Abstract:As marine aquaculture expands from coastal regions to the deep seas, large-scale semi-submersible aquaculture platforms have become the primary engineering equipment in recent years because of their high stability and ease of installation. To reduce the difficulty of offshore construction, these platforms are typically installed on land and towed to the operating areas by tugboats. However, owing to the high center of gravity of the platform, there is a risk of capsizing during long-distance towing. In this study, a numerical analysis model was developed to assess the hydrodynamic performance of an aquaculture platform, including its frame and net, during wet-towing transportation. For a large-scale frame, including pontoons and columns, a three-dimensional potential flow theory was applied to solve the diffraction and radiation problems. For the thin net, a semi-empirical Morison equation was used to calculate the wave loads and a mesh group method was implemented to decrease the computational cost and time. The motion equation was solved in the time domain using the impulsive response function method, and analysis of nonlinear catenary towline was performed using the lumped-mass method. This model examines the impact of significant wave height, wave direction, towing speed, towline length, and mooring point position on the motion response and towline tension of a semi-submersible aquaculture platform. The results indicate that as the significant wave height rises from 1.25 m to 4.00 m, the heave acceleration and pitch angle of the aquaculture platform increase by 293% and 750%, respectively, whereas the towline tension increases by 358%. The aquaculture platform experienced more severe pitch motion in the following waves than in the head waves although the towline tension decreased. Furthermore, increasing the towing speed from 2.0 kn to 5.0 kn leads to a 56% reduction in heave acceleration and an 112% increase in towline tension. Tripling the towline length results in a 43% decrease in the pitch angle and 31% decrease in the towline tension. The height of the towing point has a significant impact on the pitch motion. For practical engineering applications, it is recommended to limit the maximum sea condition for towing aquaculture platforms to level 4, keep the towing speed below 5.0 kn, avoid towing in following waves, and instead opt for quarter head waves. Additionally, appropriately increasing the tow line length can improve the towing stability.