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Journal ArticleDOI

Effect of Reynolds Number on Aerodynamics of Airfoil with Gurney Flap

TL;DR: In this paper, the effect of variation in Reynolds number on the aerodynamics of the NACA 0012 airfoil without and with a Gurney flap of height of 3% chord is presented.
Abstract: Steady state, two-dimensional computational investigations performed on NACA 0012 airfoil to analyze the effect of variation in Reynolds number on the aerodynamics of the airfoil without and with a Gurney flap of height of 3% chord are presented in this paper. RANS based one-equation Spalart-Allmaras model is used for the computations. Both lift and drag coefficients increase with Gurney flap compared to those without Gurney flap at all Reynolds numbers at all angles of attack. The zero lift angle of attack seems to become more negative as Reynolds number increases due to effective increase of the airfoil camber. However the stall angle of attack decreased by 2° for the airfoil with Gurney flap. Lift coefficient decreases rapidly and drag coefficient increases rapidly when Reynolds number is decreased below critical range. This occurs due to change in flow pattern near Gurney flap at low Reynolds numbers.

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Citations
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Journal ArticleDOI
15 Nov 2019-Energy
TL;DR: In this article, the effects of Gurney flaps on the aerodynamic performance of a horizontal axis wind turbine, which is part of the EU FP7 AVATAR project, were investigated.

29 citations

Journal ArticleDOI
01 Feb 2022-Energies
TL;DR: In this article , an unsteady flow analysis of a 3D wing with a morphing trailing edge flap (TEF) and a seamless side-edge transition between the morphed and static parts of a wing was presented.
Abstract: This paper presents an unsteady flow analysis of a 3D wing with a morphing trailing edge flap (TEF) and a seamless side-edge transition between the morphed and static parts of a wing by introducing an unsteady parametrization method. First, a 3D steady Reynolds-averaged Navier–Stokes (RANS) analysis of a statically morphed TEF with seamless transition is performed and the results are compared with both a baseline clean wing and a wing with a traditional hinged flap configuration at a Reynolds number of 0.7 × 106 for a range of angles of attack (AoA), from 4° to 15°. This study extends some previous published work by examining the inherent unsteady 3D effects due to the presence of the seamless transition. It is found that in the pre-stall regime, the statically morphed wing produces a maximum of a 22% higher lift and a near constant drag reduction of 25% compared with the hinged flap wing, resulting in up to 40% enhancement in the aerodynamic efficiency (i.e., lift/drag ratio). Second, unsteady flow analysis of the dynamically morphing TEF with seamless flap side-edge transition is performed to provide further insights into the dynamic lift and drag forces during the flap motions at three pre-defined morphing frequencies of 4 Hz, 6 Hz, and 8 Hz, respectively. Results have shown that an initially large overshoot in the drag coefficient is observed due to unsteady flow effects induced by the dynamically morphing wing; the overshoot is proportional to the morphing frequency which indicates the need to account for dynamic morphing effects in the design phase of a morphing wing.

6 citations

Journal ArticleDOI
TL;DR: In this article, the flow characteristics and the lift and drag behavior of a thick trailing-edged airfoil that was provided with fixed trailing edge flaps (Gurney flaps) of 1% to 5% height right at the back of the aircraft were studied both experimentally and numerically at different low Reynolds numbers (Re) and angles of attack for possible applications in wind turbines suitable for the wind speeds of 4-6 m/s.
Abstract: The flow characteristics and the lift and drag behavior of a thick trailing-edged airfoil that was provided with fixed trailing edge flaps (Gurney flaps) of 1% to 5% height right at the back of the airfoil were studied both experimentally and numerically at different low Reynolds numbers (Re) and angles of attack for possible applications in wind turbines suitable for the wind speeds of 4-6 m/s. The flap considerably improves the suction on the upper surface of the airfoil resulting in a higher lift coefficient. The drag coefficient also increased; however, the increase was less compared to the increase in the lift coefficient, resulting in a higher lift-to-drag ratio in the angles of attack of interest. The results show that trailing-edge flaps can improve the performance of blades designed for low wind speeds and can directly be applied to small wind turbines that are increasingly being used in remote places or in smaller countries.

