scholarly journals Research on the Influence of Shear Turbulence on the Aerodynamic Loads Characteristics of Wind Turbine

2021 ◽  
Vol 2087 (1) ◽  
pp. 012014
Author(s):  
Tong Tong ◽  
Bangxing Li ◽  
Xin Ren
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Turbulence Intensity ◽  
Phase Lag ◽  
Small Reduction ◽  
Numerical Accuracy ◽  
Aerodynamic Loads ◽  
Lag Effect ◽  
Shear Turbulence ◽  
Thrust And Torque

Abstract In order to accurately analysis the aerodynamic loads characteristics of the wind turbine under different turbulent wind conditions, the horizontal homogeneity in the flow field without a wind turbine and the numerical accuracy of the homogeneous flow field with a wind turbine were validated against the experimental results. The aerodynamic loads of the wind turbine were studied under the conditions of the uniform wind with a uniform turbulence intensity, the uniform wind with a shear turbulence intensity, the shear wind with a uniform turbulence intensity and the shear wind with a shear turbulence intensity. The results show that the increasing turbulence intensity leads to a small reduction in the torque of the wind turbine. Compared with uniform wind, shear inflow leads to a sine or cosine variation in the aerodynamic performance of the wind turbine and a reduction in the wind turbine’s thrust and torque. Compared with uniform turbulence intensity, shear turbulence intensity leads to a reduction in the wind turbine’s thrust and torque, and a more obvious phase lag effect, but it has little influence on the yawing moment and pitching moment.

CFD Sensitivity Analysis of a Straight-Blade Vertical Axis Wind Turbine

2012 ◽  
Vol 36 (5) ◽  
pp. 571-588 ◽  
Author(s):  
Khaled M Almohammadi ◽  
D B Ingham ◽  
L Ma ◽  
M Pourkashanian
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Wind Turbine ◽  
Turbulence Intensity ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Computational Domain ◽  
Vertical Axis Wind Turbine ◽  
Airfoil Surface ◽  
Straight Blade

This paper investigates the flow field features and the predicted power coefficient of a straight blade vertical axis wind turbine (SB-VAWT) using computational fluid dynamics modeling using 2D simulations. The Unsteady Navier-Stokes equations are solved with the concept of Reynolds averaging using the commercial software FLUENT and the sliding mesh technique is applied. In the mesh phase, three parameters have been investigated, namely the cell type, the cell aspect ratio on the airfoil surface, and the total number of cells in the computational domain. In the simulation phase, two parameters have been investigated, namely the time step/Courant number, and the turbulence intensity. Significant differences have been observed in the flow field features and on the predicted power coefficient for some of these parameters which if not considered in details could lead to unreliable predictions. The sensitivity of the parameters is not equally significant and this paper suggests which parameters should be focused on in the modeling process. The convergence behavior of the quadrilateral based mesh is found to be more consistent compared to the triangular based mesh. In the mesh phase, the cell aspect ratio on the airfoil surface was found to be a significant factor, whereas the turbulence intensity was found to be a significant fac-tor in the simulation phase.

Aero-Structural Analysis of Wind Turbine Blades With Sweep and Winglets: Coupling a Vortex Line Method to ADAMS/AeroDyn

2011 ◽  
Author(s):  
Mark E. Braaten ◽  
Arathi Gopinath
Keyword(s):  
Structural Analysis ◽  
Wind Turbine ◽  
Vortex Line ◽  
Turbine Blades ◽  
Suction Side ◽  
Wind Turbine Blades ◽  
Aerodynamic Loads ◽  
Straight Blade ◽  
Line Method ◽  
Thrust And Torque

