Effect of Viscous Drag on Mooring Line Restoring Forces

Abstract

Mooring line is an important component of floating wind turbine and keeps the floating platform in stable position. The mooring lines are subjected to viscous drag forces due to ocean currents. However, the conventional catenary equations used most widely for the analysis of mooring lines does not consider the viscous drag forces due to ocean currents. In this study, a discrete catenary element with the capability of considering viscous drag forces is proposed for analysis of the mooring lines. A nonlinear iterative procedure based on Newton-Raphson method is presented for the mooring line analysis and the influence of drag forces on the mooring line resorting forces is investigated.