Effect Of Gurney Flap Research Articles

The effects of Gurney flap on the aerodynamic characteristics of two airfoils in non-continuum regimes

Gurney flap is a simple and effective high-lift device that has the potential to reduce the takeoff-and-landing distance for transport aircraft. It is also a good option for enhancing the airfoil cruising characteristics. However, its effectiveness in non-continuum regimes has rarely been studied. The Unified Gas Kinetic Scheme algorithm, which is valid for all flow regimes, is further developed and used to simulate the flow field around a cambered airfoil and a high-speed quadrilateral airfoil with and without the Gurney flap in the supersonic non-continuum flow regimes. The distribution function shapes at different spatial locations are provided and analyzed. The effects of angle of attack, free-stream Knudsen number, free-stream Mach number, Gurney flap height, and Gurney flap mounting angle on the aerodynamic characteristics of the two airfoils are studied. The results show that the lift and drag of the airfoil with the attached Gurney flap are increased. The pressure rise on the lower surface of the airfoil is the primary factor contributing to the increase in lift. The overall increase in drag mainly comes from the Gurney flap, which also generates a small amount of negative lift. When the angle of attack is less than the critical angle of attack, the Gurney flap can increase the lift-to-drag ratio of the airfoil and improve its aerodynamic performance. The critical angle of attack decreases with the increase in the free-stream Knudsen number and the free-stream Mach number. It decreases with increasing Gurney flap height and increases with increasing Gurney flap mounting angle.

Effects of Gurney Flaps on the Performance of a Horizontal Axis Ocean Current Turbine

Gurney flaps can enhance the hydrodynamic efficiency of airfoils, and they are currently used in several applications, including racing cars and wind turbines. However, there is a lack of studies in the literature on the application of Gurney flaps on the Horizontal Axis Ocean Current Turbine (HAOCT). The influence of Gurney flaps on the hydrodynamic efficiency of the HAOCT is evaluated through numerical analysis. The effect of the Gurney flaps on the turbine is evaluated after the validation of the utilized numerical method is completed using the wind tunnel experimental data of the two-dimensional NACA 63415 airfoil and the water tunnel experimental data of the NACA 638xx series rotor on the clean blade. By calculating the velocity and pressure fields of the 2D airfoil by CFD, it was possible to analyze the lift improvement with the addition of the Gurney flaps by evaluating the pressure difference between the pressure surface and the negative pressure surface, and the drag improvement was due to the Gurney flaps obstructing the chordal flow of the fluid in the wake. For the 2D NACA-63415 airfoil, the drag coefficient increases with the increase in the head angle, while the lift coefficient increases and then decreases. The flap height divided by the local chord length of the Gurney flaps is 0.01, and the lift-to-drag ratio is the highest when the head angle is 4°. For the NACA-638xx turbine, the addition of Gurney flaps significantly increases the axial thrust coefficient. At lower tip speed ratios, the effect of the Gurney flaps on the rotor’s power coefficient is limited, with the greatest increase in the power coefficient at a tip speed ratio of 6 and a decrease in the power coefficient increase as the tip speed ratio increases. Increasing the height of the Gurney flaps can increase the peak power coefficient, but the power performance decreases at high tip speed ratios. The Gurney flaps distributed at the root of the rotor have less effect on the power performance. A 0.4 local radius spread of the Gurney flaps increases the peak turbine power coefficient by only 0.34%, while full-length Gurney flaps can increase the peaked blade power coefficient by 10.68%, indicating that Gurney flaps can be used to design a new HAOCT.

Effect of gurney flaps on a nonslender delta wing during large-amplitude and high-frequency dynamic pitching

The flow control effect of Gurney flaps on 50° swept delta wings during large-amplitude and high-frequency pitching were investigated both experimentally and numerically. Both force and velocity measurements were conducted and compared with the numerical simulation results. The lift hysteresis was found to be significantly affected by the Gurney flaps. It was found that the leading-edge Gurney flap (LG) acts to redistribute the vorticity over the suction surface of the wing during the upstroke process. The formation and development of the leading-edge vortex (LEV) on the suction surface was delayed by the LG, which was accompanied by enhancement of the lift at high angles of attack. The lower surface pressure can be altered with the flow velocity being slowed down by the trailing-edge Gurney flap (TG), which improves overall lift performance of the pitching wing at small to moderate angles of attack.

