Computation of Nonlinear Hydrodynamic Loads on Floating Wind Turbines Using Fluid-Impulse Theory: Paper No. OMAE2015-41053

Godine Kok Yan Chan, Paul D. Sclavounos, Jason Jonkman, Gregory Hayman

Research output: Contribution to conferencePaperpeer-review

18 Scopus Citations

Abstract

A hydrodynamics computer module was developed to evaluate the linear and nonlinear loads on floating wind turbines using a new fluid-impulse formulation for coupling with the FAST program. The new formulation allows linear and nonlinear loads on floating bodies to be computed in the time domain. It also avoids the computationally intensive evaluation of temporal and spatial gradients of the velocity potential in the Bernoulli equation and the discretization of the nonlinear free surface. The new hydrodynamics module computes linear and nonlinear loads - including hydrostatic, Froude-Krylov, radiation and diffraction, as well as nonlinear effects known to cause ringing, springing, and slow-drift loads - directly in the time domain. The time-domain Green function is used to solve the linear and nonlinear free-surface problems and efficient methods are derived for its computation. The body instantaneous wetted surface is approximated by a panel mesh and the discretization of the free surface is circumvented by using the Green function. The evaluation of the nonlinear loads is based on explicit expressions derived by the fluid-impulse theory, which can be computed efficiently. Computations are presented of the linear and nonlinear loads on the MIT/NREL tension-leg platform. Comparisons were carried out with frequency-domain linear and second-order methods. Emphasis was placed on modeling accuracy of the magnitude of nonlinear low- and high-frequency wave loads in a sea state. Although fluid-impulse theory is applied to floating wind turbines in this paper, the theory is applicable to other offshore platforms as well.

Original languageAmerican English
Number of pages9
DOIs
StatePublished - 2015
EventASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2015 - St. John's, Canada
Duration: 31 May 20155 Jun 2015

Conference

ConferenceASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2015
Country/TerritoryCanada
CitySt. John's
Period31/05/155/06/15

Bibliographical note

See NREL/CP-5000-63697 for preprint

NREL Publication Number

  • NREL/CP-5000-65599

Other Report Number

  • Paper No. OMAE2015-41053

Keywords

  • Fluid Impulse Theory
  • Wave-structure interactions

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