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Summary of Conclusions and Recommendations Drawn from the DeepCWind Scaled Floating Offshore Wind System Test Campaign: Preprint

Description: The DeepCwind consortium is a group of universities, national labs, and companies funded under a research initiative by the U.S. Department of Energy (DOE) to support the research and development of floating offshore wind power. The two main objectives of the project are to better understand the complex dynamic behavior of floating offshore wind systems and to create experimental data for use in validating the tools used in modeling these systems. In support of these objectives, the DeepCwind c… more
Date: July 1, 2013
Creator: Robertson, A. N.; Jonkman, J. M.; Masciola, M. D.; Molta, P.; Goupee, A. J.; Coulling, A. J. et al.
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Partner: UNT Libraries Government Documents Department
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New Structural-Dynamics Module for Offshore Multimember Substructures within the Wind Turbine Computer-Aided Engineering Tool FAST: Preprint

Description: FAST, developed by the National Renewable Energy Laboratory (NREL), is a computer-aided engineering (CAE) tool for aero-hydro-servo-elastic analysis of land-based and offshore wind turbines. This paper discusses recent upgrades made to FAST to enable loads simulations of offshore wind turbines with fixed-bottom, multimember support structures (e.g., jackets and tripods, which are commonly used in transitional-depth waters). The main theory and strategies for the implementation of the multimembe… more
Date: August 1, 2013
Creator: Song, H.; Damiani, R.; Robertson, A. & Jonkman, J.
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Partner: UNT Libraries Government Documents Department
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Assessing Fatigue and Ultimate Load Uncertainty in Floating Offshore Wind Turbines Due to Varying Simulation Length

Description: With the push towards siting wind turbines farther offshore due to higher wind quality and less visibility, floating offshore wind turbines, which can be located in deep water, are becoming an economically attractive option. The International Electrotechnical Commission's (IEC) 61400-3 design standard covers fixed-bottom offshore wind turbines, but there are a number of new research questions that need to be answered to modify these standards so that they are applicable to floating wind turbine… more
Date: July 1, 2013
Creator: Stewart, G.; Lackner, M.; Haid, L.; Matha, D.; Jonkman, J. & Robertson, A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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State-Space Realization of the Wave-Radiation Force within FAST: Preprint

Description: Several methods have been proposed in the literature to find a state-space model for the wave-radiation forces. In this paper, four methods were compared, two in the frequency domain and two in the time domain. The frequency-response function and the impulse response of the resulting state-space models were compared against the ones derived by the numerical code WAMIT. The implementation of the state-space module within the FAST offshore wind turbine computer-aided engineering (CAE) tool was ve… more
Date: June 1, 2013
Creator: Duarte, T.; Sarmento, A.; Alves, M. & Jonkman, J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Hybrid Electro-Mechanical Simulation Tool for Wind Turbine Generators: Preprint

Description: This paper describes the use of MATLAB/Simulink to simulate the electrical and grid-related aspects of a WTG and the FAST aero-elastic wind turbine code to simulate the aerodynamic and mechanical aspects of the WTG. The combination of the two enables studies involving both electrical and mechanical aspects of the WTG.
Date: May 1, 2013
Creator: Singh, M.; Muljadi, E. & Jonkman, J.
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Partner: UNT Libraries Government Documents Department
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Importance of Second-Order Difference-Frequency Wave-Diffraction Forces in the Validation of a Fast Semi-Submersible Floating Wind Turbine Model: Preprint

Description: To better access the abundant offshore wind resource, efforts across the world are being undertaken to develop and improve floating offshore wind turbine technologies. A critical aspect of creating reliable, mature floating wind turbine technology is the development, verification, and validation of efficient computer-aided-engineering (CAE) tools that can be relied upon in the design process. The National Renewable Energy Laboratory (NREL) has created a comprehensive, coupled analysis CAE tool … more
Date: June 1, 2013
Creator: Couling, A. J.; Goupee, A. J.; Robertson, A. N. & Jonkman, J. M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Numerical Prediction of Experimentally Observed Behavior of a Scale Model of an Offshore Wind Turbine Supported by a Tension-Leg Platform: Preprint

Description: Realizing the critical importance the role physical experimental tests play in understanding the dynamics of floating offshore wind turbines, the DeepCwind consortium conducted a one-fiftieth-scale model test program where several floating wind platforms were subjected to a variety of wind and wave loading condition at the Maritime Research Institute Netherlands wave basin. This paper describes the observed behavior of a tension-leg platform, one of three platforms tested, and the systematic ef… more
Date: January 1, 2013
Creator: Prowell, I.; Robertson, A.; Jonkman, J.; Stewart, G. M. & Goupee, A. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Investigation of Response Amplitude Operators for Floating Offshore Wind Turbines: Preprint

