scholarly journals Wake Effect of a Horizontal Axis Wind Turbine on the Performance of a Downstream Turbine

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2395 ◽  
Author(s):  
Haojun Tang ◽  
Kit-Ming Lam ◽  
Kei-Man Shum ◽  
Yongle Li
Keyword(s):  
Wind Turbine ◽  
Tangential Velocity ◽  
Streamwise Velocity ◽  
Horizontal Axis ◽  
Wake Flow ◽  
Wake Effect ◽  
Horizontal Axis Wind Turbine ◽  
Small Pitch ◽  
Swept Area ◽  
Wake Characteristics

This paper presents wind tunnel tests on the wake characteristics of a three-blade horizontal axis wind turbine and the wake effect on the performance of a downstream turbine. For a single turbine model, the performance was determined and this was followed by measurement of the wind characteristics including velocities, turbulence intensities, and correlation in the wake flow field. Subsequently, taking two horizontal axis wind turbines in a tandem arrangement into account, their performance was tested and the aerodynamic mechanism was discussed. The results showed that the upstream turbine with blades set at a small pitch angle provided smaller disturbance to the flow, but as the blade turned faster, larger changes in the velocity and the turbulence intensity occurred in its wake due to the more frequent disturbance of the wind turbine. The correlation of wake velocities in the turbine swept area also obviously decreased from the free-stream situation. For the downstream turbine, the output power loss largely depended on the wake characteristics of the upstream turbine, which was closely related to lower wind velocities or higher turbulence intensities. The decrease in correlation of the streamwise velocity within the blade swept area is accompanied by the increased correlation of the tangential velocity, which may be beneficial to the downstream turbine’s performance.

scholarly journals Numerical Study of Nacelle Wind Speed Characteristics of a Horizontal Axis Wind Turbine under Time-Varying Flow

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3993 ◽  
Author(s):  
Xiaodong Wang ◽  
Yunong Liu ◽  
Luyao Wang ◽  
Lin Ding ◽  
Hui Hu
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Horizontal Axis ◽  
Wake Flow ◽  
Horizontal Axis Wind Turbine ◽  
Inlet Flow ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Speed Condition ◽  
Simulation Results

Nacelle wind speed transfer function (NTF) is usually used for power prediction and operational control of a horizontal axis wind turbine. Nacelle wind speed exhibits high instability as it is influenced by both incoming flow and near wake of a wind turbine rotor. Enhanced understanding of the nacelle wind speed characteristics is critical for improving the accuracy of NTF. This paper presents Reynolds-averaged Navier–Stokes (RANS) simulation results obtained for a multi-megawatt wind turbine under both stable and dynamic incoming flows. The dynamic inlet wind speed varies in the form of simplified sinusoidal and superposed sinusoidal functions. The simulation results are analyzed in time and frequency domains. For a stable inlet flow, the variation of nacelle wind speed is mainly influenced by the blade rotation. The influence of wake flow shows high frequency characteristics. The results with stable inlet flow show that the reduction of the nacelle wind speed with respect to the inlet wind speed is overestimated for low wind speed condition, and underestimated for high wind speed condition. Under time-varing inflow conditions, for the time scale and fluctuation amplitude subject to the International Electrotechnical Commission (IEC) standard, the nacelle wind speed is mainly influenced by the dynamic inflow. The variation of inflow can be recovered by choosing a suitable low pass filter. The work in this paper demonstrates the potential for building accurate NTF based on Computational Fluid Dynamics (CFD) simulations and signal analysis.

scholarly journals Influence of the Heights of Low-Level Jets on Power and Aerodynamic Loads of a Horizontal Axis Wind Turbine Rotor

Atmosphere ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 132 ◽  
Author(s):  
Xuyao Zhang ◽  
Congxin Yang ◽  
Shoutu Li
Keyword(s):  
Wind Speed ◽  
Power Spectrum ◽  
Wind Turbine ◽  
Horizontal Axis ◽  
Horizontal Axis Wind Turbine ◽  
Aerodynamic Loads ◽  
Low Level ◽  
Low Level Jets ◽  
Inflow Conditions ◽  
Swept Area

