Gurney Flap Height 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.

Numerical Investigation on J‐Shaped Straight‐Bladed Darrieus Vertical Axis Wind Turbines Equipped with Gurney Flaps

This study provides a numerical investigation about J‐shaped straight‐bladed Darrieus vertical axis wind turbines equipped with outboard, inboard, and two‐sided Gurney flap (GF). The performance of the turbines is examined for different GF heights and tip speed ratios (TSRs). The aerodynamic analysis is carried out using power curves, vorticity field, and pressure field surrounding the wind turbine. The results indicate that employing the inboard GF effectively enhances the turbine’s performance by harnessing the drag force in the desired direction and postponing the flow separation up to 14° of azimuth angle. The inboard GF with a height of 0.75% chord length exhibits the best performance among the GFs, showing an increase in output power at higher TSRs up to 12.35%. Conversely, the use of outboard and two‐sided GFs of any height cannot improve the turbine efficiency.

Aerodynamic Characteristics of Ahmed Body with Inverted Airfoil Eppler 423 and Gurney Flap on Fastback Car

The installation of aerodynamic devices, such as rear wings with the application of a Gurney flap, is very important to improve the performance of vehicles and can generate downforce and reduce slip when a car turns and brakes. The goal of this study was to determine the aerodynamic characteristics of the addition of a rear wing using an Eppler 423 airfoil, which was applied with a Gurney flap featuring variations in the angle of attack and the height of the Gurney flap. The rear wing was mounted on the Ahmed body with a rear slant angle of 15°, which is similar to the configuration on a fastback type car. This research was conducted by 3D modeling through computational fluid dynamics (CFD) simulation using ANSYS Student R18.2 by using ahmed body design. There are three variations in the angle of attack for the rear wing (0°, 7.5°, and 15°), as well as five variations in Gurney flap height of 0%, 0.5%, 1%, 1.5%, and 2% for the chord-line length. In this study, the best variation was found at an angle of attack of 15⁰ with a height of 2% C. From this configuration improved CL/CD ratio by 25.36% when compared to the results without a Gurney flap.

Numerical Investigation of Aerodynamic Characteristics of Supercritical RAE2822 Airfoil with Gurney Flap

Gurney flap (GF) is well-known as one of the most attractive plain flaps because of the simple configuration and effectiveness in improving the lift of the airfoil. Many studies were conducted, but the effects of GF on the various airfoil types need to be further investigated. This study aimed to clarify the effect of GF in the case of the supercritical airfoil RAE2822. This research includes a steady, two-dimensional computational investigation carried out on the supercritical airfoil type RAE-2822 to analyze Gurney flap (GF) effects on the aerodynamic characteristics of this type of airfoil utilizing the Spalart-Allmaras turbulence model within the commercial software Fluent. The airfoil with the Gurney flap was analyzed for three different height values 1%c, 2%c, and 3%c, and five mounting angles (30°,45°,60°,75°, and 90°) with the axial chord for angles of attack (-1°,-2°,-3°,0°,1°,2°,3°). The calculations showed that when GF height is increased, the maximum suction pressure on the upper surface increases by 25.4%, 36.5%, and 68.83% when the height of the Gurney flap is 1%c, 2%c, and 3%c, respectively, compared with that on the airfoil without GF. The lift coefficient was also increased, and the shock waves moved downward by increasing GF height. As Gurney flap heights increase, the drag coefficient increases gradually for positive angles of attack but for negative angles of attack. The drag coefficient also decreases with increasing the GF heights. As long as the angle of the mounting is between 45o and 90o, the lift coefficient does not differ on a large scale. For mounting angles less than 45o, the lift coefficient drops quite fast. As a result, reducing the Gurney flap’s lift enhancement and the drag coefficient increases gradually for positive angles of attack, but for negative angles, it can be noted that the drag coefficient decreases with increasing the mounting angles of GF. The calculated values of the lift and drag coefficients with an attack angle and pressure coefficient compared with the experimental values, and a good agreement was noticed.