The FAST/ADAMS/AeroDyn system of codes has been widely used to perform the aero-structural analysis of conventional wind turbine blades. Recent advances in blade design involve the development of aeroelastic tailored blades with large amounts of sweep, and blades with winglets. However, the existing Blade Element Momentum (BEM) approach in AeroDyn is limited to straight blades and does not account for sweep or dihedral effects. The goal of this work is to obtain higher fidelity aerodynamic loads predictions for such advanced blade designs. A Vortex Line Method (VLM) for computing aerodynamic loads has been coupled to ADAMS through modification of the existing AeroDyn interface. The VLM approach adopted here adds fidelity by modeling the effects of sweep, dihedral, 3D wakes, and wake dynamics. An existing steady/unsteady VLM code with these capabilities was restructured to allow its integration with AeroDyn. The FAST routines from NREL, which are used as a preprocessor to ADAMS, and the ADAMS/AeroDyn interface itself, were also modified to create an ADAMS model that properly accounts for the curvature of the blade that occurs when large amounts of sweep or winglets are present. The resulting ADAMS/VLM model was compared to the original ADAMS/BEM model for a straight blade and for a highly swept blade. The model was also applied to blades with pressure-side and suction-side winglet configurations. The BEM and VLM models give similar aero predictions for the straight blade, as expected. The induced twist and blade deformations are found to be more similar for the two methods than the aerodynamic loads. Computations were made for the blades with the winglets at different wind speeds and different pitch settings, and results were obtained for blade deflection, induced twist, and thrust and torque force distributions.

Multiple Vortex Body Vortex Numerical Simulation

2011 ◽  
Vol 328-330 ◽  
pp. 1755-1758
Author(s):  
Han Xiao Liu ◽  
Zhong Liu ◽  
Huai Liang Li ◽  
Xin Xin Feng ◽  
Zhen Zhong Xing
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Turbulence Intensity ◽  
Continuity Equation ◽  
Momentum Equation ◽  
Turbulent Intensity ◽  
Good Effect ◽  
Train Of Thought

In this paper, the continuity equation, momentum equation and the k-ε turbulence equation were introduced to simulate the flow field of the multiple vortex bodies in different spacing cases. Found that each vortex body had good effect in producing vortex, and the greater flow field spacing, the smaller the highest velocity; the turbulence intensity is increasing gradually from the former vortex body to the next one, and there may be a best spacing between the vortex bodies which makes the best turbulent intensity. All of these theories provide a train of thought for the turbulent coalescence mechanism.

Simulation of Flow Field on a Large Scale Wind Turbine

2008 ◽  
Author(s):  
I. Janajreh ◽  
C. Ghenai
Keyword(s):  
Flow Field ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Cross Sections ◽  
Large Scale ◽  
Wind Farms ◽  
Operating Characteristics ◽  
Cross Sectional ◽  
Capital Costs

Large scale wind turbines and wind farms continue to evolve mounting 94.1GW of the electrical grid capacity in 2007 and expected to reach 160.0GW in 2010 according to World Wind Energy Association. They commence to play a vital role in the quest for renewable and sustainable energy. They are impressive structures of human responsiveness to, and awareness of, the depleting fossil fuel resources. Early generation wind turbines (windmills) were used as kinetic energy transformers and today generate 1/5 of the Denmark’s electricity and planned to double the current German grid capacity by reaching 12.5% by year 2010. Wind energy is plentiful (72 TW is estimated to be commercially viable) and clean while their intensive capital costs and maintenance fees still bar their widespread deployment in the developing world. Additionally, there are technological challenges in the rotor operating characteristics, fatigue load, and noise in meeting reliability and safety standards. Newer inventions, e.g., downstream wind turbines and flapping rotor blades, are sought to absorb a larger portion of the cost attributable to unrestrained lower cost yaw mechanisms, reduction in the moving parts, and noise reduction thereby reducing maintenance. In this work, numerical analysis of the downstream wind turbine blade is conducted. In particular, the interaction between the tower and the rotor passage is investigated. Circular cross sectional tower and aerofoil shapes are considered in a staggered configuration and under cross-stream motion. The resulting blade static pressure and aerodynamic forces are investigated at different incident wind angles and wind speeds. Comparison of the flow field results against the conventional upstream wind turbine is also conducted. The wind flow is considered to be transient, incompressible, viscous Navier-Stokes and turbulent. The k-ε model is utilized as the turbulence closure. The passage of the rotor blade is governed by ALE and is represented numerically as a sliding mesh against the upstream fixed tower domain. Both the blade and tower cross sections are padded with a boundary layer mesh to accurately capture the viscous forces while several levels of refinement were implemented throughout the domain to assess and avoid the mesh dependence.

