CFD Simulation of Semi-Submersible Floating Offshore Wind Turbine Under Pitch Decay Motion

2019 ◽  
Author(s):  
Yu Wang ◽  
Hamn-Ching Chen ◽  
Guilherme Vaz ◽  
Simon Burmester
Keyword(s):  
Wind Turbine ◽  
Cfd Simulation ◽  
Flow Characteristics ◽  
Hydrodynamic Pressure ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Natural Period ◽  
Hydrodynamic Damping ◽  
Computational Data ◽  
Computational Fluid Dynamics Cfd

Abstract The application of a computational fluid dynamics (CFD) code to simulate the response of a semi-submersible floating wind turbine under pitch decay motion was investigated in this study. Estimation of the natural period, the hydrodynamic damping and the flow characteristics were the main focus of this study. An extensive verification study of the simulation results was conducted to improve the confidence and reliability of the numerical simulation by the estimation of the numerical errors and uncertainties. The time series of pitch motion was plotted against model test data. In addition, the pitch period and hydrodynamic damping were calculated and compared to experimental data. Detailed flow characteristics as vorticity field and hydrodynamic pressure field on the floater surface were illustrated after post processing of the computational data. The results of the flow characteristics suggest that the heave damping plates were a major contributor to the hydrodynamic damping of this floater in pitch decay.

Verification Study of CFD Simulation of Semi-Submersible Floating Offshore Wind Turbine Under Regular Waves

2021 ◽  
Author(s):  
Yu Wang ◽  
Hamn-Ching Chen ◽  
Guilherme Vaz ◽  
Simon Mewes
Keyword(s):  
Cfd Simulation ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Regular Waves ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Spatial Convergence ◽  
Goal Response ◽  
Computational Fluid Dynamics Cfd ◽  
Response Amplitude Operators

Abstract Utilization of Computational Fluid Dynamics (CFD) codes to perform hydrodynamic analysis of Floating Offshore Wind Turbines (FOWTs) is increasing recently. However, verification studies of the simulations that quantifying numerical uncertainties and permitting a detailed validation in a next phase is often disregarded. In this work, a verification study of CFD simulations of a semi-submersible FOWT design under regular waves is performed. To accomplish this goal, Response Amplitude Operators (RAOs) are derived from the computational results of the heave, surge and pitch motions. Four grids with different grid sizes with a constant refinement ratio are generated for verification of spatial convergence. Three different time increments are paired with each grid for verification of temporal convergence. The verification study is performed by estimation of the numerical errors and uncertainties using procedures proposed by Eca and Hoekstra [1].

Nonlinear Pitch Decay Motion of a Floating Offshore Wind Turbine Structure

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
K. P. Thiagarajan ◽  
R. Urbina ◽  
W. Hsu
Keyword(s):  
Wind Turbine ◽  
Flow Speed ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Natural Period ◽  
Thrust Coefficient ◽  
Pitch Motion ◽  
Blade Element Theory ◽  
Floating Wind Turbine ◽  
Decay Tests

Model tests were conducted on three generic floating wind turbine systems in 2011 and reported in a series of papers at the 31st Ocean, Offshore, and Arctic Engineering Conference in 2012. These tests were conducted at the MARIN facility in The Netherlands, by a consortium of universities, government research organizations, and industry. As part of the testing program, decay tests in platform pitch were conducted with and without wind forcing. It was found that for spar and semisubmersible type structures, resonant pitch motion was damped due to wind in storm sea conditions. The nonlinear decay motion of a floating wind turbine platform is modeled using a one degree-of-freedom nonlinear oscillation equation about a mean offset angle. Attention is paid to the turbine thrust coefficient and its variability with respect to oncoming flow speed, which in turn is affected by the structure pitch motion. The equation of motion reveals that the mean offset position has an important role in the stiffness, damping, and consequently the natural period of pitch motion. Several important dimensionless parameters are introduced. The paper discusses a simple thrust model for an offshore wind turbine (OWT) based on rudiments of blade element theory. Using the simplified thrust coefficient formulation, the increase in platform pitch damping due to wind is formulated. Experimental data reported from prior tests described above show good agreement with the theoretical model.

