Wind Tunnel Aerodynamic Tests of Six Airfoils for Use on Small Wind Turbines

Selig, Michael S.; McGranahan, Bryan D.

doi:10.2514/6.2004-1188

Cited by 179 publications

(56 citation statements)

References 9 publications

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“…The simulation results are compared with the University of Illinois at Urbana‐Champaign wind tunnel measurements by Selig and McGranahan. The chord Reynolds number for the present simulations was Re = 100, 000, which corresponds to a wind speed of 4.5 m s −1 . Unless indicated otherwise, all length scales and velocities were made dimensionless with the airfoil chord, c , and the approach flow velocity, u R .…”

Section: Blade Section Simulationsmentioning

confidence: 59%

“…For these conditions, laminar separation was observed in wind tunnel experiments at the University of Illinois at Urbana‐Champaign. As a reference and to allow for a comparison with the fixed airfoil wind tunnel experiments, a stationary non‐rotating blade section was considered first. Simulations were also carried out for blade sections at 20% and 80% blade radius.…”

Section: Discussionmentioning

confidence: 99%

“…On the narrower coarse grids, these structures are suppressed and more energy is contained in the 2D modes (spanwise structures). A comparison of the computed lift and drag coefficients with UIUC wind tunnel and XFoil data is provided in Figure . The computed lift coefficients are in closer agreement with the wind tunnel data for the coarse grids than for the fine grid.…”

Section: Blade Section Simulationsmentioning

confidence: 99%

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Numerical investigation of rotational augmentation for S822 wind turbine airfoil

et al. 2012

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Direct numerical simulations were carried out for an S822 wind turbine blade section at a chord Reynolds number of Re D 100;000 and an angle of attack of˛D 5°. Results for a stationary non-rotating blade section compare favorably with wind tunnel data by the University of Illinois at Urbana-Champaign and XFoil predictions. By adding volume forcing terms to the right-hand side of the Navier-Stokes equations, the Coriolis and centrifugal accelerations resulting from blade rotation are modeled in the blade section simulations. Blade rotation is shown to delay separation especially near the hub, resulting in a lift increase of up to 100% and a drag reduction. The simulations provide insight into a physical mechanism that offers an explanation for the lift increase observed for rotating blade sections when compared with stationary blade sections, which is commonly referred to as rotational augmentation. Rotation is shown to lead to a radial velocity component toward the blade tip in areas where the velocity is substantially different from its free-stream value, such as near the stagnation point and especially in the separated flow region, and to the appearance of stationary and traveling crossflow vortices. A linear stability theory analysis that compares favorably with the simulation data provides proof that the primary instabilities are of a mixed type, including both a two-dimensional mode (Tollmien-Schlichting and Kelvin-Helmholtz type) and a stationary and unsteady crossflow mode. The crossflow instabilities accelerate transition, leading to separation delay, lift increase and drag reduction. This effect is very pronounced at 20% blade radius and still present at 80% radius. Because periodicity conditions were applied in the spanwise direction, the present results provide an explanation for rotational augmentation that is not based on the transfer of fluid from the inboard region toward the blade tip ('centrifugal pumping'). For the low Reynolds number conditions considered here, crossflow instabilities, which destabilize the flow leading to earlier transition and a separation delay, may contribute to rotational augmentation.Accurate blade performance predictions are crucially needed during wind turbine development. A survey of numerical methods for analysing the aerodynamic and aeroelastic properties of wind turbines was provided by Hansen et al. 1 Blade element momentum theory (BEMT) is one of the main tools for computing the performance of entire turbines. This approach was found to perform well for attached flow conditions but underestimate the stall onset and hence the peak power output when two-dimensional (2D) airfoil data are used that are not corrected for rotational effects. For example, the National Renewable Energy Laboratory (NREL) Combined Experiment (Phase II) turbine power exceeded predictions by approximately 15-20%. 2 Almost all research suggests that this effect can be attributed to stall delay caused by blade rotation. 3The survey paper by Leishman et al. 4 points out that many details of the...