Effect of Gurney Flap on the Aerodynamic Performance of a Flapping Foil: Micro-Aerial Vehicle Application

Abstract Even with its small size, the Gurney flap (GF) can help considerably in increasing the lift of foils and wings. To exploit this feature, the objective of this research was to numerically study the effects of this flow control device on the aerodynamic performance of oscillating foils for micro-aerial vehicle (MAV) applications. Three sets of each important parameter were selected: the height (0.01c, 0.04c, and 0.16c), angle (45 deg, 90 deg, and 135 deg) and location from trailing edge (T.E, 0.05c and 0.1c). A two-dimensional laminar, incompressible Navier–Stokes equation solver was used to computationally investigate the effect of the Gurney flap on the aerodynamic performance of a flat plate (chord length = 10 mm and thickness = 0.03c). It was found that the best aerodynamic performance was obtained when the Gurney flap was installed at the trailing edge with a height of 0.04c and mount angle of 90 deg. The height of the Gurney flap had a major impact on aerodynamic performance. Results showed an increase of 23.5% in mean lift coefficient, 15.5% in maximum lift coefficient, and 5% in power economy as compared to flat plate, which is accredited to the increase in effective camber and the formation of counter-rotating vortices, decreasing the adverse pressure gradient. The weakening of counter-rotating vortices downstream of Gurney flap could also be the contributing factor to its good performance. The results suggest that the Gurney flap may be useful in enhancing the performance of wings for bio-inspired flapping wing MAVs.

Effect of Gurney flap on the vortex-dominated flow over low-AR wings

Effect of Gurney flap on the vortex-dominated flow over low-AR wings

Study the effect of gurney flap on a wing's performance (AIRFOIL)

The paper discusses an aerodynamic modification (Gurney Flap) that is applied to an automobile's rear wing to boost the rear wings down force. The mod itself is low-cost and simple to implement. This technique increases the negative lift or lift by altering the pressure on the wing's top and lower surfaces. The flap does not need to be built of any unique material; it can be made of aluminium, wood, fibre, or any other light material and riveted or attached to the wing's trailing edge. It has been discovered from earlier study and computational fluid dynamics data that the gurney flap plays a key role in improving wing aerodynamics performance and how improved it is compared to the other wing with no gurney flap and conclusion has been made that what should be the geometry profile of Gurney flap.

The Effect of Gurney Flap and Trailing-edge Wedge on the Aerodynamic Behavior of an Axial Turbine Blade

In this research, the effect of Gurney flap and trailing-edge wedge on the aerodynamic behavior of blunt trailing-edge airfoil Du97-W-300 which is equipped with vortex generator is studied. To do this, the role of Gurney flap and trailing-edge wedge on the lift and drag coefficient and also aerodynamic performance of the airfoil is studied. Validation of the numerical model is performed by comparison of the obtained results with those of experiment. Results show that before stall, Gurney flap leads to the increase in the aerodynamic performance in a wider range of angle of attack. Numerical findings reveal that the maximum increment for the aerodynamic performance is obtained at low angle of attack when trailing-edge wedge is employed. It is found that for the highest considered value of Gurney flap and trailing-edge wedge heights, where the highest values for the lift occur, the higher aerodynamic performance at low angle of attack is obtained when trailing-edge wedge is used and at high angle of attack, the Gurney flap results in a higher aerodynamic performance. It is also shown that when high aerodynamic performance is concerned, addition of Gurney flap to the airfoil leads to the higher value for the lift. Doi: 10.28991/HIJ-2021-02-04-03 Full Text: PDF

Aerodynamic Characteristics of Airfoil and Vertical Axis Wind Turbine Employed with Gurney Flaps

In the present studies, the effects of Gurney flaps on aerodynamic characteristics of a static airfoil and a rotating vertical axis wind turbine are investigated by means of numerical approaches. First, mesh and time step studies are conducted and the results are validated with experimental data in good agreement. The numerical solutions demonstrate that the usage of Gurney flap increases the airfoil lift coefficient CL with a slight increase in drag coefficient CD. Furthermore, mounting a Gurney flap at the trailing edge of the blade increases the power production of the turbine considerably. Increasing the Gurney flap height further increases the power production. The best performance found is obtained for the maximum height used in this study at 6% relative to the chord. This is in contrast to the static airfoil case, which shows no further improvement for a flap height greater than 0.5%c. Increasing the angle of the flap decreases the power production of the turbine slightly but the load fluctuations could be reduced for the small value of the flap height. The present paper demonstrates that the Gurney flap height for high solidity turbines is allowed to be larger than the classical limit of around 2% for lower solidity turbines.

