Dynamic analysis of mooring lines using perturbation techniques

The linearized, two-dimensional equations of the mooring line dynamics are solved using perturbation techniques. It is shown that the solution can be separated into two parts. One represents the near transverse oscillations of the line and is rapidly varying along the length of the cable compared with the static solution, while the other part is slowly varying along the cable length. The two cases of a catenary line and of a neutrally buoyant cable in a strong current are studied in detail. Mooring line terminal impedances are also presented since they can be used for an efficient analysis of the dynamics of a moored structure. Finally the perturbation solution and a direct numerical matrix solution are compared and the range of validity of the asymptotic analysis is discussed.