Numerical study of secondary load cycle and ringing response on a rounded square column in focused waves

This study investigates secondary load cycle (SLC), reverse slamming force (RSF), and ringing response of a rounded square column subjected to focused waves through numerical simulations. A three-dimensional numerical wave tank is developed using the volume of fluid method to capture the water–air interface. The validity of the numerical method is confirmed by comparing the results with experimental data. Parametric studies are conducted by varying wave steepness, periods, and focus positions to analyze their effects on the SLC and RSF. The results show that both wave steepness and periods significantly influence the amplitudes of the SLC and RSF, and the focus positions have a notable effect on the RSF. Additionally, the study examines the effect of wave focus positions on the structural response, revealing that the dynamic response is most pronounced when the wave is focused at the upstream of the column. Finally, the study analyzed the effects of the SLC and RSF on the ringing response. The results show that both SLC and RSF contribute to the ringing response to varying degrees at different frequency ratios. Notably, within a specific frequency range, the coupled interaction between SLC and RSF produces a stronger ringing response than either component alone. These findings offer valuable insights for the design and analysis of offshore structures under extreme wave conditions.