Numerical Investigation of Aerodynamic Characteristics of NACA 4312 Airfoil with Gurney Flap

This paper presents a two-dimensional Computational Fluid Dynamics (CFD) analysis on the effect of gurney flap on a NACA 4312 airfoil in a subsonic flow. These numerical simulations were conducted for flap heights 1.5%, 1.75%, 2% and 3% of chord length at fixed Reynold Number, Re (5×105) for different angle of attack (0o ~16o). ANSYS Fluent commercial software was used to conduct these simulations. The flow was considered as incompressible and K-omega Shear Stress Transport (SST) model was selected. The numerical results demonstrate that lift coefficient increase up to around 12o AoA (angle of attack) for NACA 4312 with and without gurney flap. For every AoA lift coefficient and drag coefficient presented proportionate behavior with flap height. However, lift co-efficient was decreased after around angle of attack due to flow separation. Maximum lift to drag ratio was found at around 4o AoA for every flap length and airfoil with flap of 1.5%C (chord length) had shown the most optimized aerodynamic performance through the analysis. This study concluded that airfoil with gurney flap displayed enhanced aerodynamic performance than the airfoil without gurney flap due to the delay in flow separation.

Research on the effect of a movable gurney flap on energy extraction of oscillating hydrofoil

A movable Gurney flap was used to enhance the energy extraction of the oscillating hydrofoil. According to the motion of oscillating hydrofoil, the position of Gurney flap was adjusted so that it was always on the pressure side of hydrofoil. The effect of Gurney flap with different length cg and different motion period R was studied under the condition of fixed Reynolds number with variations of kinematic parameters such as reduced frequency f ∗ and pitch amplitude θ. Numerical results show that the application of Gurney flaps significantly improves the average power and efficiency compared with no flap NACA0018 airfoil. By changing the flow structure and pressure distribution around the trailing edge of the airfoil, the Gurney flap facilitates the generation of lifting force, resulting in a higher power coefficient. The average power coefficienC¯P increases with the Gurney flap height cg between 1%c and 7%c, and further increases cg will not further increase energy extraction. When the Gurney flap movement period R is in the range of 2–6, the power coefficient increases as the value of R increases, however C¯P tends to be constant after R > 6. In addition, the increased cg results stronger trailing edge vortices and higher drag.

Aerodynamic effects of Gurney flaps on the rotor blades of a research wind turbine

Abstract. This paper investigates the aerodynamic impact of Gurney flaps on a research wind turbine of the Hermann-Föttinger Institute at the Technische Universität Berlin. The rotor radius is 1.5 m, and the blade configurations consist of the clean and the tripped baseline cases, emulating the effects of forced leading-edge transition. The wind tunnel experiments include three operation points based on tip speed ratios of 3.0, 4.3, and 5.6, reaching Reynolds numbers of approximately 2.5×105. The measurements are taken by means of three different methods: ultrasonic anemometry in the wake, surface pressure taps in the midspan blade region, and strain gauges at the blade root. The retrofit applications consist of two Gurney flap heights of 0.5 % and 1.0 % in relation to the chord length, which are implemented perpendicular to the pressure side at the trailing edge. As a result, the Gurney flap configurations lead to performance improvements in terms of the axial wake velocities, the angles of attack and the lift coefficients. The enhancement of the root bending moments implies an increase in both the rotor torque and the thrust. Furthermore, the aerodynamic impact appears to be more pronounced in the tripped case compared to the clean case. Gurney flaps are considered a passive flow-control device worth investigating for the use on horizontal-axis wind turbines.

Effect of Gurney flap on the aerodynamic behavior of an airfoil in mutational ground effect

In this research, the effect of Gurney flap on the aerodynamic behavior of an airfoil in mutational ground effect is investigated. To perform this, lift and drag coefficients of NACA 4412 airfoil section in the presence and absence of Gurney flap in mutational ground effect are evaluated and compared. To provide a better illustration of the effect of Gurney flap on the aerodynamic behavior of the airfoil section in the mutational ground effect, results are obtained during the takeoff and landing processes. Validation of the used numerical model is also performed by comparison of the obtained results with those of other works and reasonable agreements were seen. Results show that inclusion of Gurney flap to the airfoil leads to higher variations of lift and drag coefficients during takeoff and landing process. During the takeoff process, the flapped airfoil results in a higher lift decrement and drag increment although an increase in distance of airfoil from the ground or angle of attack causes the lift decrement of the flapped airfoil to get close to that of clean airfoil. It is shown that during takeoff process, downwash is generated around the airfoil as the airfoil leaves the step and as the airfoil gets away from the step, the generated downwash decreases. During the landing process, at each distance of airfoil form the ground and angle of attack, the lift decrement and drag increment of the flapped airfoil are significant compared to that of the clean airfoil. Results exhibit that during landing process, upwash is generated around the airfoil as the airfoil reaches the step and further airfoil move on the step leads to the decrease in the upwash. The decrement in lift coefficient and also the increment in drag coefficient during landing process are more remarkable than those in takeoff process.

