Modelling and Analysis of a Semi-Submersible Wind Turbine With a Central Tower With Emphasis on the Brace System

2013 ◽  
Author(s):  
Chenyu Luan ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Elastic System ◽  
State Of The Art ◽  
Limit State ◽  
Modeling Method ◽  
Ultimate Limit State ◽  
The Novel ◽  
Floating Wind Turbine ◽  
The Time Domain

This paper deals with analysis of the OC4 DeepCWind semi-submersible wind turbine, which is provided by NREL through the OC4 project. This concept is a three-column semi-submersible supporting a 5 MW wind turbine on an additional central column. The fact that the semi-submersible floater needs a large water line restoring moment to achieve sufficient stability and the control of the cost based on the steel weight make the design of braces and pontoons very challenging. Effective methods are needed to check the strength of the brace system based on the response forces and moments in the braces under different design environmental conditions, while the floating wind turbine is needed to be considered as an aero-hydro-servo-elastic system. A novel modeling methodology based on the code Simo/Riflex is introduced in this paper. Simo/Riflex is a state-of-the-art code that can account for the coupling effect between rigid body motions and slender structures (e.g. mooring lines, braces and blades) in the time-domain. Simo/Riflex can be combined with Aerodyn, which is a state-of-the-art aerodynamic code, to model the floating wind turbine as an aero-hydro-servo-elastic system, as well as be combined with simplified aerodynamic codes (e.g.TDHMILL) to improve the efficiency of the numerical simulation. The novel modeling method can give the forces and moments in the brace system of the floater under hydrodynamic and aerodynamic loads in the time-domain. In order to get the structural response of the braces, the side columns and the central supporting column are modeled as independent rigid bodies in Simo while the braces are modeled by beam elements in Riflex. Master and slave relationship is applied at the joints in between of the columns and braces. As an application example, the novel modeling method based on the code Simo/Riflex+TDHMILL, which is capable of modeling the floating wind turbine as an aero-hydro-elastic system, has been used to carry out Ultimate Limit State (ULS) design check for the brace system of the OC4 DeepCWind semi-submersible wind turbine based on relevant standards, i.e. NORSOK N00-3, NORSOK N-004, IEC61400-1, IEC61400-3. The modeling method can also be used by other codes which have similar features as Simo/Riflex.

scholarly journals Mooring System Design and Verification for a Floating Vertical Axis Wind Turbine

2020 ◽  
Vol 11 (03) ◽  
pp. 2050003
Author(s):  
Fausto Raschioni ◽  
Roberto Longo ◽  
Ali Mehmanparast ◽  
Cesare Mario Rizzo
Keyword(s):  
Wind Turbine ◽  
Limit State ◽  
Vertical Axis ◽  
Future Application ◽  
Ultimate Limit State ◽  
Mooring System ◽  
Vertical Axis Wind Turbine ◽  
Floating Wind Turbine ◽  
Crucial Part ◽  
Ultimate Limit

The aim of this study is to investigate the technical feasibility of an innovative vertical axis floating wind turbine concept with the main focus on the design and verification of the mooring system. The study is developed through iterative processes in order to identify the optimum design for the new floating wind turbine concept. The Ultimate Limit State (ULS) criteria have been considered to verify the integrity of the mooring system in the extreme environmental conditions with a 50-year return period. For this purpose, time domain dynamic analysis has been performed using the commercial software OrcaFlex [Orcina website, OrcaFlex software, https://www.orcina.com/ ]. Although the analysis is carried out for a specific site deemed suitable for the project, the results can be used as an input for any future application in other locations. The present study is intended to be a proof of concept with a proposed scientific framework for optimization of the mooring system which is considered to be a crucial part in the design of floating wind turbines due to their complex dynamic behavior.

