The Dynamic Simulations of the Ship Towing System in Random Waves

In order to investigate the dynamic stability and safety for a ship towing system operated in waves, the present paper develops a nonlinear mathematical model, including seakeeping and maneuvering characteristics, to simulate dynamic behaviors of the towing system in random waves. In addition to waves, wind is also included in the calculations. The time history simulations of six degrees of freedom motion for both the towing and the towed ships are solved by the fourth-order Runge-Kutta method. Because of the waves, the dynamic properties including the towline tension, ship speeds, headings, and distance between two ships are different from those that occur in calm water. The effects of the towpoint's position, towline length, and towing speed on the ship course stability and towline tension are analyzed with respect to different wave and wind headings. In the present study, the suitable operation conditions for the ship towing system are investigated and can be suggested as a reference for improving the stability and safety of towing operation tasks at sea.