The effect of gurney flap on flow characteristics of vertical axis wind turbine

Recently, the Gurney Flap (GF) has been used to improve the performance of Horizontal Axis Wind Turbine (HAWT) by enhancing its lift coefficient. Compared to HAWT, research on GF application for Vertical Axis Wind Turbine (VAWT) is very limited. Moreover, most works studied a GF geometry attached to the trailing edge of a stationary airfoil, without considering the rotating effect experienced by VAWT. For this reason, a three-straight-bladed VAWT rotating blade with GF is studied by transient RANS simulation together with a stress-blended eddy simulation (SBES) turbulence model to investigate the GF height effect and the flow characteristics near the blade trailing edge. Results have shown that by introducing the blade rotating, an optimum GF height is found to be 3% of the blade chord, slightly higher than 2% chord in a stationary airfoil case. In addition, the presence of GF can delay deep stall of VAWT blades, thus eliminating negative instantaneous moment coefficient and improving the turbine performance.

Effect of Gurney Flap on Performance and Aeroacoustics of Variable-Pitch Axial Fans

For a variable-pitch axial fan with guide vanes, the effect of three series of Gurney flaps (GFs) configured at the trailing edge of blades on the performance and dynamics is numerically investigated; and the aerodynamic noise is predicted. Simulated results show that GFs increase the total pressure rise of the fan; the higher the GF height, the more notable the lifting capacity. The working point of the highest efficiency moves toward the large flow rate. GF0.5-100 extends the high-efficiency scope and increases efficiency by an average of 2.09%; and GF2-50R raises efficiency by an average of 1.12%. After implementing a GF, the dynamics in the impeller distinctly. Compared with the original fan, a secondary tip leakage vortex generated at the blade tip aggravates the leakage loss; a pair of shedding vortices generated in the downstream of the trailing edge promotes the pressure difference between the suction and pressure surfaces. The prediction with the large-eddy simulation method indicates that GFs heighten the aerodynamic noise of the fan, and GF0.5-100 and GF2-50R increase the sound pressure level by 12 and 13 dB, respectively. Although the GF0.5-100 and GF2-50R are preferred choices for such axial fans, some necessary measures should be taken to reduce the acoustic noise in practical applications.

Effect of Gurney flap on flow separation and aerodynamic performance of an airfoil under rain and icing conditions

In the present study, special attention is paid to numerically investigate the aerodynamic performance of the NACA 0012 airfoil under rain and icing conditions with the aim to better understand the severe aerodynamic performance penalties of aircraft in flight. Furthermore, in order to control the flow separation and improve the aerodynamic performance of the airfoil under critical atmospheric conditions, the Gurney flap with different heights is attached to the trailing edge of the airfoil. The simulation is done at a Reynolds number of 3.1 × 105 under different atmospheric conditions including dry, rain, icing and coupling of rain and icing conditions. A two-way momentum coupled Eulerian–Lagrangian multiphase method is used to simulate the process of water film layer formed on the airfoil surface due to rainfall. According to the results, accumulation of water due to rainfall and ice accretion on the airfoil surface inevitably provides notable negative effects on the aerodynamic performance of the airfoil. It is concluded that icing induces a higher aerodynamic degradation than rain due to very intensive ice accretion. The Gurney flap as a passive flow control method with a favorable height for each condition is very beneficial. The maximum increment of the lift-to-drag ratio is achieved by Gurney flap with a height of 0.01 of airfoil chord length for dry and rain conditions and 0.02 of airfoil chord length for icing and coupling of rain and icing conditions, respectively.

Study of Eppler 423 Airfoil with Gurney Flap and Vortex Generators

In the past extensive research has been carried out, to study the effect of Gurney flap (GF) on symmetric and cambered airfoil for its usage in low Reynolds number regime. Use of GF at the trailing edge of the airfoil enhances the lift due to increase in the effective camber of the airfoil, which in turn improves the aerodynamic efficiency i.e. Cl/Cd. In the present study, Eppler 423 airfoil is used to first understand the aerodynamics of such a highly cambered airfoil and later GF of various sizes were added on it to understand the change in flow dynamics achieved by adding the GF and their impact on aerodynamic parameters such as Cl, Cd and Cl/Cd. Eppler 423 being a highly cambered airfoil produces high lift coefficient and smoother stall and by adding the GF of various sizes the performance of Eppler 423 improves tremendously and reason for this enhanced performance and effect of size of GF are presented in this paper. Vortex Generators (VG) generate counter rotating vortices that allow the flow to remain attached even at high angles of attack. Also, effect of adding VG at the leading edge of Eppler 423 aerofoil is presented in this paper. At last, results obtained from combination of VG at leading edge and GF at trailing edge on Eppler 423 aerofoil are discussed at length.

