Numerical Investigations of a Column Configuration with Towed Super Long Cable in Underwater Environment

In the present study, a simple immersion boundary method was developed to numerically simulate the fluid-structure-acoustic coupling problem of underwater vehicles and their towed super long cables. A typical underwater vehicle connected with different cable models at different positions was created in this study. The length of the vehicle is 4356 mm, the cables are approximately 4 and 6 times the vehicle length, i.e., 17,424 mm and 26,136 mm, and the freestream velocity is 7.72 m/s (15 kts). In the simulation, the freestream velocities are 9.26 m/s (18 kts), 7.72 m/s (15 kts), and 5.14 m/s (10 kts), respectively. The models are numerically simulated by a simple immersion boundary method to solve the flow field structure, the velocity profile, and the transverse flow near the towed cable, compute the pressure pulsation of the cable models with huge lengths and extremely small diameters, and analyze their flow noise. The results show that the towed cables with different lengths have a relatively small impact on the velocity distribution around the underwater vehicle system; however, the transverse flow occurs near the cable, thereby affecting the pressure pulsation changes and causing significant flow noise problems. Furthermore, it was also found that the closer the connection position of the towed cable is to the center position, the more significant the impact on the downstream flow fields and the higher the sound pressure level of the flow noise.