Lift Enhancement of Tiltrotor Wing Using a Gurney Flap

A numerical investigation was undertaken to explore the lift-enhancing characteristics of the Gurney flap on a tiltrotor wing. The heights of Gurney flaps range from 1 to 4% wing chord lengths. The Navier-Stokes equations with the Spalart-Allmaras turbulence model were solved to simulate the flow structure around the Gurney flap. The computational results show that the presence of the Gurney flap can dramatically improve the tiltrotor wing lift coefficient. Compared with the baseline configuration, the maximum lift coefficient is increased by 10.67, 15.33, and 20.67% for the 1, 2, and 4% height Gurney flaps. On the other hand, the Gurney flap also results in a drag penalty, and the overall effect on the wing lift-to-drag is detrimental. In particular, at an angle of attack of 2°, use of a 4% chord length Gurney flap decreases the lift-to-drag ratio by 31.47%. Further studies demonstrate that the wing lift increments are proportional to the square root of the Gurney flap height.

Effect of Gurney flap Height and Mounting Position on the Performance of a Centrifugal Fan

The effect of Gurney flap height and mounting position on the head coefficient of a centrifugal fan at different Reynolds numbers is investigated experimentally. Quarter round Gurney flap of 1.0, 1.5, 2.0 and 2.5 mm height is mounted at three different positions, S=1.00 (impeller tip), S=0.95 and S=0.90 on the pressure surface of the impeller blade tip. Performance tests are carried out on the centrifugal fan at five Reynolds numbers corresponding to five rotational speeds of 1100, 1500, 2000, 2500 and 2900 rpm respectively. From the performance curves it is found that the fan head coefficient increases significantly with Gurney flaps at low Reynolds numbers and increases marginally at high Reynolds numbers. Effect of Reynolds number on the head coefficient is considerable for the baseline fan and found to be negligible for the fan with Gurney flaps, for all combinations of Gurney flap mounting position and height. The head coefficient of the fan improves as Gurney flap height increases but the improvement is marginal after certain height of Gurney flap. The head coefficient of the fan deteriorates when Gurney flap is mounted away from the impeller blade tip.

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.

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.

Dynamic stall of an airfoil with different mounting angle of gurney flap

PurposeOne of the best methods to improve wind turbine aerodynamic performance is modification of the blade’s airfoil. The purpose of this paper is to investigate the effects of gurney flap geometry and its oscillation parameters on the pitching NACA0012 airfoil.Design/methodology/approachThis numerical solution has been carried out for different cases of gurney flap mounting angles, heights, reduced frequencies and oscillation amplitudes, then the results were compared to each other. The finite volume method was used for the discretization of the governing equations, and the PISO algorithm was used to solve the equations. Also, the “SST” was adopted as the turbulence model in the simulation.FindingsIn this paper, the different parameters of gurney flap were investigated. The results showed that the best range of gurney flap height are between 1 and 3.2% of chord and the best ratio of lifting to drag coefficient is achieved in gurney flap with an angle of 90° relative to the chord direction. The dynamic stall angle of the airfoil with gurney flap decreases were compared to without gurney flap. Earlier LEV formation can be one of the main reasons for decreasing the dynamic stall angle of the airfoil with gurney flap. Increasing the reduced frequency and oscillation amplitude causes rising of maximum lift coefficient and consequently lift curve slope. Moreover, gurney flap with mounting angle has a lower hinge moment than the gurney flap without mounting angle but with the same vertical axis length. So, there is more complexity in structural design concerning the gurney flap without mounting angle.Practical implicationsImproving aerodynamic efficiency of airfoils is vital for obtaining more output power in VAWTs. Gurney flaps are one of the best mechanisms to increase the aerodynamic performance of the airfoil and increases the efficiency of VAWTs.Originality/valueInvestigating the hinge moment on the connection point of the airfoil, gurney flap and try to compare the gurney flap with and without angle.

Aerodynamic Investigations on SC-0414 Airfoil with Small High Lift Devices

Gurney flap (GF) is well-known that one of the most attractive plain flaps because of the simple configuration and actually effective in improving lift of the airfoil. Many studies were conducted but the effects of GF on the various airfoil types need to be further investigated. This study aimed to clarify the effect of GF in case of the Supercritical airfoil, SC-0414 airfoil. The Ansys Fluent software is used to perform the flow simulations. The result in airfoil baseline is compared with the experiment result obtaining from wind tunnel testing. The flow simulations focus on analyzing the lift coefficient when increasing the height of Gurney flaps. The velocity of the simulations, as well as the experiment is U = 12 m/s and the Reynolds number Re is 1.6 × 105. In the smoke wind tunnel, the flow field are clearly observed by smoke lines. The lift coefficient results of the flow simulations show the similar qualitative trend as the conventional airfoil model with Gurney flap.

