Abstract Extreme wave events pose significant risks to offshore structures, necessitating accurate simulation and analysis to ensure structural integrity and safety. This study investigates the hydrodynamic forces on a jacket structure subjected to a focused wave group using the nonlinear potential flow solver OceanWave3D. The extreme wave event within a representative sea state from the North Sea was modelled by a NewWave-type focused wave group. The wave field was validated through forward and backward run consistency checks to ensure numerical robustness. The extracted wave kinematics were employed to calculate hydrodynamic forces on a single vertical cylinder (stick) using the Morison equation, serving as a fundamental case study. The coefficient of variation of the peak force is close to 2x that for the crest elevation. The analysis was extended to an array of cylinders arranged in a single line configuration in both longitudinal and lateral directions with different lateral displacements, representing the structural members of a jacket platform. The average per-stick force on the stick array is consistently smaller and smoother than the forces on individual sticks. Results indicated a linear decrease in the average force as the array moved away from the wave focus location. Furthermore, the peak average force for a line of sticks along the mean wave direction was found to be smaller than that for a line of sticks perpendicular to the mean wave direction, for array centres at the same point. These findings provide valuable insights into the hydrodynamic loading of jacket structures under extreme wave events and highlight the importance of considering wave-structure interactions and array configurations in offshore design and analysis.
Gao et al. (Sun,) studied this question.