This paper contributes a method to model the interactions of low-tension cables with the seabed. The cable is modeled as an elastica, and can support tension, torsion and two-axis bending. It is subjected to hydrodynamic forces as well as self-weight, buoyancy, and seabed contact. The seabed is modeled as an elastic foundation with linear damping and prescribed topology. A numerical algorithm is briefly described and then used to simulate cable laying. Several examples are studied including a cable towed in deep water, dropped on an uneven seabed, and finally, towed across an uneven seabed.
Predicting the shape of a cable subjected to hydrodynamic forces has remained a crucial issue in marine and ocean engineering applications. In some applications, cables are laid on the seabed by paying them out from a surface ship and allowing them to fall through the water column. It is important to lay the cables in known regions on the seabed to insure their proper function and survivability. In the particular case of telecommunication cables, knowledge of the cable slack and geometry are very important, because it allows operators to foresee and prevent the formation of tight loops and/or tangles. Loops and tangles are undesirable, because they can potentially kink the cable and block the transmission of signals. These are highly tensioned or "taut" cables, and low-tension cables for which the total tension (dynamic and static) is close to or less than zero. The governing equations for a taut, perfectly flexible, cable need not include the bending and torsional stiffness of the cable, and for the simplest towed cable examples, they can even be solved analytically (Karnoski, 1991). One of the earliest numerical studies was performed by Ablow and Schechter (1983) who provided a code for computing the three-dimensional motion of a towed cable.