The influence of the heights of low-level jets (LLJs) on the rotor power and aerodynamic loads of a horizontal axis wind turbine were investigated using the fatigue, aerodynamics, structures, and turbulence code. The LLJ and shear inflow wind fields were generated using an existing wind speed spectral model. We found that the rotor power predicted by the average wind speed of the hub height is higher than the actual power in relatively weak and shallow LLJ inflow conditions, especially when the LLJ height is located inside the rotor-swept area. In terms of aerodynamic loads, when the LLJ height is located inside the rotor-swept area, the root mean square (RMS) rotor thrust coefficient and torque coefficient increase, while the RMS rotor unbalanced aerodynamic load coefficients, including lateral force, longitudinal force, tilt moment, and yaw moment, decreased. This means that the presence of both positive and negative wind shear in the rotor-swept area not only increases the rotor power but also reduces the unbalanced aerodynamic loads, which is beneficial to the operation of wind turbine. Power spectrum analysis shows no obvious difference in the power spectrum characteristics of the rotor torque and thrust in LLJ inflow conditions with different heights.

Effect of surge motion on rotor aerodynamics and wake characteristics of a floating horizontal-axis wind turbine

Energy ◽  
2021 ◽  
Vol 218 ◽  
pp. 119519
Author(s):  
Yuan Fang ◽  
Gen Li ◽  
Lei Duan ◽  
Zhaolong Han ◽  
Yongsheng Zhao
Keyword(s):  
Wind Turbine ◽  
Horizontal Axis ◽  
Horizontal Axis Wind Turbine ◽  
Rotor Aerodynamics ◽  
Wake Characteristics

PIV Experiment on Near Wake Flow of Horizontal Axis Wind Turbine

2013 ◽  
Vol 718-720 ◽  
pp. 1811-1815 ◽  
Author(s):  
Xiang Gao ◽  
Jun Hu ◽  
Zhi Qiang Wang
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Radial Direction ◽  
Three Dimensional ◽  
Horizontal Axis ◽  
Tip Vortex ◽  
Wake Flow ◽  
Horizontal Axis Wind Turbine ◽  
Near Wake ◽  
Piv Measurement

A three-dimensional horizontal axis wind turbine model was experimentally studied. The experiment was carried out in a laboratory wind tunnel. With PIV measurement, details about flow fields in the near wakeof the turbine blade were obtained. The result shows vortices generateon the tailing edge of the blade, and propagatedownstream then dissipate into small vortices. Vortices also generate at the tip of the blade, propagate downstream and along the radial direction then dissipate. The dissipation of the tip vortex is slower than the former. We also find that the wake of turbine blade rotates in the opposite direction of the blade.

scholarly journals Parametric study of flapwise and edgewise vibration of horizontal axis wind turbine blades

2021 ◽  
Vol 13 (9) ◽  
pp. 168781402110508
Author(s):  
Hamza Diken ◽  
Saeed Asiri
Keyword(s):  
Wind Turbine ◽  
Natural Frequency ◽  
Pitch Angle ◽  
Natural Frequencies ◽  
Slenderness Ratio ◽  
Ritz Method ◽  
Lagrange Function ◽  
Horizontal Axis ◽  
Horizontal Axis Wind Turbine ◽  
Small Pitch

In this paper, flapwise and edgewise vibrations of a horizontal axis wind turbine (HAWT) blade are studied. Rayleigh-Ritz method is used in which; orthogonal mode functions of the Euler-Bernoulli beam having fixed-free boundary are introduced into the Lagrange function and then the dynamic equations are derived. Effect of gravity, pitch angle, centrifugal stiffening, and rotary inertia are considered. Nondimensional equations are obtained by defining nondimensional parameters like; natural frequency, blade rotation, slenderness ratio, and simple pendulum frequency. The stiffness term of the natural frequency has two speed dependent elements and it is shown that, for small pitch angles, flapwise natural frequencies of the blade are increased by the increasing blade speed while the edgewise natural frequencies of the blade are decreased with the increasing blade speed. Pitch angle values ranging from 0° to 15° has negligible effect on the nondimensional natural frequencies of the blade up to the nondimensional blade speed of 4. Since the natural frequencies are the function of the blade speed, rotor critical speeds should be calculated with Campbell diagrams. Vibrational response of the blade tip to the gravity is dominant and much greater than that of the wind speed in the edgewise and flapwise vibration.

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