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Title: Investigation of Response Amplitude Operators for Floating Offshore Wind Turbines: Preprint

Abstract

This paper examines the consistency between response amplitude operators (RAOs) computed from WAMIT, a linear frequency-domain tool, to RAOs derived from time-domain computations based on white-noise wave excitation using FAST, a nonlinear aero-hydro-servo-elastic tool. The RAO comparison is first made for a rigid floating wind turbine without wind excitation. The investigation is further extended to examine how these RAOs change for a flexible and operational wind turbine. The RAOs are computed for below-rated, rated, and above-rated wind conditions. The method is applied to a floating wind system composed of the OC3-Hywind spar buoy and NREL 5-MW wind turbine. The responses are compared between FAST and WAMIT to verify the FAST model and to understand the influence of structural flexibility, aerodynamic damping, control actions, and waves on the system responses. The results show that based on the RAO computation procedure implemented, the WAMIT- and FAST-computed RAOs are similar (as expected) for a rigid turbine subjected to waves only. However, WAMIT is unable to model the excitation from a flexible turbine. Further, the presence of aerodynamic damping decreased the platform surge and pitch responses, as computed by both WAMIT and FAST when wind was included. Additionally, the influence of gyroscopic excitation increasedmore » the yaw response, which was captured by both WAMIT and FAST.« less

Authors:
; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy Wind Power Program
OSTI Identifier:
1087800
Report Number(s):
NREL/CP-5000-58098
DOE Contract Number:
AC36-08GO28308
Resource Type:
Conference
Resource Relation:
Conference: To be presented at the 23rd International Ocean, Offshore and Polar Engineering Conference ? ISOPE 2013, 30 June - 5 July 2013, Anchorage, Alaska
Country of Publication:
United States
Language:
English
Subject:
17 WIND ENERGY; FLOATING OFFSHORE WIND TURBINES; OC3-HYWIND SPAR; RESPONSE AMPLITUDE OPERATOR; RAO; Wind Energy

Citation Formats

Ramachandran, G. K. V., Robertson, A., Jonkman, J. M., and Masciola, M. D. Investigation of Response Amplitude Operators for Floating Offshore Wind Turbines: Preprint. United States: N. p., 2013. Web.
Ramachandran, G. K. V., Robertson, A., Jonkman, J. M., & Masciola, M. D. Investigation of Response Amplitude Operators for Floating Offshore Wind Turbines: Preprint. United States.
Ramachandran, G. K. V., Robertson, A., Jonkman, J. M., and Masciola, M. D. Mon . "Investigation of Response Amplitude Operators for Floating Offshore Wind Turbines: Preprint". United States. doi:. https://www.osti.gov/servlets/purl/1087800.
@article{osti_1087800,
title = {Investigation of Response Amplitude Operators for Floating Offshore Wind Turbines: Preprint},
author = {Ramachandran, G. K. V. and Robertson, A. and Jonkman, J. M. and Masciola, M. D.},
abstractNote = {This paper examines the consistency between response amplitude operators (RAOs) computed from WAMIT, a linear frequency-domain tool, to RAOs derived from time-domain computations based on white-noise wave excitation using FAST, a nonlinear aero-hydro-servo-elastic tool. The RAO comparison is first made for a rigid floating wind turbine without wind excitation. The investigation is further extended to examine how these RAOs change for a flexible and operational wind turbine. The RAOs are computed for below-rated, rated, and above-rated wind conditions. The method is applied to a floating wind system composed of the OC3-Hywind spar buoy and NREL 5-MW wind turbine. The responses are compared between FAST and WAMIT to verify the FAST model and to understand the influence of structural flexibility, aerodynamic damping, control actions, and waves on the system responses. The results show that based on the RAO computation procedure implemented, the WAMIT- and FAST-computed RAOs are similar (as expected) for a rigid turbine subjected to waves only. However, WAMIT is unable to model the excitation from a flexible turbine. Further, the presence of aerodynamic damping decreased the platform surge and pitch responses, as computed by both WAMIT and FAST when wind was included. Additionally, the influence of gyroscopic excitation increased the yaw response, which was captured by both WAMIT and FAST.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jul 01 00:00:00 EDT 2013},
month = {Mon Jul 01 00:00:00 EDT 2013}
}

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