The paper presents a numerical and experimental investigation on dynamic behaviors of a towed low tension cable. In the numerical study, an implicit finite difference algorithm is employed for threedimensional cable equations. Fluid and geometric non-linearity and bending stiffness are considered and solved by Newton-Raphson iteration. Block tri-diagonal matrix method is applied for the fast calculation of the huge size of matrices. In order to verify the numerical results and to see real physical phenomena, an experiment is carried out for a 6m cable in a deep and long towing tank. The cable is towed in two different ways; one is towed at a constant speed and the other is towed at a constant speed with top end horizontal oscillations. Cable tension and shear forces are measured at the top end. Numerical and experimental results are compared with good agreements in most cases but with some differences in a few cases. The differences are due to drag coefficients caused by vortex shedding. In the numerical modeling, non-uniform element length needs to be employed to cope with the sharp variation of tension and shear forces at near top end.
Cables are extensively used for many ocean applications. Ocean mooring systems, towed acoustic arrays and remotely operated vehicles are just a few of ocean systems that strongly depend on cables. Understanding dynamics of the cable systems is very important for operational and safety aspects. Even if a cable seems to be simple in its shape, the mechanics involved in these problems are very complicated and difficult to solve. Cable problems can be divided into several categories but a primary distinction can be made as a highly tensioned (taut) cable and a lowtension cable. Most researches and applications have been made for taut cables.