Comparison of Time and Frequency Domain Simulations of an Offshore Floating Wind Turbine

2011 ◽  
Author(s):  
Maxime Philippe ◽  
Aure´lien Babarit ◽  
Pierre Ferrant
Keyword(s):  
Wind Turbine ◽  
Frequency Domain ◽  
Time Domain ◽  
Degrees Of Freedom ◽  
Domain Model ◽  
Floating Platform ◽  
Floating Wind Turbine ◽  
Non Linear ◽  
Offshore Floating Wind Turbine ◽  
The Time Domain

Time domain simulations of an offshore floating wind turbine have been performed. Hydrodynamic impulse responses of the floating platform are calculated with linear hydrodynamic simulation tool ACHIL3D. A user defined module for the wind turbine design code FAST has been developed to calculate hydrodynamic and mooring loads on the structure. Resolution of the movements of the system is done with FAST. Simulation results in time domain are compared with frequency domain results. In the frequency domain model, the whole system is linearized. In the time domain model, the wind turbine model is not linearized. A good agreement between time and frequency domain calculations is observed, even for the pitch motion. Furthermore we observe a non linearity in the response of sway, roll and yaw degrees of freedom around 0.3 rad.s-1. The effect of viscous damping on the movements of the floating wind turbine system has been studied with the time domain model, and a non linear hydrostatic and Froude-Krylov load model has been developed. Effects of these non linear terms are shown.

Time Domain Coupled Analysis and Load Transfer for Floating Wind Turbine Structures

2018 ◽  
Author(s):  
Kaijia Han ◽  
Torgeir Vada ◽  
QingQing Wang
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Structural Model ◽  
Load Transfer ◽  
Data Transfer ◽  
Coupled Analysis ◽  
Mooring Lines ◽  
Rankine Source ◽  
Floating Wind Turbine ◽  
The Time Domain

A time domain coupled analysis and load transfer for floating wind turbine type structures is demonstrated in this paper. Hydrodynamic coefficients are first sent to a time domain solver for coupled analysis including mooring lines and wind turbine. The wave, motions of the structure and auxiliary forces from mooring lines and wind turbine are sent back to a time domain Rankine source solver to transfer the loads to structural model before the time domain structural analysis and fatigue analysis. A converter program is applied between two solvers to get correct transformations of the wave, motions and forces. Special emphasis has been put on investigation of the consistency of the data transfer. The whole analysis procedure is straightforward and can be applied for other similar structures.

Calibration of a Time-Domain Hydrodynamic Model for A 12 MW Semi-Submersible Floating Wind Turbine

2021 ◽  
Author(s):  
Carlos Eduardo Silva de Souza ◽  
Nuno Fonseca ◽  
Petter Andreas Berthelsen ◽  
Maxime Thys
Keyword(s):  
Numerical Model ◽  
Wind Turbine ◽  
Time Domain ◽  
Quadratic Model ◽  
Wave Loads ◽  
Frequency Wave ◽  
Load Models ◽  
Wave Drift ◽  
Floating Wind Turbine ◽  
Decay Tests

Abstract Design optimization of mooring systems is an important step towards the reduction of costs for the floating wind turbine (FWT) industry. Accurate prediction of slowly-varying horizontal motions is needed, but there are still questions regarding the most adequate models for low-frequency wave excitation, and damping, for typical FWT concepts. To fill this gap, it is fundamental to compare existing load models against model tests results. This paper describes a calibration procedure for a three-columns semi-submersible FWT, based on adjustment of a time-domain numerical model to experimental results in decay tests, and tests in waves. First, the numerical model and underlying assumptions are introduced. The model is then validated against experimental data, such that the adequate load models are chosen and adjusted. In this step, Newman’s approximation is adopted for the second-order wave loads, using wave drift coefficients obtained from the experiments. Calm-water viscous damping is represented as a linear and quadratic model, and adjusted based on decay tests. Additional damping from waves is then adjusted for each sea state, consisting of a combination of a wave drift damping component, and one component with viscous nature. Finally, a parameterization procedure is proposed for generalizing the results to sea states not considered in the tests.

On the Parallelization of a Harmonic Balance Compressible Navier-Stokes Solver for Wind Turbine Aerodynamics

2011 ◽  
Author(s):  
Adrian Jackson ◽  
M. Sergio Campobasso ◽  
Mohammad H. Baba-Ahmadi
Keyword(s):  
Flow Field ◽  
Domain Decomposition ◽  
Wind Turbine ◽  
Time Domain ◽  
Harmonic Balance ◽  
Unsteady Aerodynamics ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Navier Stokes ◽  
The Time Domain

