THE UNDERWATER TOWED SYSTEM BEHAVIOR DURING SHIP TURNING MANEUVERS

The depth and attitude of underwater towed system show complex behavior during the towing ship turning maneuvers. However, it remains unclear how the two indexes change when the coupling relationship between the cable and the towed vehicle is considered. Here, to solve this issue, and we develop a new numerical method that can be used to predict the behavior of towed system during towing ship turning maneuvers. Specially, a finite difference method and six-degree-of-freedom equations are used to describe the motion of towed cable and towed vehicle respectively. Based on the center finite difference method, the partial differential equations and differential equations are transformed to nonlinear algebra equations then the Newton iteration method is used to solve the nonlinear equations. Then, we simulate the transient behaviors of towed system during the towing ship making 180 and 360 with different turning radius, and find that the depth and attitude of towed system are affected by the towing ship turning maneuvers. We show that the smaller of the turning radius, the variations of depth and attitude are larger. Moreover, the new steady state can be achieved easily during the 360 turning maneuver. The numerical method and result that we derived can be applied to design the towing ship turning maneuvers, towed system and control method.