Gyroscopic Effects of Horizontal Axis Wind Turbines Using Stochastic Aeroelasticity via Spinning Finite Elements

2012 ◽  
Author(s):  
Antonio Velazquez ◽  
R. Andrew Swartz
Keyword(s):  
Wind Turbine ◽  
Dynamic Condition ◽  
The Body ◽  
Horizontal Axis ◽  
Rotor Blades ◽  
Mathematical Framework ◽  
Horizontal Axis Wind Turbine ◽  
Study Results ◽  
Out Of Plane ◽  
Gyroscopic Effects

Horizontal axis wind turbine (HAWTs) structures, throughout the years, have presumed to be of relatively simple construction, but wind-induced aerodynamic vibrations, wind-field conditions, and power requirements tend to lead to the need for increasingly complicated designs. One phenomenon that requires special attention is the gyroscopic or Coriolis effect. In general, blades design codes are written to optimize for lightness and slenderness, but also to withstand excitations at high frequency. As a result, gyroscopic motion derives as a nonlinear dynamic condition in the out-of-plane direction that is difficult to characterize by means of the well-known vibrational theory that has been established for their design and analysis. The present study develops and presents a probabilistic analysis of the precession — gyroscopic — effects of a wind turbine model developed for tapered-swept cross-sections of nt degree with nonlinear variations of mass and geometry along the body of the blade. A dynamic orthogonal decoupling method is utilized to successfully perform the aeroelastic analysis by decoupling the damped-gyroscopic equations of motion, as a result of the addition of Rayleigh damping — symmetric proportional mass and stiffness — within the linear system in study. Results are valid for yaw-free rotor configurations by means of unknown and random (though bounded) yaw rates. Simultaneously, those results can easily be expanded for yaw-controlled mechanisms. The yaw-free assumption presents a higher risk of potential reliability expectations, given the stochastic impairment of the gyroscopic nature that is present for out-of-plane axis motions, requiring special attention at higher frequencies. This impairment becomes particularly troublesome for blade profiles with tapered-swept cross-section variations. This uncertainty can be minimized by incorporating a mathematical framework capable of characterizing properly the yaw action such that gyroscopic effects can be fully interpreted and diagnosed. In summary, the main goal is to decipher the complexity of gyroscopic patterns of flexible rotor blades with complex shape configurations, but also to provide substantial elements to successfully approach yaw-mechanics of tapered-swept rotor blades.

scholarly journals Modeling and simulation of forces applied to the horizontal axis wind turbine rotors by the vortex method coupled with the method of the blade element

2021 ◽  
Vol 12 (1) ◽  
pp. 413
Author(s):  
Ibtissem Barkat ◽  
Abdelouahab Benretem ◽  
Fawaz Massouh ◽  
Issam Meghlaoui ◽  
Ahlem Chebel
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Farms ◽  
Vortex Method ◽  
Operating Conditions ◽  
Horizontal Axis ◽  
Rotor Blades ◽  
Good Representation ◽  
Horizontal Axis Wind Turbine ◽  
Blade Element

This article aims to study the forces applied to the rotors of horizontal axis wind turbines. The aerodynamics of a turbine are controlled by the flow around the rotor, or estimate of air charges on the rotor blades under various operating conditions and their relation to the structural dynamics of the rotor are critical for design. One of the major challenges in wind turbine aerodynamics is to predict the forces on the blade as various methods, including blade element moment theory (BEM), the approach that is naturally adapted to the simulation of the aerodynamics of wind turbines and the dynamic and models (CFD) that describes with fidelity the flow around the rotor. In our article we proposed a modeling method and a simulation of the forces applied to the horizontal axis wind rotors turbines using the application of the blade elements method to model the rotor and the vortex method of free wake modeling in order to develop a rotor model, which can be used to study wind farms. This model is intended to speed up the calculation, guaranteeing a good representation of the aerodynamic loads exerted by the wind.

Description and Computer Modeling of a Ball-and-Socket Hub That Enables Teetering for Three-Bladed Wind Turbines

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Arnold Ramsland
Keyword(s):  
Wind Turbine ◽  
Computer Modeling ◽  
Horizontal Axis ◽  
Main Shaft ◽  
Horizontal Axis Wind Turbine ◽  
Out Of Plane ◽  
Cyclic Variations ◽  
Bending Loads ◽  
Rainflow Counting ◽  
The Impact

A horizontal axis wind turbine with a ball-and-socket hub is disclosed. The hub enables horizontal axis turbines with two or more blades to teeter in response to wind shear gradients. Computer modeling was done using existing and modified fast code in order to compare the new hub design with existing designs. Results show that a three-bladed turbine with the ball-and-socket hub provides very significant reductions in out-of-plane bending loads applied to the main shaft in comparison to a three-bladed turbine with a rigid hub. Results also show that the new hub design provides significant reductions in the out-of-plane loads applied to the blades. A blade fatigue study using a rainflow counting of multi-axial torque contributions at the blade root was performed in order to assess the impact of these reductions, and results show that the three-bladed turbine equipped with a ball-and-socket, teetering hub provides for very significant reductions in lifetime blade damage in comparison to existing wind turbine designs due to a combination of factors. The first factor is that teetering largely eliminates the cyclic variations in out-of-plane torque on the blades that are observed with rigid hubs. Here, the fatigue study shows that the three-bladed wind turbine with a teetering hub provides for an approximate sixfold reduction in lifetime blade damage in comparison to a three-bladed turbine with a rigid hub. The second factor is that the addition of a third blade reduces the load on each blade by one-third. Here, the fatigue study shows that a three-bladed turbine with a teetering hub provides for an approximate fourfold reduction in lifetime blade damage in comparison to a two-bladed turbine with a teetering hub.

