scholarly journals Measurement in a wind tunnel of the modification of mean wind and turbulence characteristics due to induction effects near wind turbine rotors

1987 ◽  
Author(s):  
D.E. Neff ◽  
R.N. Meroney
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Turbulence Characteristics ◽  
Turbine Rotors

Analyzing the Effect of Shaft and End-Plates of a Newly Developed Elliptical-Bladed Savonius Rotor From Wind Tunnel Tests

2019 ◽  
Author(s):  
Nur Alom ◽  
Nitish Kumar ◽  
Ujjwal K. Saha
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Maintenance Cost ◽  
Horizontal Axis Wind Turbine ◽  
Lower Efficiency ◽  
Wind Tunnel Tests ◽  
Savonius Rotor ◽  
Turbine Rotors

Abstract In recent times, drag-based vertical-axis wind turbine rotors have gained increasing interests in offshore applications because of their performance potential and reliability. Their advantages like simplicity, easier manufacture and lower maintenance cost have attracted the researcher’s attention toward improving their design further. However, this type of rotor is still suffering from lower efficiency than the lift-based Darrius and the horizontal-axis wind turbine rotors. A recently developed elliptical-bladed Savonius rotor has shown its potential to harvest wind energy more efficiently. However, the geometric parameters of this rotor such as aspect ratio, overlap ratio, number of blades, shaft and end plates, the aerodynamic parameters such as Reynolds number, lift and drag coefficients are needed to be optimized for further improvement of its performance. In the present investigation, the wind tunnel tests have been conducted to analyze the effect of shaft and end-plates of a newly developed elliptical-bladed vertical-axis Savonius wind turbine rotor. Experiments have been conducted over a range of tip speed ratios to find the torque and power coefficients of a two-bladed rotor system for two individual cases viz., the rotor with a shaft and the rotor with end-plates. In order to have a direct comparison, the experimental data are also obtained for the same rotor without the shaft and without the end-plates. The wind tunnel tests have demonstrated an improvement of power coefficient by 26.31% for the rotor with the end plates.

Performance Optimization of Wind Turbine Rotors With Active Flow Control

2011 ◽  
Author(s):  
G. Pechlivanoglou ◽  
C. N. Nayeri ◽  
C. O. Paschereit
Keyword(s):  
Steady State ◽  
Wind Tunnel ◽  
Flow Control ◽  
Wind Turbine ◽  
Performance Optimization ◽  
Active Flow Control ◽  
Performance Criteria ◽  
Extensive Literature ◽  
Turbine Rotors ◽  
Active Flow

This paper presents a series of investigations performed at the Hermann Fo¨ttinger Institute of TU Berlin. The initial scope of the investigations was the identification of Active Flow Control (AFC) solutions with significant implementation potential on wind turbine rotors. Several Active Flow Control solutions were thoroughly investigated based on extensive literature research. The performance of all the investigated solutions was ranked according to objective performance criteria and then the best performing solutions were selected for further numerical and experimental investigation. The selected Active Flow Control solutions were experimentally investigated with steady state wind tunnel measurements as well as steady state CFD simulations. The results of these investigations and the potential of each AFC solution are presented and discussed. The steady state tests were followed by a dynamic wind tunnel test campaign where the performance of one AFC solution (active Gurney flap) on a pitching test wing was investigated. The results of the static and dynamic investigations were very positive and proved the large load reduction potential of AFC on wind turbines.

Experimental investigations of flow over NACA airfoils 0021 and 4412 of wind turbine blades with and without Tubercles

2021 ◽  
pp. 0309524X2110071
Author(s):  
Usman Butt ◽  
Shafqat Hussain ◽  
Stephan Schacht ◽  
Uwe Ritschel
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Wind Turbine ◽  
Critical Region ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Experimental Investigations ◽  
Wind Turbine Blades

Experimental investigations of wind turbine blades having NACA airfoils 0021 and 4412 with and without tubercles on the leading edge have been performed in a wind tunnel. It was found that the lift coefficient of the airfoil 0021 with tubercles was higher at Re = 1.2×105 and 1.69×105 in post critical region (at higher angle of attach) than airfoils without tubercles but this difference relatively diminished at higher Reynolds numbers and beyond indicating that there is no effect on the lift coefficients of airfoils with tubercles at higher Reynolds numbers whereas drag coefficient remains unchanged. It is noted that at Re = 1.69×105, the lift coefficient of airfoil without tubercles drops from 0.96 to 0.42 as the angle of attack increases from 15° to 20° which is about 56% and the corresponding values of lift coefficient for airfoil with tubercles are 0.86 and 0.7 at respective angles with18% drop.

Production of Shear Profiles in a Wind Tunnel by Cylindrical Rods Placed Normal to the Stream

1966 ◽  
Vol 70 (667) ◽  
pp. 724-725 ◽  
Author(s):  
D. J. Cockrell ◽  
B. E. Lee
Keyword(s):  
Wind Tunnel ◽  
Velocity Profiles ◽  
Wind Effects ◽  
Turbulence Characteristics ◽  
Fluid Behaviour

The production of required velocity profiles in a duct or wind tunnel is a necessary part of much research aimed at understanding fluid behaviour. Perhaps the most obvious application is the simulation of wind gradients for the study of wind effects on structures, but equally important is the study of diffuser and duct behaviour when subjected to a variety of known and convenient velocity profiles. Furthermore, the effects of the variation in turbulence characteristics within a range of identical velocity profiles produced by different methods are not clearly understood.

Comparison of Wind Tunnel Airfoil Performance Data With Wind Turbine Blade Data

1992 ◽  
Vol 114 (2) ◽  
pp. 119-124 ◽  
Author(s):  
C. P. Butterfield ◽  
George Scott ◽  
Walt Musial
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Peak Power ◽  
Unsteady Aerodynamics ◽  
Leading Edge ◽  
Operating Conditions ◽  
Performance Data ◽  
Horizontal Axis Wind Turbine ◽  
Force Coefficients ◽  
Basic Fluid

Horizontal axis wind turbine (HAWT) performance is usually predicted by using wind tunnel airfoil performance data in a blade element momentum theory analysis. This analysis assumes that the rotating blade airfoils will perform as they do in the wind tunnel. However, when stall-regulated HAWT performance is measured in full-scale operation, it is common to find that peak power levels are significantly greater than those predicted. Pitch-controlled rotors experience predictable peak power levels because they do not rely on stall to regulate peak power. This has led to empirical corrections to the stall predictions. Viterna and Corrigan (1981) proposed the most popular version of this correction. But very little insight has been gained into the basic cause of this discrepancy. The National Renewable Energy Laboratory (NREL), funded by the DOE, has conducted the first phase of an experiment which is focused on understanding the basic fluid mechanics of HAWT aerodynamics. Results to date have shown that unsteady aerodynamics exist during all operating conditions and dynamic stall can exist for high yaw angle operation. Stall hysteresis occurs for even small yaw angles and delayed stall is a very persistent reality in all operating conditions. Delayed stall is indicated by a leading edge suction peak which remains attached through angles of attack (AOA) up to 30 degrees. Wind tunnel results show this peak separating from the leading edge at 18 deg AOA. The effect of this anomaly is to raise normal force coefficients and tangent force coefficients for high AOA. Increased tangent forces will directly affect HAWT performance in high wind speed operation. This report describes pressure distribution data resulting from both wind tunnel and HAWT tests. A method of bins is used to average the HAWT data which is compared to the wind tunnel data. The analysis technique and the test set-up for each test are described.

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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