Fully Coupled Three-Dimensional Dynamic Response of a TLP Floating Wind Turbine in Waves and Wind

2012 ◽  
Author(s):  
G. K. V. Ramachandran ◽  
H. Bredmose ◽  
J. N. Sørensen ◽  
J. J. Jensen
Keyword(s):  
Wind Turbine ◽  
Dynamic Model ◽  
Three Dimensional ◽  
Geographic Location ◽  
Climatic Conditions ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Total System ◽  
Wave Loads ◽  
Aerodynamic Loads

A dynamic model for a tension-leg platform (TLP) floating offshore wind turbine is proposed. The model includes three-dimensional wind and wave loads and the associated structural response. The total system is formulated using 17 degrees of freedom (DOF), 6 for the platform motions and 11 for the wind turbine. Three-dimensional hydrodynamic loads have been formulated using a frequency- and direction-dependent spectrum. While wave loads are computed from the wave kinematics using Morison’s equation, aerodynamic loads are modelled by means of unsteady Blade-Element-Momentum (BEM) theory, including Glauert correction for high values of axial induction factor, dynamic stall, dynamic wake and dynamic yaw. The aerodynamic model takes into account the wind shear and turbulence effects. For a representative geographic location, platform responses are obtained for a set of wind and wave climatic conditions. The platform responses show an influence from the aerodynamic loads, most clearly through a quasi-steady mean surge and pitch response associated with the mean wind. Further, the aerodynamic loads show an influence from the platform motion through more fluctuating rotor loads, which is a consequence of the wave-induced rotor dynamics. In the absence of a controller scheme for the wind turbine, the rotor torque fluctuates considerably, which induces a growing roll response especially when the wind turbine is operated nearly at the rated wind speed. This can be eliminated either by appropriately adjusting the controller so as to regulate the torque or by optimizing the floater or tendon dimensions, thereby limiting the roll motion. Loads and coupled responses are predicted for a set of load cases with different wave headings. Based on the results, critical load cases are identified and discussed. As a next step (which is not presented here), the dynamic model for the substructure is therefore being coupled to an advanced aero-elastic code Flex5, Øye (1996), which has a higher number of DOFs and a controller module.

Development and Validation of a CFD Technique for the Aerodynamic Analysis of HAWT

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
S. Gómez-Iradi ◽  
R. Steijl ◽  
G. N. Barakos
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Turbine Blades ◽  
Wind Tunnel Test ◽  
Unsteady Aerodynamics ◽  
Tunnel Wall ◽  
Local Flow ◽  
Flow Angle ◽  
Thrust And Torque

This paper demonstrates the potential of a compressible Navier–Stokes CFD method for the analysis of horizontal axis wind turbines. The method was first validated against experimental data of the NREL/NASA-Ames Phase VI (Hand, et al., 2001, “Unsteady Aerodynamics Experiment Phase, VI: Wind Tunnel Test Configurations and Available Data Campaigns,” NREL, Technical Report No. TP-500-29955) wind-tunnel campaign at 7 m/s, 10 m/s, and 20 m/s freestreams for a nonyawed isolated rotor. Comparisons are shown for the surface pressure distributions at several stations along the blades as well as for the integrated thrust and torque values. In addition, a comparison between measurements and CFD results is shown for the local flow angle at several stations ahead of the wind turbine blades. For attached and moderately stalled flow conditions the thrust and torque predictions are fair, though improvements in the stalled flow regime are necessary to avoid overprediction of torque. Subsequently, the wind-tunnel wall effects on the blade aerodynamics, as well as the blade/tower interaction, were investigated. The selected case corresponded to 7 m/s up-wind wind turbine at 0 deg of yaw angle and a rotational speed of 72 rpm. The obtained results suggest that the present method can cope well with the flows encountered around wind turbines providing useful results for their aerodynamic performance and revealing flow details near and off the blades and tower.

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