scholarly journals Estimation of Seismic Load Demand for a Wind Turbine in the Time Domain: Preprint

2010 ◽  
Author(s):  
I. Prowell ◽  
A. Elgamal ◽  
C. Uang ◽  
J. Jonkman
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Seismic Load ◽  
Load Demand ◽  
The Time Domain

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

scholarly journals Aeroelastic stability of idling wind turbines

2017 ◽  
Vol 2 (2) ◽  
pp. 415-437 ◽  
Author(s):  
Kai Wang ◽  
Vasilis A. Riziotis ◽  
Spyros G. Voutsinas
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Operation Mode ◽  
Nonlinear Effects ◽  
Eigenvalue Stability ◽  
Out Of Plane ◽  
Aeroelastic Simulations ◽  
The Time Domain ◽  
Work Done ◽  
Nonlinear Time Domain

Abstract. Wind turbine rotors in idling operation mode can experience high angles of attack within the post-stall region that are capable of triggering stall-induced vibrations. The aim of the present paper is to extend the existing knowledge on the dynamics and aerodynamics of an idling wind turbine and characterize its stability. Rotor stability in slow idling operation is assessed on the basis of nonlinear time domain and linear eigenvalue analyses. The aim is to establish when linear analysis is reliable and identify cases for which nonlinear effects are significant. Analysis is performed for a 10 MW conceptual wind turbine designed by DTU. First, the flow conditions that are likely to favor stall-induced instabilities are identified through nonlinear time domain aeroelastic simulations. Next, for the above specified conditions, eigenvalue stability analysis is performed to identify the low damped modes of the turbine. The eigenvalue stability results are evaluated through computations of the work done by the aerodynamic forces under imposed harmonic motion following the shape and frequency of the various modes. Nonlinear work characteristics predicted by the ONERA and Beddoes–Leishman (BL) dynamic stall models are compared. Both the eigenvalue and work analyses indicate that the asymmetric and symmetric out-of-plane modes have the lowest damping. The results of the eigenvalue analysis agree well with those of the nonlinear work analysis and the time domain simulations.

A Complex Frequency Domain Model of Wind Turbine Structures

1995 ◽  
Vol 117 (4) ◽  
pp. 311-317 ◽  
Author(s):  
P. So̸rensen ◽  
G. C. Larsen ◽  
C. J. Christensen
Keyword(s):  
Wind Turbine ◽  
Frequency Domain ◽  
Time Domain ◽  
Domain Model ◽  
Horizontal Axis ◽  
Complex Frequency ◽  
Horizontal Axis Wind Turbine ◽  
The Time Domain

The present paper describes a frequency domain model of the structure of an operating horizontal axis wind turbine with three or more blades. The frequency domain model is implemented along with an analogous time domain model in a PC code. This PC code is used to verify the frequency domain model comparing loads on the structure calculated with the frequency domain model both to loads calculated with the time domain model and to measured loads.

scholarly journals Transient Response Estimation of an Offshore Wind Turbine Support System

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 891 ◽  
Author(s):  
Fushun Liu ◽  
Xingguo Li ◽  
Zhe Tian ◽  
Jianhua Zhang ◽  
Bin Wang
Keyword(s):  
Wind Turbine ◽  
Frequency Domain ◽  
Transient Response ◽  
Time Domain ◽  
Initial Conditions ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Domain Method ◽  
The Time Domain ◽  
External Loads

To obtain reliable estimations of the dynamic responses of high-rising marine structures such as offshore wind turbines with obvious nonzero initial conditions, traditional frequency-domain methods cannot be employed because they provide only steady-state results. A novel frequency-domain transient response estimation method for offshore wind turbines is presented in this paper. This method builds upon a recent, significant theoretical development, which found that expressions of external loads in the frequency domain can be obtained by discretizing their eigenvalues and corresponding complex coefficients rather than directly by discrete Fourier transform (DFT) analysis, which makes it possible to deal with nonzero conditions in the frequency domain. One engineering advantage of this approach is its computational efficiency, as the motion equations of the system can be solved in the frequency domain. In order to demonstrate this approach, a case of a monopile-supported wind turbine with nonzero initial conditions was investigated. The numerical results indicate that the approach matches well with the time-domain method, except for a small, earlier portion of the estimated responses. A second case study of a sophisticated, jacket support wind turbine, involving practical issues such as complex external loads and computation efficiency, is also discussed, and comparisons of the results with the time-domain method and traditional frequency-domain method using the commercial software ANSYS are included here.

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.

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 A New Elastoplastic Time-History Analysis Method for Frame Structures

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Qianqian Liang ◽  
Chen Zhao ◽  
Jun Hu
Keyword(s):  
Periodic Point ◽  
Time Domain ◽  
Response Spectrum ◽  
Time History ◽  
Specific Yield ◽  
Seismic Load ◽  
Structural Systems ◽  
History Analysis ◽  
The Time Domain ◽  
Fracture Stiffness

This study aimed to analyze the formation and application of the time-domain elastoplastic response spectrum. The elastoplastic response spectrum in the time domain was computed according to the trilinear force-restoring model. The time-domain elastoplastic response spectrum corresponded to a specific yield strength coefficient, fracture stiffness, and yield stiffness. However, the force-restoring models corresponding to different structural systems and the states of the structural systems at different moments were not the same. Therefore, the dynamic characteristics of a particular periodic point corresponding to a particular structure were meaningful for the elastoplastic response spectrum. In addition, the curve in the time-domain dimension along the periodic point truly reflected the real-time response of the structure when the structure encountered a seismic load.

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