Assessment of the importance of mooring dynamics on the global response of the DeepCwind floating semi-submersible offshore wind turbine

Published: 2013

Author(s):

Masciola, M.
Robertson, A.
Jonkman, J.
Coulling, A. J.
Goupee A. J.

Publication Name: Proceedings of ISOPE 2013, The 23rd International Ocean and Polar Engineering Conference

Publication URL: http://cim.mcgill.ca/~mmascio1/ISOPE2013-TPC-0650.pdf

Research Area:

Offshore Wind & Coastal Resiliency

Keywords:

Floating Offshore Wind, Ocean Engineering, VolturnUS, Wave Energy

Abstract:

This paper studies the influence of mooring line dynamics on the response of a coupled floating offshore wind turbine against an equivalent uncoupled model. The semisubmersible modeled in this paper is based on a design developed by the DeepCwind program and uses the National Renewable Energy Laboratorys (NRELs) 5- megawatt (MW) baseline wind turbine to represent the tower, nacelle, and blade properties. The uncoupled model was formed using FAST, an open-source program that models the wind turbine aerodynamics, control, motion, tower/blade flexure, and wave forces, but with the mooring line forces treated using a quasi-static approximation. In contrast, the coupled model was enabled by pairing FAST with Or- caFlex. OrcaFlex replaces FASTs wave force and quasi-static cable model with an equivalent subsea fluid-structure representation and a lumped-mass cable system to capture the mooring line dynamics. This analysis revealed that an uncoupled model using the quasi-static mooring approximation can underestimate peak mooring line loads versus a coupled model using a dynamic mooring line.