Description: 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 compute… more
Date: July 1, 2013
Creator: Ramachandran, G. K. V.; Robertson, A.; Jonkman, J. M. & Masciola, M. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Building and Calibration of a FAST Model of the SWAY Prototype Floating Wind Turbine: Preprint

Description: Present efforts to verify and validate aero-hydro-servo-elastic numerical simulation tools that predict the dynamic response of a floating offshore wind turbine are primarily limited to code-to-code comparisons or code-to-data comparisons using data from wind-wave basin tests. In partnership with SWAY AS, the National Renewable Energy Laboratory (NREL) installed scientific wind, wave, and motion measurement equipment on the 1/6.5th-scale prototype SWAY floating wind system to collect data to va… more
Date: September 1, 2013
Creator: Koh, J. H.; Robertson, A.; Jonkman, J.; Driscoll, F. & Ng, E. Y. K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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New Modularization Framework for the FAST Wind Turbine CAE Tool: Preprint

Description: NREL has recently put considerable effort into improving the overall modularity of its FAST wind turbine aero-hydro-servo-elastic tool to (1) improve the ability to read, implement, and maintain source code; (2) increase module sharing and shared code development across the wind community; (3) improve numerical performance and robustness; and (4) greatly enhance flexibility and expandability to enable further developments of functionality without the need to recode established modules. The new … more
Date: January 1, 2013
Creator: Jonkman, J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Numerical Stability and Accuracy of Temporally Coupled Multi-Physics Modules in Wind-Turbine CAE Tools

Description: In this paper we examine the stability and accuracy of numerical algorithms for coupling time-dependent multi-physics modules relevant to computer-aided engineering (CAE) of wind turbines. This work is motivated by an in-progress major revision of FAST, the National Renewable Energy Laboratory's (NREL's) premier aero-elastic CAE simulation tool. We employ two simple examples as test systems, while algorithm descriptions are kept general. Coupled-system governing equations are framed in monolith… more
Date: February 1, 2013
Creator: Gasmi, A.; Sprague, M. A.; Jonkman, J. M. & Jones, W. B.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Incorporation of Multi-Member Substructure Capabilities in FAST for Analysis of Offshore Wind Turbines: Preprint

Description: FAST, developed by the National Renewable Energy Laboratory (NREL), is an aero-hydro-servo-elastic tool widely used for analyzing onshore and offshore wind turbines. This paper discusses recent modifications made to FAST to enable the examination of offshore wind turbines with fixed-bottom, multi-member support structures (which are commonly used in transitional-depth waters).; This paper addresses the methods used for incorporating the hydrostatic and hydrodynamic loading on multi-member struc… more
Date: May 1, 2012
Creator: Song, H.; Robertson, A.; Jonkman, J. & Sewell, D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Assessing the Importance of Nonlinearities in the Development of a Substructure Model for the Wind Turbine CAE Tool FAST: Preprint

Description: Design and analysis of wind turbines are performed using aero-servo-elastic tools that account for the nonlinear coupling between aerodynamics, controls, and structural response. The NREL-developed computer-aided engineering (CAE) tool FAST also resolves the hydrodynamics of fixed-bottom structures and floating platforms for offshore wind applications. This paper outlines the implementation of a structural-dynamics module (SubDyn) for offshore wind turbines with space-frame substructures into t… more
Date: March 1, 2013
Creator: Damiani, R.; Jonkman, J.; Robertson, A. & Song, H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Effect of Second-Order Hydrodynamics on Floating Offshore Wind Turbines: Preprint

Description: Offshore winds are generally stronger and more consistent than winds on land, making the offshore environment attractive for wind energy development. A large part of the offshore wind resource is however located in deep water, where floating turbines are the only economical way of harvesting the energy. The design of offshore floating wind turbines relies on the use of modeling tools that can simulate the entire coupled system behavior. At present, most of these tools include only first-order h… more
Date: July 1, 2013
Creator: Roald, L.; Jonkman, J.; Robertson, A, & Chokani, N.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Calibration and Validation of a Spar-Type Floating Offshore Wind Turbine Model using the FAST Dynamic Simulation Tool: Preprint