The paper discusses the parallelization of a novel explicit harmonic balance Navier-Stokes solver for wind turbine unsteady aerodynamics. For large three-dimensional problems, the use of a standard MPI parallelization based on the geometric domain decomposition of the physical domain may require an excessive degree of partitioning with respect to that needed when the same aerodynamic analysis is performed with the time-domain solver. This occurrence may penalize the parallel efficiency of the harmonic balance solver due to excessive communication among MPI processes to transfer halo data. In the case of the harmonic balance analysis, the necessity of further grid partitioning may arise because the memory requirement of each block is higher than for the time-domain analysis: it is that of the time-domain analysis multiplied by a variable proportional to the number of complex harmonics used to represent the sought periodic flow field. A hybrid multi-level parallelization paradigm for explicit harmonic balance Navier-Stokes solvers is presented, which makes use of both distributed and shared memory parallelization technologies, and removes the need for further domain decomposition with respect to the case of the time-domain analysis. The discussed parallelization approaches are tested on the multigrid harmonic balance solver being developed by the authors, considering various computational configurations for the CFD analysis of the unsteady flow field past the airfoil of a wind tubine blade in yawed wind.

The Time Domain Analysis of the Flutter of Wind Turbine Blade Combined with Eigenvalue Approach

2013 ◽  
Vol 860-863 ◽  
pp. 342-347
Author(s):  
Hao Wang ◽  
Jiao Jiao Ding ◽  
Bing Ma ◽  
Shuai Bin Li
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Wind Turbine Blade ◽  
Eigenvalue Approach ◽  
Characteristic Roots ◽  
Eigenvalue Method ◽  
The Time Domain

The aeroelasticity and the flutter of the wind turbine blade have been emphasized by related fields. The flutter of the wind turbine blade airfoil and its condition will be focused on. The eigenvalue method and the time domain analysis method will be used to solve the flutter of the wind turbine blade airfoil respectively. The flutter problem will be firstly solved using eigenvalue approach. The flutter region, where the flutter will occur and anti-flutter region, where the flutter will not occur, will be obtained directly by judging the sign of the real part of the characteristic roots of the blade system. Then the time domain analysis of flutter of wind turbine blade will be carried out through the use of the four-order Runge-Kutta numerical methods, the flutter region and the anti-flutter region will be gotten in another way. The time domain analysis can give the changing treads of the aeroelastic responses in great detail than those of the eigenvalue method. The flap displacement of wind turbine blade airfoil will change from convergence to divergence, and change from divergence to convergence extremely suddenly. During the flutter region, the flutter of wind turbine blade will occur extremely dramatically. The flutter region provided by the time domain analysis of the flutter of the blade airfoil accurately coincides with the results of eigenvalue approach, therefore the simulation results are reliable and credible.

Numerical modeling of wind turbine aerodynamic noise in the time domain

2013 ◽  
Vol 133 (2) ◽  
pp. EL94-EL100 ◽  
Author(s):  
Seunghoon Lee ◽  
Seungmin Lee ◽  
Soogab Lee
Keyword(s):  
Numerical Modeling ◽  
Wind Turbine ◽  
Time Domain ◽  
Aerodynamic Noise ◽  
The Time Domain

HYPERCHAOS GENERATED FROM QI SYSTEM AND ITS OBSERVER

2009 ◽  
Vol 23 (07) ◽  
pp. 963-974 ◽  
Author(s):  
XINGYUAN WANG ◽  
YAOXIAN ZHANG ◽  
YONGFENG GAO
Keyword(s):  
Dynamical System ◽  
Time Domain ◽  
Global Exponential Stability ◽  
Observer Design ◽  
The Other ◽  
The Novel ◽  
Nonlinear Controller ◽  
Error System ◽  
The Time Domain ◽  
Lyapunov Exponent Spectrum

This paper reports a novel four-dimensional hyperchaos generated from Qi system, obtained by adding nonlinear controller to Qi chaos system. The novel hyperchaos is studied by bifurcation diagram, Lyapunov exponent spectrum and phase diagram. Numerical simulations show that the new system's behavior can be periodic, chaotic and hyperchaotic as the parameter varies. Based on the time-domain approach, a simple observer for the hyperchaotic is proposed to guarantee the global exponential stability of the resulting error system. The scheme is easy to implement and different from the other observer design since it does not need to transmit all signals of the dynamical system.

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