Experimental and Numerical Investigation on Slamming Mechanism of a Mooring Column-Stabilised Semi-Submersible

Semi-submersible offshore platforms play a vital role in deep-sea energy exploitation. However, the vast waves threaten the platform's operation, usually leading to severe consequences. It is essential to study the wave-slamming mechanism of offshore platforms under extreme wave conditions. Existing research usually simplifies the offshore platform slamming problem. This paper establishes a model of a semi-submersible platform and a flexible mooring system in a numerical pool by means of the computational fluid dynamics (CFD) method. The distribution and the sensitivity of the slamming load on columns and deck in waves were investigated, and the model was verified through the basin test. Firstly, based on the Reynolds-averaged Navier-Stokes model, this study considers the volume-of-fluid method to track the free liquid level. After the column and floating body grid are locally refined, the slamming load under extreme regular wave impact is measured by measuring points on the column and deck. Then, the slamming experiment of the semi-submersible was carried out in the basin. The experiment model with a scale ratio of 1:100 was established to investigate the platform's motion and slamming loads under extreme regular and irregular waves. The findings indicate that the slamming load at the junction of the column and deck significantly increased, exhibiting a 'double-peak' phenomenon at the middle of the column. The maximum pressure of slamming at the top of the column demonstrated an inverted U-shaped distribution, with negative pressure occurring after the peak value, indicating a pronounced oscillation effect.