Characterization of Low Reynolds Number Wind Turbine Aerodynamics by BEM Theory and PIV Measurements

2010 ◽  
Author(s):  
A. Villegas Vaquero ◽  
Y. Cheng ◽  
V. del Campo ◽  
F. J. Di´ez
Keyword(s):  
Reynolds Number ◽  
Velocity Field ◽  
Wind Turbine ◽  
Low Reynolds Number ◽  
Water Channel ◽  
Horizontal Axis Wind Turbine ◽  
Thrust Coefficient ◽  
Wind Turbine Aerodynamics ◽  
Image Velocimetry ◽  
Low Reynolds

In this study, low Reynolds number wind turbine aerodynamics was considered. The overall goal was to characterize the flow in order to optimize the power output of the system. First, BEMT theory (Blade Element Momentum Theory) was formulated for this flow where Prandtl’s tip- and hub-loss corrections were included, as well as Glauert’s thrust coefficient correction. The theory was validated with experimental data from National Renewable Energy Laboratory (NREL) for larger scale wind turbines. Also, a physical model of a low Reynolds number horizontal-axis wind turbine (HAWT) was built. Particle Image Velocimetry (PIV) was used to calculate the velocity field around the HAWT. This allowed for planar measurements of the velocity field at different location in the wake of the rotor. The measurements were performed in a water channel allowing for better control of PIV seeding and improved flow visualization. PIV results allowed observation of the velocity field and vorticity field in the wake of the rotor. This data is currently being compared to BEMT theory suggesting good agreement.

scholarly journals New airfoils for micro horizontal-axis wind turbines

2021 ◽  
Author(s):  
Manoj Kumar Chaudhary ◽  
◽  
S. Prakash ◽  
Keyword(s):  
Reynolds Number ◽  
Wind Turbines ◽  
Low Reynolds Number ◽  
Horizontal Axis ◽  
Speed Ratio ◽  
Maximum Output ◽  
Horizontal Axis Wind Turbine ◽  
Horizontal Axis Wind Turbines ◽  
Low Reynolds ◽  
Bem Theory

In this study, small horizontal-axis wind turbine blades operating at low wind speeds were optimized. An optimized blade design method based on blade element momentum (BEM) theory was used. The rotor radius of 0.2 m, 0.4 m and 0.6 m and blade geometry with single (W1 & W2) and multistage rotor (W3) was examined. MATLAB and XFoil programs were used to implement to BEM theory and devise a six novel airfoil (NAF-Series) suitable for application of small horizontal axis wind turbines at low Reynolds number. The experimental blades were developed using the 3D printing additive manufacturing technique. The new airfoils such as NAF3929, NAF4420, NAF4423, NAF4923, NAF4924, and NAF5024 were investigated using XFoil software at Reynolds numbers of 100,000. The investigation range included tip speed ratios from 3 to 10 and angle of attacks from 2° to 20°. These parameters were varied in MATLAB and XFoil software for optimization and investigation of the power coefficient, lift coefficient, drag coefficient and lift-to-drag ratio. The cut-in wind velocity of the single and multistage rotors was approximately 2.5 & 3 m/s respectively. The optimized tip speed ratio, axial displacement and angle of attack were 5.5, 0.08m & 6° respectively. The proposed NAF-Series airfoil blades exhibited higher aerodynamic performances and maximum output power than those with the base SG6043 and NACA4415 airfoil at low Reynolds number.

Vortex Shedding Analysis in the Wake of a Flat Plate at Low Incidence and Low Reynolds Number

2021 ◽  
Author(s):  
Bastav Borah ◽  
Anand Verma ◽  
Vinayak Kulkarni ◽  
Ujjwal K. Saha
Keyword(s):  
Reynolds Number ◽  
Velocity Field ◽  
Flat Plate ◽  
Vortex Shedding ◽  
Low Reynolds Number ◽  
General Tendency ◽  
Flat Plates ◽  
Trailing Edge ◽  
Low Reynolds ◽  
Low Incidence

Abstract Vortex shedding phenomenon leads to a number of different features such as flow induced vibrations, fluid mixing, heat transfer and noise generation. With respect to aerodynamic application, the intensity of vortex shedding and the size of vortices play an essential role in the generation of lift and drag forces on an airfoil. The flat plates are known to have a better lift-to-drag ratio than conventional airfoils at low Reynolds number (Re). A better understanding of the shedding behavior will help aerodynamicists to implement flat plates at low Re specific applications such as fixed-wing micro air vehicle (MAV). In the present study, the shedding of vortices in the wake of a flat plate at low incidence has been studied experimentally in a low-speed subsonic wind tunnel at a Re of 5 × 104. The velocity field in the wake of the plate is measured using a hot wire anemometer. These measurements are taken at specific points in the wake across the flow direction and above the suction side of the flat plate. The velocity field is found to oscillate with one dominant frequency of fluctuation. The Strouhal number (St), calculated from this frequency, is computed for different angles of attack (AoA). The shedding frequency of vortices from the trailing edge of the flat plate has a general tendency to increase with AoA. In this paper, the generation and subsequent shedding of leading edge and trailing edge vortices in the wake of a flat plate are discussed.

scholarly journals Microscopic velocity field measurements inside a regular porous medium adjacent to a low Reynolds number channel flow

2019 ◽  
Vol 31 (4) ◽  
pp. 042001 ◽  
Author(s):  
A. Terzis ◽  
I. Zarikos ◽  
K. Weishaupt ◽  
G. Yang ◽  
X. Chu ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Porous Medium ◽  
Velocity Field ◽  
Channel Flow ◽  
Low Reynolds Number ◽  
Field Measurements ◽  
Low Reynolds
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