAT), passively recovering wave energy to enhance forward speed. This mechanism offers a novel approach to improving propulsion efficiency and reducing carbon emissions under specific sea conditions. However, such passively acquired WAT may simultaneously induce unwanted dangerous behaviours (UDBs), including excessive rolling, surf-riding, and broaching. This study employs a hybrid numerical approach coupling the Fully Nonlinear Potential Theory (FNPT) with Computational Fluid Dynamics (CFD) to investigate the seakeeping performance of trimarans under varying initial speeds, wavelengths, and wave heading angles. The research systematically analyzes the effects of wave energy recovery on ship speed and its correlation with navigational stability.