Assessment of a FEM-Based Formulation for Horizontal Axis Wind Turbine Rotors Aeroelasticity

2015 ◽  
Vol 798 ◽  
pp. 75-84 ◽  
Author(s):  
Angelo Calabretta ◽  
Claudio Testa ◽  
Luca Greco ◽  
Massimo Gennaretti
Keyword(s):  
Finite Element ◽  
Wind Turbine ◽  
Degrees Of Freedom ◽  
Unsteady Aerodynamics ◽  
Horizontal Axis ◽  
Rotor Blades ◽  
Elastic Response ◽  
Elastic Behaviour ◽  
Beam Model ◽  
Horizontal Axis Wind Turbine

This paper presents an aeroelastic formulation based on the Finite Element Method (FEM) for performance and stability predictions of isolated horizontal axis wind turbines. Hamilton’s principle is applied to derive the equations of blade aeroelasticity, by coupling a nonlinear beam model with Beddoes-Leishman sectional unsteady aerodynamics. A devoted fifteen-degrees-of-freedom finite element to model kinematics and elastic behaviour of rotating blades is introduced. Spatial discretization of the aeroelastic equations is carried-out to derive a set of coupled nonlinear ordinary differential equations solved by a time-marching algorithm. The proposed formulation may be enhanced to face the analysis of advanced-shape blades, as well as the inclusion of the presence of the tower, and represents the first step of an ongoing activity on wind energy based on a FEM approach; as a consequence, results have to be considered as preliminary. Due to similarities between wind turbine and helicopter rotor blades aeroelasticity, validation results firstly concern with the aeroelastic response of helicopter rotors in hovering. Next, the performance of a wind turbine in terms of blade elastic response and delivered thrust and power is predicted and compared to that provided by a validated aeroelastic solver based on a modal approach as well as with experimental data.

scholarly journals Design and Simulation of Small-Scale Horizontal-Axis Wind Turbine with Diffuser Effect

2019 ◽  
Vol 252 ◽  
pp. 04005
Author(s):  
Zbigniew Czyż ◽  
Paweł Karpiński ◽  
Tomasz Klepka ◽  
Zbigniew Szkoda
Keyword(s):  
Wind Turbine ◽  
Geometric Model ◽  
Patent Application ◽  
Horizontal Axis ◽  
Rotor Blades ◽  
Small Scale ◽  
Horizontal Axis Wind Turbine ◽  
Ansys Fluent ◽  
Power Generating Unit ◽  
Rotor Assembly

The article presents the results of the investigation of a rotor assembly of a wind turbine with a horizontal axis of rotation. The rotor is equipped with a diffuser which is an integral part of the power generating unit. The research was carried out by means of the ANSYS Fluent software. The geometry used for the tests is a development version of the construction shown in patent application PL 412553 and is characterised by an adjustable angle setting of the rotor blades. The geometric model was obtained by 3D scanning of the actual rotor using the ZScaner scanner ®700. The calculations were carried out for the selected blade angle of attack from 0° to 90° separately for the version with and without the diffuser. The results from the conducted tests were used to determine the characteristics of the power generated by the turbine as a function of rotor speed. The secondary objective of the tests was to analyse the effect of the diffuser on the power generated by the entire rotor assembly.

scholarly journals Aerodynamic analysis of backward swept in HAWT rotor blades using CFD

2018 ◽  
Vol 7 (3) ◽  
pp. 241-249 ◽  
Author(s):  
Mohammad Sadegh Salari ◽  
Behzad Zarif Boushehri ◽  
Mehrdad Boroushaki
Keyword(s):  
Renewable Energy ◽  
Wind Turbine ◽  
Reference Frame ◽  
Output Power ◽  
Horizontal Axis ◽  
Rotor Blades ◽  
Horizontal Axis Wind Turbine ◽  
Axial Thrust ◽  
Aerodynamic Analysis ◽  
Wind Velocities

The aerodynamical design of backward swept for a horizontal axis wind turbine blade has been carried out to produce more power at higher wind velocities. The backward sweep is added by tilting the blade toward the air flow direction. Computational Fluid Dynamics (CFD) calculations were used for solving the conservation equations in one outer stationary reference frame and one inner rotating reference frame, where the blades and grids were fixed in reference to the rotating frame. The blade structure was validated using Reynolds Averaged Navier-Stokes (RANS) solver in a test case by the National Renewable Energy Laboratory (NREL) VI blades results. Simulation results show considerable agreement with the NREL measurements. Standard K-ε turbulence model was chosen for simulations and for the backward swept design process. A sample backward sweep design was applied to the blades of a Horizontal Axis Wind Turbine (HAWT) rotor, and it is obtained that although at the lower wind velocities the output power and the axial thrust of the rotor decrease, at the higher wind velocities the output power increases while the axial thrust decreases. The swept blades have shown about 30 percent increase in output power and about 12 percent decrease in thrust at the wind speed of 14 m/s.Article History: Received June 23rd 2018; Received in revised form Sept 16th 2018; Accepted October 1st 2018; Available onlineHow to Cite This Article: Salari, M.S., Boushehri, B.Z. and Boroushaki, M. (2018). Aerodynamic Analysis of Backward Swept in HAWT Rotor Blades Using CFD. International Journal of Renewable Energy Development, 7(3), 241-249.http://dx.doi.org/10.14710/ijred.7.3.241-249

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