Description: In 2007, the FAST wind turbine simulation tool, developed and maintained by the U.S. Department of Energy's (DOE's) National Renewable Energy Laboratory (NREL), was expanded to include capabilities that are suitable for modeling floating offshore wind turbines. In an effort to validate FAST and other offshore wind energy modeling tools, DOE funded the DeepCwind project that tested three prototype floating wind turbines at 1/50th scale in a wave basin, including a semisubmersible, a tension-leg … more
Date: November 1, 2012
Creator: Browning, J. R.; Jonkman, J.; Robertson, A. & Goupee, A. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Simulation-Length Requirements in the Loads Analysis of Offshore Floating Wind Turbines: Preprint

Description: The goal of this paper is to examine the appropriate length of a floating offshore wind turbine (FOWT) simulation - a fundamental question that needs to be answered to develop design requirements. To examine this issue, a loads analysis of an example FOWT was performed in FAST with varying simulation lengths. The offshore wind system used was the OC3-Hywind spar buoy, which was developed for use in the International Energy Agency Code Comparison Collaborative Project and supports NREL's offshor… more
Date: June 1, 2013
Creator: Haid, L.; Stewart, G.; Jonkman, J.; Robertson, A.; Lackner, M. & Matha, D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Offshore Code Comparison Collaboration (OC3) for IEA Wind Task 23 Offshore Wind Technology and Deployment

Description: This final report for IEA Wind Task 23, Offshore Wind Energy Technology and Deployment, is made up of two separate reports, Subtask 1: Experience with Critical Deployment Issues and Subtask 2: Offshore Code Comparison Collaborative (OC3). Subtask 1 discusses ecological issues and regulation, electrical system integration, external conditions, and key conclusions for Subtask 1. Subtask 2 included here, is the larger of the two volumes and contains five chapters that cover background information … more
Date: December 1, 2010
Creator: Jonkman, J. & Musial, W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Atmospheric and Wake Turbulence Impacts on Wind Turbine Fatigue Loading: Preprint

Description: Large-eddy simulations of atmospheric boundary layers under various stability and surface roughness conditions are performed to investigate the turbulence impact on wind turbines. In particular, the aeroelastic responses of the turbines are studied to characterize the fatigue loading of the turbulence present in the boundary layer and in the wake of the turbines. Two utility-scale 5 MW turbines that are separated by seven rotor diameters are placed in a 3 km by 3 km by 1 km domain. They are sub… more
Date: December 1, 2011
Creator: Lee, S.; Churchfield, M.; Moriarty, P.; Jonkman, J. & Michalakes, J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Offshore Code Comparison Collaboration Continuation (OC4), Phase I - Results of Coupled Simulations of an Offshore Wind Turbine with Jacket Support Structure: Preprint

Description: This paper presents the results of the IEA Wind Task 30, Offshore Code Comparison Collaboration Continuation Project - Phase 1.
Date: March 1, 2012
Creator: Popko, W.; Vorpahl, F.; Zuga, A.; Kohlmeier, M.; Jonkman, J.; Robertson, A. et al.
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Partner: UNT Libraries Government Documents Department
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Inverse Load Calculation of Wind Turbine Support Structures - A Numerical Verification Using the Comprehensive Simulation Code FAST: Preprint (Revised)

Description: Physically measuring the dynamic responses of wind turbine support structures enables the calculation of the applied loads using an inverse procedure. In this process, inverse means deriving the inputs/forces from the outputs/responses. This paper presents results of a numerical verification of such an inverse load calculation. For this verification, the comprehensive simulation code FAST is used. FAST accounts for the coupled dynamics of wind inflow, aerodynamics, elasticity and turbine contro… more
Date: November 1, 2012
Creator: Pahn, T.; Jonkman, J.; Rolges, R. & Robertson, A.
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Partner: UNT Libraries Government Documents Department
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Challenges in Simulation of Aerodynamics, Hydrodynamics, and Mooring-Line Dynamics of Floating Offshore Wind Turbines

Description: This paper presents the current major modeling challenges for floating offshore wind turbine design tools and describes aerodynamic and hydrodynamic effects due to rotor and platform motions and usage of non-slender support structures.
Date: October 1, 2011
Creator: Matha, D.; Schlipf, M.; Cordle, A.; Pereira, R. & Jonkman, J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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FAST Code Verification of Scaling Laws for DeepCwind Floating Wind System Tests: Preprint

Description: This paper investigates scaling laws that were adopted for the DeepCwind project for testing three different floating wind systems at 1/50 scale in a wave tank under combined wind and wave loading.
Date: April 1, 2012
Creator: Jain, A.; Robertson, A. N.; Jonkman, J. M.; Goupee, A. J.; Kimball, R. W. & Swift, A. H. P.
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Partner: UNT Libraries Government Documents Department
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