Influence of Gurney flaps on aerodynamic characteristics of a canard-configuration aircraft

Purpose The purpose of this paper is to mount Gurney flaps at the trailing edges of the canards and investigate their influence on aerodynamic characteristics of a simplified canard-configuration aircraft model. Design/methodology/approach A force measurement experiment was conducted in a low-speed wind tunnel. Hence, the height and shape effects of the Gurney flaps on the canards were investigated. Findings Gurney flaps can increase the lift and pitching-up moment for the aircraft model tested, thereby increasing the lift when trimming the aircraft. The dominant parameter to influence aerodynamic characteristics is the height of Gurney flaps. When the flap heights are the same, the aerodynamic efficiency of the triangular Gurney flaps is higher than that of the rectangular ones. Moreover, the canard deflection efficiency will be reduced with Gurney flaps equipped, but the total aerodynamic increment is considerable. Practical implications This paper helps to solve the key technical problem of increasing take-off and landing lift coefficients, thus improving the aerodynamic performance of the canard-configuration aircraft. Originality/value This paper recommends to adopt triangular Gurney flaps with the height of 3 per cent chord length of the canard root (c) for engineering application.

The effects of Gurney flap on the aerodynamic performance of NACA 0012 airfoil in the rarefied gas flow

In this research, the rarefied gas flow around the NACA 0012 airfoil with attached Gurney flap at Mach number 2 and three different Knudsen numbers (0.026, 0.1 and 0.26) are studied, numerically. The effects of angle of attack and Gurney flap height on the aerodynamic characteristic of airfoil are investigated. At Kn = 0.026 the flow is simulated using Navier–Stokes equations with slip boundary conditions and DSMC method. In two other Kn numbers only the DSMC method is applied. For the clean airfoil, the calculated lift and drag coefficients and surface pressure distribution are compared with previous studies including the experimental and numerical results. This validation reveals that in the case of clean airfoil, there are a good agreement between the results of this study and those presented in literature. Furthermore, the effects of Gurney flap height on the lift and drag coefficients at different Knudsen numbers and angles of attack are studied. The results shows that for angles of attack smaller than 30°, the Gurney flap can improve the aerodynamics characteristics of airfoil. But, for angles of attack larger than 30° the Gurney flap does not have destructive effect on the aerodynamic characteristics.

NUMERICAL INVESTIGATION FOR THE ENHANCEMENT OF THE AERODYNAMIC CHARACTERISTICS OF AN AEROFOIL BY USING A GURNEY FLAP

Numerical investigation was carried out to determine the effect of a Gurney Flap on NACA 0012 aerofoil performance with emphasis on Unmanned Air Vehicles applications. The study examined different configurations of Gurney Flaps at high Reynolds number of Re=3.6×〖10〗^5 in order to determine the optimal configuration. The Gurney flap was tested at different heights, locations and mounting angles. Compared to the clean aerofoil, the study found that adding the Gurney Flap increased the maximum lift coefficient by19%, 22%, 28%, 40% and 45% for the Gurney Flap height of 1%C, 1.5%C, 2%C, 3%C and 4%C respectively, C represents the chord of the aerofoil. However, it was also found that increasing the height of the gurney beyond 2%C leads to a decrease in the overall performance of the aerofoil due to the significant increase in drag penalty. Thus, the optimal height of the Gurney flap for the NACA 0012 aerofoil was found to be 2%C as it improves the overall performance of the aerofoil by 21%. As for the location, it was found that the lifting-enhanced effect of the gurney flap decreases as it is shifted towards the leading edge. Thus the optimal location of the Gurney Flap mounting was found to be at the trailing edge or at distances smaller than 10%C. The Gurney flap was also tested at different mounting angles of -45, 90 and +45 degrees and it was found that the Gurney flap at +45 mounting angle leads to the optimal performance of the aerofoil.

