Slewing Motion Characteristics of a Towed Ship in Steady Wind

An excessive slewing motion of a towed ship intrudes on sea traffic ways and may lead to the hazardous responses, such as crashing to other vessels or fixed offshore structures. In the presence of wind disturbances, which exerted on an exposed windage areas of a towed ship, her slewing motion behaviour was clearly different as compared with calm water condition. This paper presents a nonlinear analysis of the slewing motion characteristics of towed ship in the steady wind condition. Two different towed ships, one of them equipped with skegs, were towed by a tow ship at the various velocities and the angles of winds. The results revealed that the slewing motion of towed ship (no skeg) was reduced significantly at the angle of wind (θ_w = 120°) in proportion with the increase of wind velocities (U_w). Concurrently, the towed ship has been drift, then preserved its course steadily with a certain heading angle. In addition, the slewing motion of towed ship was also reduced as the increase of ratios of tow point position (l_B/L₂). However, the slewing motions of towed ship raised gradually due to the increase of heading and following wind velocities, which finally led to the course instability.