Study on dynamic response of underwater towed system in ship propeller wakes using a new hydrodynamic model

The dynamic analysis of underwater towed systems is challenging considering complex flow disturbances such as ship propeller wakes. This paper proposed a new fully-coupled three-dimensional hydrodynamic model for the dynamic analysis of an underwater towed system under complex flow disturbances. The hydrodynamic char-acteristics of the towed vehicle and the flow field behind the towing ship and propeller were simulated using computational fluid dynamics (CFD). The fluid forces on the towing cable were determined by combining the Morison formula and the CFD method. A dynamic analysis of an underwater towed system in a towing ship propeller wake under typical uncontrolled towing and depth regulation operations was conducted. The simu-lation results indicated that the proposed method was reasonable. Moreover, the time-averaged position and posture of the underwater towed system and its hydrodynamic characteristics vary with the rotation rate of the ship propeller in uncontrolled towing operation under a fixed towing speed. Furthermore, the fluid forces on the towing system and the cable tension in the depth regulation operation changed more drastically than in the uncontrolled towing operation. The proposed method can be easily extended to simulate other marine cable systems.