Numerical investigation into energy extraction of flapping airfoil with Gurney flaps

A new type of Gurney flap is applied for energy extraction enhancement of a flapping airfoil. Two-dimensional Navier-Stokes simulations at Re = 104 are conducted to study the effect of Gurney flaps with various heights. The investigations are undertaken over a wide range of kinematic parameters (reduced frequency k, pitching amplitude θ0). Numerical results show that the application of a Gurney flap notably increases the maximum output power and efficiency compared with a clean NACA0012 airfoil. By affecting the flow structure and the pressure distribution around the trailing edge of the airfoil, the Gurney flap is beneficial to the lift force generation, thus leading to a higher power coefficient. The maximum power coefficient increases with Gurney flap height hg at first between hg = 0c–0.3c (c is the airfoil chord length), while a further increase in hg provides no further energy extraction enhancement. Besides, the increasing hg results in stronger trailing edge vortices and higher drag force.

Numerical investigation of plasma actuated and non-actuated Gurney flaps on aerodynamic characteristics of a plunging airfoil

Two-dimensional laminar incompressible flow around a National Advisory Committee for Aeronautics 0012 plunging airfoil with different Gurney flap heights of 2% C, 5% C, and 7% C and the oscillation amplitude of h = 0.12 C and frequencies of ω = 1.3 and 4.67 rad/s at Re = 1850 is carried out in this paper. In addition to the Gurney flap, in order to control the flow over the airfoil, dielectric-barrier discharge plasma actuator is attached to the flap and its impact is investigated on the aerodynamic coefficients. Flow field and aerodynamic characteristics are compared with the clean plunging airfoil. For the Plasma force considered in this study, the 2% C Gurney flap height lead to a more enhancement in the lift curve. The results indicate that at all actuated and non-actuated Gurney flap heights the thrust is reduced. Furthermore, it is observed that by using plasma force at lower frequencies, [Formula: see text] is proportional to the square root of the Gurney flap height while at higher frequencies, plasma actuation inverses this proportion. Also, it can be concluded that the proportionality factor increases with increasing the frequency for both lifts and drags coefficients.

Pitching Airfoil with Combined Gurney Flap and Unsteady Trailing-Edge Flap Deflection

b = semispan c = airfoil chord Cl = lift coefficient Cm = pitching moment coefficient Cp = surface pressure coefficient f = oscillation frequency h = Gurney flap height td = flap actuation duration ts = flap actuation start time u1 = freestream velocity = angle of attack ds = dynamic-stall angle f = final angle i = initial angle ss = static stall angle = f i, pitch amplitude t = total airfoil pitch time max = maximum flap deflection = fc=u1, reduced frequency

Numerical Simulation of Gurney Flap on RAE-2822 Supercritical Airfoil

A two-dimensional steady Reynolds-averaged Navier–Stokes equation was solved to investigate the effects of a Gurney flap on RAE-2822 (Royal Aeronautical Establishment) supercritical airfoil aerodynamic performance. The heights ofGurneyflaps range from0.25 to 3%airfoil chord lengths. The incompressible/compressibleNavier–Stokes equations were used to simulate the flow structure around the airfoils in subsonic/transonic flows, respectively, with the Spalart–Allmaras turbulence model. In comparison with the clean airfoil, the Gurney flap can significantly increase the prestall lift and lift-to-drag ratio of an RAE-2822 airfoil at a small angle of attack. Nosedown pitching moment also increased with the Gurney flap height. At both takeoff-and-landing status and cruise phase, the aerodynamic performance of the airfoil was significantly improved byGurney flaps with the height below 1%airfoil chord length. In addition, the surface pressure distribution, wake flow velocity profile, and trailing-edge flow structure of the airfoil were illustrated, which helps to understand the mechanisms of the Gurney flap to improve RAE-2822 airfoil aerodynamic performance.

Combined Plasma and Gurney Flap Flow Control at Low Flight Reynolds Numbers

CXXGYY = specification for camber c (XX%) and h=c (YY%) Cl = airfoil lift coefficient, l=q1c Cd = airfoil drag coefficient, d=q1c c = chord length hc i = oscillatory momentum coefficient F = dimensionless unsteady modulation frequency, fmc=U1 f = plasma actuation frequency fm = plasma modulation frequency h = Gurney flap height normal to surface q1 = dynamic pressure Re = Reynolds number, U1c= U1 = freestream velocity = angle of attack = boundary-layer thickness = aerodynamic efficiency, Cl=Cd