Nonlinear Pitch Decay of a Floating Offshore Wind Turbine Structure

2013 ◽  
Author(s):  
K. P. Thiagarajan ◽  
R. Urbina ◽  
W. Hsu
Keyword(s):  
Wind Turbine ◽  
Flow Speed ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Natural Period ◽  
Thrust Coefficient ◽  
Pitch Motion ◽  
Blade Element Theory ◽  
Floating Wind Turbine ◽  
Decay Tests

Model tests were conducted on three generic floating wind turbine systems in 2011, and reported in a series of papers at OMAE 2012. These tests were conducted at the MARIN facility in the Netherlands, by a consortium of universities, government research organizations and industry. As part of the testing program, decay tests in platform pitch were conducted with and without wind. It was found that for spar and semi-submersible type structures, resonant pitch motion was damped due to wind in storm sea conditions. The nonlinear decay motion of a floating wind turbine platform is modeled using a one degree-of-freedom nonlinear oscillation equation about a mean offset angle. Attention is paid to the turbine thrust coefficient and its variability with respect to oncoming flow speed, which in turn is affected by the structure pitch motion. The equation of motion reveals that the mean offset position has an important role in the stiffness, damping and consequently the natural period of pitch motion. Several important dimensionless parameters are introduced. The paper discusses a simple thrust model for an offshore wind turbine based on rudiments of blade element theory. Using the simplified thrust coefficient formulation, the increase in platform pitch damping due to wind is formulated. Experimental data reported from prior tests described above show good agreement with the theoretical model.

scholarly journals Generic Upscaling Methodology of a Floating Offshore Wind Turbine

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8490
Author(s):  
Jeffrey Wu ◽  
Moo-Hyun Kim
Keyword(s):  
Wind Turbine ◽  
Center Of Gravity ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Natural Period ◽  
Floating Offshore Wind Turbine ◽  
Floating Base ◽  
Design Changes ◽  
Floating System ◽  
Reference Design

This study presents a generic method to upscale a semi-submersible substructure and tower-nacelle-blade for a floating offshore wind turbine from 5 MW to 15 MW and beyond. The effects of upscaling the column radius and/or distance of the floating base are investigated, and a comparison is made with a 15 MW reference design. It is found that scaling column radius increases the mass of the platform and the heave natural period, while scaling column distance raises the center of gravity and metacentric height of the floating system and slightly decreases the heave natural period. The 15 MW reference design addresses these issues through design changes that increase the ballast mass to lower the center of gravity, and increase the added mass to raise the heave natural period. Finally, a method for estimating the scaling of platform parameters with different assumptions is proposed.

scholarly journals Effect of a Passive Tuned Mass Damper on Offshore Installation of a Wind Turbine Nacelle

2020 ◽  
Author(s):  
Zhiyu Jiang ◽  
Trond Kvia Skrudland ◽  
Madjid Karimirad ◽  
Constatine Machiladies ◽  
Wei Shi
Keyword(s):  
Wind Turbine ◽  
Tuned Mass Damper ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Dynamic Link Library ◽  
Natural Period ◽  
Irregular Wave ◽  
Mass Damper ◽  
Single Mass ◽  
Relative Motions

Abstract Although the installation of offshore wind turbines takes place in calm seas, successful mating of wind turbine components can be challenging due to the relative motions between the two mating parts. This work investigates the effect of a passive tuned mass damper on the mating processes of a nacelle for a 10-megawatt (MW) offshore wind turbine. A nacelle with lifting wires and a monopile with a mass damper are respectively modelled using the multibody formulation in the HAWC2 program. A single mass damper is tuned to target at the first natural period of the monopile and is coupled to the main program using a dynamic link library. Afterwards, numerical simulations were carried out in turbulent wind conditions and irregular wave conditions typical of offshore installation scenarios. Important response variables including the tower-top motions, nacelle motions, and their relative motions are examined in the analysis. By comparing the time series and response statistics, we found that the tower-top motion is more crucial to the installation process than the lifted nacelle motion. For the relative motions and velocities between the nacelle and the tower top, the tuned mass damper can reduce the short-term maximum values by more than 50% for the examined sea states with spectral period between 4 to 12 seconds. This implies that the weather window for marine operations can be expanded if the tuned mass damper is applied.

Integrated FEM and CFD Simulation for Offshore Wind Turbine Structural Response

2019 ◽  
Vol 19 (4) ◽  
pp. 1112-1124 ◽  
Author(s):  
Junwon Seo ◽  
William Schaffer ◽  
Monique Head ◽  
Mehdi Shokouhian ◽  
Eunsoo Choi
Keyword(s):  
Wind Turbine ◽  
Cfd Simulation ◽  
Structural Response ◽  
Offshore Wind ◽  
Offshore Wind Turbine
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