Unsteady Simulation of a Bare and Hair-Fairing Underwater Towed Cable System

Exploration devices that are driven or controlled by towing cables play a pivotal role in oceanic exploration efforts. To ensure effective, safe, and precise control of underwater exploration equipment, the hydrodynamic forces affecting the cable components need to be investigated thoroughly. In terms of hydrodynamics, the fluid vortex that occurs behind the towed cable elements introduces complexity that leads to significant variations in drag and lift. In response, several types of towed cables have been proposed, with hair fairing cables emerging as an alternative to bare cables due to their unique shape as well as their inclusion of small hairs that reduce the formation of vortexes. Further, the posture of the cable element occurs at all angles of inclination, thus necessitating simulations that consider the dependence of drag and lift on the inclination angle. The present study addresses these challenges by investigating the forces acting on the cable elements of bare and hair-fairing cables using computational fluid dynamics (CFD). Large Eddy Simulations (LES) are conducted to obtain the hydrodynamic force acting on the cable element at different inclination angles and operating speeds. The CFD calculation results indicate that the hydrodynamic forces acting on the cable elements in the towed cable system depend on the posture of the cable element and the Reynolds number. This study demonstrates the effectiveness of using hair-fairing cable as a replacement for bare cable. The minimized vibration leads to reduced drag and lift acting on the cable element.