A weak-scatterer solution to nonlinear wave-body interaction based on a 3D immersed-boundary adaptive harmonic polynomial cell method

The weak-scatterer (WS) model, introduced by Pawlowski [1], has gained attention for its robustness and stability compared to fully nonlinear potential flow models in studying wave-body interactions. However, its applicability in predicting nonlinear wave loads remains underexplored. This paper integrates the WS formulation into a 3D immersed-boundary adaptive harmonic polynomial cell (IB-AHPC) method, which is an extension of the original HPC method by Shao and Faltinsen [2]. We examine the nonlinear wave diffraction problem of a bottom-mounted vertical circular cylinder in regular waves, comparing WS results with model tests, the FNV theory, and fully nonlinear potential flow solutions. For small wave steepness, the WS model accurately predicts first-, second-, and third-harmonic wave loads, outperforming the FNV model. However, for steeper waves, it significantly overpredicts third-harmonic loads, similar to the FNV model.