Catenary Mooring Lines with Nonlinear Drag and Touchdown

Abstract

Analytical expressions modeling the tension distribution and geometric deformation along catenary mooring line, including touchdown effect and nonlinear drag, are developed . The motions of a catenary mooring line in the horizontal plane are studied thoroughly. Due to the complexity of the modeling equations, solution can be achieved only by iterative methods. Approximate values for recursion in the solution of the horizontal tension in the catenary are derived based on the first order approximation of the geometric properties of the line. Expressions for the nonlinear drag in the horizontal plane of the catenary are derived based on energy dissipation principles. The resulting analytical expressions serve to calculate the forces in the catenary due to drag in the horizontal plane. The nonlinear drag forces are then recast into a form suitable for mooring applications.