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Section: Blade Section Simulationsmentioning

confidence: 59%

Section: Discussionmentioning

confidence: 99%

Section: Blade Section Simulationsmentioning

confidence: 99%

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Numerical investigation of rotational augmentation for S822 wind turbine airfoil

et al. 2012

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“…As detailed in Ref. 25, the turbulence intensity of the wind tunnel was measured to be less than 0.1%.…”

Section: A Facilitymentioning

confidence: 92%

Propeller Induced Flow Effects on Wings at Low Reynolds Numbers

Krishnan

Deters

Selig

2013

31st AIAA Applied Aerodynamics Conference

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Significant performance benefits have been found for a wing with a propeller in the tractor configuration at low Reynolds numbers (30,000 to 80,000) based on the wing chord. Propeller induced flow experiments on a wing with an aspect ratio of 4 using the Wortmann FX 63-137 airfoil show that an increase in propeller rotation rate (decreasing advance ratio) results in lift-to-drag ratios as high as 10 to 12 (a maximum of 80% increase in lift-to-drag ratio from a clean wing configuration) at both low and high angles of attack up to stall (0 to 16 deg). Experiments performed using trips and upper surface oil flow visualization results show that the turbulated nature of the propeller slipstream induces early transition to turbulent flow over the central portion of the wing. The result is a reduction of pressure drag and an increase in lift of the wing. The effect is greatest at low angles of attack. Additionally, results are presented where the location of the propeller was varied with respect to the wing, including having the propeller in a pusher configuration. The results show that to maximize the performance of small-scaled unmanned aerial vehicles (UAV) it is critical to properly integrate the propeller in a way that minimizes adverse low Reynolds number flow effects on the aerodynamics of a small-scaled UAV. * Graduate Student (Ph.D.), 104 S. Wright St., AIAA Student Member. anandak1@illinois.edu † Graduate Student (Ph.D.), 104 S. Wright St., AIAA Student Member. rdeters@illinois.edu ‡ Associate Professor, 104 S. Wright St., AIAA Senior Member. m-selig@illinois.edu

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“…Airfoil self noise has been extensively studied using computational methods and wind tunnel experimental measurements in Bertagnolio et al , Lutz et al and Selig and McGranahan. In some cases, inflow turbulence noise has been measured by installing a grid in the wind tunnel to create turbulence; however, turbulence‐generated sound levels depend on the atmospheric turbulence levels in the incoming flow that may be much lower than turbulence intensities produced in the wind tunnel. Also, the atmospheric turbulence spectral distribution may be difficult to reproduce experimentally.…”

Section: Introductionmentioning

confidence: 99%

On the use of a linear microphone array to measure wind turbine aerodynamic noise

et al. 2012

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A linear microphone array is shown to be a simple tool to locate aerodynamic sound sources on a horizontal axis wind turbine. This paper discusses the capabilities and limitations of a linear microphone array to locate sound sources and measure aerodynamic noise on the blades of a horizontal axis wind turbine rotor. Compared with a planar microphone array, a linear array requires fewer microphones to achieve the same resolution, a simpler structure to support it and a simpler signal processing algorithm. For a linear array, areas exist in the rotor plane where the sources cannot be located unambiguously. For certain applications, it is not necessary to map the whole rotor plane. This paper also shows the result of an experimental test aimed at locating and measuring aerodynamic sound sources on the three blades of a wind turbine. Each blade received a different surface treatment, with the goal of comparing their relative sound emission levels. The test was carried out with a 10.32 m linear microphone array, placed horizontally near the ground, extending parallel to the rotor plane. The results show that for all three blades, most of the noise is generated in the outer 25% of the blade span, with a maximum occurring just after the blade has passed the horizontal position going downwards. Results also show that tripped blade is the noisiest of the three, whereas the smoothest, polished blade is clearly the quietest.

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Wind Tunnel Aerodynamic Tests of Six Airfoils for Use on Small Wind Turbines

Cited by 179 publications

References 9 publications

Numerical investigation of rotational augmentation for S822 wind turbine airfoil

Numerical investigation of rotational augmentation for S822 wind turbine airfoil

Propeller Induced Flow Effects on Wings at Low Reynolds Numbers

On the use of a linear microphone array to measure wind turbine aerodynamic noise

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