Dynamic Model for Catenary Mooring: Experimental Validation of the Wave Induced Load

This note presents a model for the dynamic simulation of a catenary mooring line (or a submarine power cable). In general, mooring lines are subject to a direct wave load (e.g. drag, inertia) in addition to the induced load due to movement of the vessel to which they are linked. Specific aim of this note is to present, calibrate and validate the numerical response to direct wave action, by comparisons with physical model tests. Tests were carried out at the wave flume of the Maritime Laboratory of IMAGE Department, Padova University, within the framework of a Master thesis. Wave induced loads were measured at the fairlead of a compliant chain, with the peculiarity that the fairlead was hinged to a fixed point, the chain being simply subject to the load induced by regular (slightly non-linear) waves. The equations describing the dynamic movements of the chain in Comsol Multiphysics are written in weak form. It is concluded that the model well represents the tests when the drag coefficient is equal to 1.2-1.4 and applied to an area equal to the maximum apparent width.