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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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
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
11 Jan 2021
5 citations
01 Jan 2020
5 citations
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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Book•
01 Jan 1989
169 citations
"Effect of Reynolds Number on Aerody..." refers background in this paper
...[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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01 Apr 2000
TL;DR: In this article, a new platform force and moment balance, similar to an already existing balance, was designed and built to perform lift, drag and moment measurements at low Reynolds numbers Balance characteristics and validation data are presented Results show a good agreement between published data and data obtained with the new balance.
Abstract: : A description of the micro-air vehicle (MAV) concept and design requirements is presented These vehicles are very small and therefore operate at chord Reynolds numbers below 200,000 where very little data is available on the performance of lifting surfaces, ie, airfoils and low aspect-ratio wings This paper presents the results of a continuing study of the methods that can be used to obtain reliable force and moment data on thin wings in wind and water tunnels To this end, a new platform force and moment balance, similar to an already existing balance, was designed and built to perform lift, drag and moment measurements at low Reynolds numbers Balance characteristics and validation data are presented Results show a good agreement between published data and data obtained with the new balance Results for lilt, drag and pitching moment about the quarter chord with the existing aerodynamic balance on a series of thin flat plates and cambered plates at low Reynolds numbers are presented They show that the cambered plates offer better aerodynamic characteristics and performance Moreover, it appears that the trailing-edge geometry of the wings and the turbulence intensity up to about 1% in the wind tunnel do not have a strong effect on the lilt and drag for thin wings at low Reynolds numbers However, the presence of two endplates for two-dimensional tests and one endplate for the semi-infinite tests appears to have an undesirable influence on the lift characteristics at low Reynolds numbers
160 citations
22 Mar 1982
118 citations
"Effect of Reynolds Number on Aerody..." refers background in this paper
...Reynolds numbers between Re = 3 × 10(4) and 7× 10(4) are of great interest toMAVdesigners [9]....
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TL;DR: In this paper, surface pressure distributions and wake profiles were obtained for a NACA0012 airfoil to determine the lift, drag, and pitching-moment coefficients for various configurations.
Abstract: Experimental measurements of surface pressure distributions and wake profiles were obtained for a NACA0012 airfoil to determine the lift, drag, and pitching-moment coefficients for various configurations. The addition of a Gurney flap increased the maximum lift coefficient from 1.37 to 1.74, however there was a drag increment at low-to-moderate lift coefficient. In addition, the boundary layer profile measurements were taken using a rake of total pressure probes at the 90% chord location on the suction side. The effective Gurney flap height is about 2% of chord length, which provides the highest lift-to-drag ratio among the investigated configurations when compared with the clean NACA0012 airfoil. In this case, the device remains within the boundary layer.
112 citations
TL;DR: From the computational investigation, it is recommended that Gurney flaps with a height of 1.5% chord be installed perpendicular to chord and as close to the trailing edge as possible to obtain maximum lift enhancement with minimum drag penalty.
Abstract: The present study comprises steady state, two-dimensional computational investigations performed on NACA 0012 airfoil to analyze the effect of Gurney flap (GF) on airfoil aerodynamics using k-e RNG turbulence model of FLUENT. Airfoil with GF is analyzed for six different heights from 0.5% to 4% of the chord length, seven positions from 0% to 20% of the chord length from the trailing edge, and seven mounting angles from 30° to 120° with the chord. Computed values of lift and drag coefficients with angle of attack are compared with experimental values and good agreement is found at low angles of attack. In addition static pressure distribution on the airfoil surface and pathlines and turbulence intensities near the trailing edge are present. From the computational investigation, it is recommended that Gurney flaps with a height of 1.5% chord be installed perpendicular to chord and as close to the trailing edge as possible to obtain maximum lift enhancement with minimum drag penalty.
29 citations
"Effect of Reynolds Number on Aerody..." refers background in this paper
...Previous studies show that out of two equation RANS based models of FLUENT, κ-ε RNG model is best suited for the present airfoil study [12, 13]....
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