Seabed Bathymetry and Friction Modeling in MoorDyn

Stein Housner, Ericka Lozon, Bruce Martin, Dorian Brefort, Matthew Hall

Research output: Contribution to journalArticlepeer-review

2 Scopus Citations


This paper presents the implementation and verification of a seabed bathymetry feature and seabed friction feature to the open-source, lumped-mass mooring system dynamics modeler, MoorDyn, which is part of the National Renewable Energy Laboratory’s aero-hydroservo-elastic simulation tool, OpenFAST. Variations in seabed slope, as well as the frictional effects of mooring lines moving along the seabed, will affect the mooring line tensions of a floating platform and the consequent platform response. These new features are especially relevant for modeling mooring systems in deep-water coastal areas where seabed depth can change significantly over an entire mooring footprint. The bathymetry feature models the seabed as a rectangular grid of variable water depths in place of the existing, uniform water depth in MoorDyn. The friction force is primarily represented as a Coulombic friction force, or the product of a kinetic friction coefficient and the seabed contact normal force, with the ability to differentiate between transverse and axial motion of a line node on the seabed in any bathymetry grid. These capabilities were tested by running MoorDyn and OpenFAST simulations over a variety of seabed and environmental conditions; the resulting fairlead tensions, node tensions, and mooring line kinematics were verified against equivalent OrcaFlex simulations. The results match closely, meaning the features are verified, which will increase the overall fidelity of OpenFAST and FAST.Farm simulations.

Original languageAmerican English
Article numberArticle No. 012018
Number of pages10
JournalJournal of Physics: Conference Series
Issue number1
StatePublished - 2022
Event19th EERA DeepWind Offshore Wind R and D Conference, DeepWind 2022 - Trondheim, Norway
Duration: 19 Jan 202221 Jan 2022

Bibliographical note

Publisher Copyright:
© 2022 Institute of Physics Publishing. All rights reserved.

NREL Publication Number

  • NREL/JA-5000-82033


  • bathymetry
  • floating offshore wind
  • friction
  • mooring modeling


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