4 citations

References
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Journal ArticleDOI
TL;DR: In this article, a review of the research on Gurney flaps and related high lift trailing edge devices is presented, and a semi-empirical formula linking flap height to free stream speed and aerofoil chord is proposed, showing that the optimal size of the device is always below the boundary-layer thickness at the trailing edge.
Abstract: This paper reviews the research on Gurney flaps and related high lift trailing edge devices. It investigates aerofoil performances at Reynolds numbers Re ≅ 105 and below, both with the clean configuration and various Gurney flap sizes. The device height is optimised, and a semi-empirical formula linking flap height to free stream speed and aerofoil chord is proposed. The analysis shows that the optimal size of the device is always below the boundary-layer thickness at the trailing edge. Discussion of results includes analysis of hysteresis loops occurring in the L/D performances. These are mostly due to large changes in drag and small changes in lift, which occur when the aerofoil is restored to the reference angle of attack.

25 citations

Journal ArticleDOI
TL;DR: In this paper, a low-speed wind-tunnel investigation has been undertaken to establish the effect of a Gurney flap used in conjunction with a jet flap at low Reynolds numbers.
Abstract: A low-speed wind-tunnel investigation has been undertaken to establish the effect of a Gurney flap used in conjunction with a jet flap at low Reynolds numbers. The characteristics of the combination were explored as a potential control effector for small unmanned aerial vehicles. Measurements included force balance, wake survey, and flow visualization. The results indicate that the jet flap maintains a theoretically determined dependence on the jet momentum coefficient, even at a low Reynolds number (160,000). A numerical lifting-line program was modified to allow estimate of the rolling moment that may be generated by ailerons composed of a Gumey/jet flap. The numerical data suggest that the jet flap is capable of generating significant rolling moments with realistic jet momentum coefficients.

25 citations


"Effect of Reynolds Number on Aerody..." refers background or methods in this paper

  • ...Based on the equation for optimum GF given by Traub and Agarwal [8], the optimum GF height varies from 2.7 to 4.2% of airfoil chord as Reynolds number decreases from 3.0 × 105 to 3.0 × 104....

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  • ...[6], Brown and Filippone [7], and Traub and Agarwal [8] have studied the performance of airfoils at low Reynolds numbers but a systematic investigation is still not available....

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  • ...Mueller and Batill [5], Selig et al. [6], Brown and Filippone [7], and Traub and Agarwal [8] have studied the performance of airfoils at low Reynolds numbers but a systematic investigation is still not available....

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  • ...Based on the equation for optimum GF given by Traub and Agarwal [8], the optimum GF height varies from 2....

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Proceedings ArticleDOI
25 Jun 2012
Abstract: This paper presents wind tunnel results of wings of low-to-moderate aspect ratio (2≤A≤5) at low Reynolds numbers (60,000 to 160,000). Tests were conducted in the low-turbulence wind tunnel in the Subsonic Aerodynamics Research Laboratory at the University of Illinois at Urbana-Champaign (UIUC). A 3-component force/moment balance was designed and fabricated. The balance design methodology and validation are described in detail. Low Reynolds number tests performed on a wing having an aspect ratio of 4 and using the Wortmann FX 63-137 airfoil showed the existence of a critical Reynolds number of 90,000 for which a jump in performance characteristics was observed. Pre-stall and post-stall hysteresis was captured at the critical Reynolds number. Flow visualization photographs for the wing at different angles of attacks are presented. Finally, aerodynamic performance measurements taken for ten flat-plate rectangular and tapered wings are also presented and discussed.

20 citations

Journal ArticleDOI
TL;DR: In this article, the authors used a Reynolds-averaged Navier-Stokes finite volume flow solver to simulate the flowfields around a two-dimensional linear turbine cascade model at a Reynolds number of 25,000.
Abstract: This study uses a Reynolds-averaged Navier–Stokes finite volume flow solver to simulate the flowfields around a two-dimensional linear turbine cascade model at a Reynolds number of 25,000. Three blade profiles have been simulated, including the aft-loaded Pack B, which has a nominal Zweifel loading coefficient Zw equal to 1.15, the midloaded L1M (Zw=1.33), and the front-loaded L2F (Zw=1.59). All three blade profiles are known to be susceptible to varying degrees of laminar flow separation along the suction surface. Turbulence models used, which to the authors’ knowledge have been applied for the first time here, are the Abe–Kondoh–Nagano linear low-Re k-e as well as the Kato–Launder modification. Time-accurate simulations, including fully laminar computations, are compared with experimental data and higher-order computations to judge the accuracy of the results, where it is shown that Reynolds-averaged Navier–Stokes simulations with appropriate turbulence modeling can produce both quantitatively and quali...

7 citations


"Effect of Reynolds Number on Aerody..." refers methods in this paper

  • ...This is demonstrated by Arko and McQuilling [16], who used advanced turbulence models of Abe et al. [17, 18] and Kato and Launder [19]....

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  • ...This is demonstrated by Arko and McQuilling [16], who used advanced turbulence models of Abe et al....

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