Effects of root Gurney flaps on the aerodynamic performance of a horizontal axis wind turbine

This paper presents a computational investigation on the effects of Gurney flaps on the aerodynamic performance of a horizontal axis wind turbine, which is part of the EU FP7 AVATAR project. The research investigates two configurations of Gurney flaps applied at the inboard part of the blade (r/R=0.30∼0.46) at 85% chord location on the pressure surface. The computational method applied in the investigation solves the Reynold-Averaged Navier-Stokes (RANS) equations with multiple reference frame (MRF) approach, which models the rotating turbulent flow over the wind turbine rotor. Numerical simulations are performed for the wind turbine rotor with and without Gurney flap at the tip speed ratios λ=4.59 and 6.35. Comparison of the numerical results with experimental measurements shows that the deployment of Gurney flaps effectively increases the power coefficients of the rotor by 21% at λ=6.35. Gurney flaps have a considerable 3D effect on spanwise thrust and torque coefficients distribution. The performance of two Gurney flaps configurations is compared. It is shown that the larger Gurney flap reduces the effect on the power generated due to protruding out of the local boundary layer of the flow. The numerical results are in good agreement with the experimental results in terms of total thrust and power within 14.1% difference, and complement the experimental database.

Effect of Gurney Flap Geometry on a S809 Airfoil

In this paper, the effect of Gurney flap shapes on wind turbine blade airfoil S809 has been studied by numerical simulation. First, the O-type grid is used in the numerical simulation. By comparing with experimental data, such as the lift force, the drag coefficient, and the pressure distribution, the accuracy of the simulation method is validated. Second, the research on the widths of three kinds of rectangular Gurney flaps at the trailing edge of the S809 airfoil is carried out. Rectangular Gurney flaps can considerably increase the lift in both the linear and nonlinear sections, and the maximum lift coefficient can be increased by 20.65%. In addition, the drag and the pitching moment are increased. However, the width of the rectangular Gurney flap has a small impact on the lift, the drag, and the pitching moment. Finally, the effects of rectangular and triangular Gurney flaps on the aerodynamic characteristics of the S809 airfoil are compared. The results show that the triangular flaps can obtain an increase of maximum lift coefficient by 28.42%, which is better than 16.31% of the rectangular flaps.

Effect of Gurney Flaps on the Aerodynamic Characteristics of NACA 0010 Cascades

Abstract Two dimensional computations were conducted to investigate the performance of NACA 0010 cascades with Gurney Flaps. The cascades with three different stagger angles (βB) viz. 45°, 90° and 135° were studied for the aerodynamic performance characteristics of the blades with and without Gurney Flaps and the results were compared. The Gurney Flap’s length is 2 % of the chord length and has a 45° inclination with respect to the chord line. A significant lift augmentation is observed in all the three blade angle configurations due to the Gurney Flap. In terms of aerodynamic efficiency, it was observed that the presence of Gurney Flap was detrimental when βB = 45°, while the same was highly advantageous when βB = 135°. The streamline visualizations indicated the existence of counter rotating vortex pairs behind the Gurney Flap and that their rate of decay with respect to the Angle of attack was affected by the stagger angle at which the blades were arranged.

Experimental and numerical study on the performance of an axial fan with a Gurney flap

Gurney flap is a miniature lift-enhancement device installed at the airfoil trailing edge and has been successfully applied to fixed wing aircraft and low-speed horizontal wind turbines. In this article, Gurney flap is extended to increase pressure output of a diffusive cascade flow in rotating turbomachinery, which is complicated for its three dimensionalities and diffusive separation characteristics. Wind tunnel tests and computational fluid dynamic simulations were accomplished on an axial fan profiled with an NACA 65-(12)10 airfoil to investigate the effects of Gurney flap on the performance of a high solidity. We present the detailed flow features of the fan with and without Gurney flap after validating the simulation results with the experimental datum. The experimental results show positive Gurney flap effects on fan’s pressure rise and flow rate improvement. However, negative Gurney flap effects on fan’s efficiency are more evident than Gurney flap on isolated airfoils. Detailed flow field analysis from computational fluid dynamic computation reveals that the increased airfoil pressure loading along the fan blade chord strengthens the tip leakage flow, which induces more tip second flow losses than in the baseline fan. In addition to the positive lift enhancement, the net Gurney flap effect in diffusion cascade is influenced by the three-dimensional flow structure.