Gurney Flap Research Articles

Aerodynamic Effect of the Gurney Flap on the Front Wing of a F1 Car and Flow Interactions with Car Components

The design of a racing car needs several aerodynamic design steps in order to achieve high performance. Each component has an aerodynamic interaction with the others and high performance requires a good match between them. The front wing is undoubtedly one of the main components to determine car performance with a strong interaction with the downstream components. The Gurney Flap (GF) is a small appendix perpendicular to the pressure side of the front wing at the trailing edge that can dramatically improve the front wing performance. In the literature, the performance of a GF on a single profile is well documented, while in this paper the GF mounted on the front wing of a racing car has been investigated and the interactions through the 3D flow structures are discussed. The global drag and downforce performance on the main components of the vehicle have been examined by comparing the cases with and without a GF. The GF increases the downforce by about 24% compared to a limited increase in the drag force. A fluid dynamic analysis has been carried out to understand the physical mechanisms of the flow interaction induced to the other components. The GF, in fact, enhances the ground effect, by redistributing the flow that interacts differently with the other components i.e., the wheel zone.

A Numerical Study of Correlation Between Recirculation Length and Shedding Frequency in Vortex Shedding Phenomena

The purpose of this paper is to characterize and to estimate the recirculating length behind an aerodynamic profile in ground effect with Gurney Flap. The flow characterization at high Reynolds numbers was performed by means of numerical analysis. A correlation between the size of the recirculation length and the frequency of vortex shedding was studied. The vortex shedding has a characteristic frequency, which, in this work, is correlated to the size of a recirculation length defined by the authors. The numerical investigation methodology applied to the profile with Gurney Flap, was previously developed on the well-documented test case of the flow around a cylinder at high Reynolds. The case was chosen to investigate and to validate the numerical approach with experimental data.

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.

The influence of gurney flap to the stability of formula car rear wing with simulation

The rear wing on the racing car is used to maintain the vehicle’s stability when driving at high velocity. However, in reality when a racing car runs at high velocity, it does not function optimally because of the maximum limit of compressive force generated. Therefore, modifications of the rear wing are needed to increase the compressive force. The common modification is varying the number and shape of the spoilers or change the angle of attack. This study used a single spoiler variation with the addition of gurney flap attached to the rear wing spoiler. The addition of gurney flap was expected to improve the aerodynamic performance, resulting the greater downforce. This study was conducted with a simulation using Solidwork 2018 student version. The variations applied were rear wings using gurney flap and without gurney flap at velocity of 25 m/s, 50 m/s and 88.89 m/s. The results of the variation of gurney flap addition on the rear wing produced a greater variety of downforce based on the value of the resulting lift coefficient. As velocity increased, the pressure and the coefficient lift were also increased. The effect were the greater the compressive force so as the stability was increased.

Combined Numerical and Experimental Study on the Use of Gurney Flaps for the Performance Enhancement of NACA0021 Airfoil in Static and Dynamic Conditions

Abstract Power augmentation devices in wind energy applications have been receiving increasing interest from both the scientific and the industrial community. In particular, Gurney flaps (GFs) showed a great potential thanks to the passive functioning, the simple construction, and the possibility to add them as a retrofit to existing rotors. Within this context, the authors have performed an extended investigation on the lift increase capabilities of GFs for the well-known NACA 0021 airfoil, which has been used in several wind energy applications up to now. This paper shows the results of a combined experimental and numerical analysis considering different geometrical configurations of the flaps under both static and dynamic conditions. Experimental data were first obtained for the AoA range of 180 degrees at a Reynolds number of 180 k to analyze the impact of three different geometrical configurations of the GF on the aerodynamic behavior. The geometrical configurations were defined by varying the length of the flap (1.4% and 2.5% of the chord) and its inclination angle with respect to the blade chord (90 deg and 45 deg). The experimental investigation involved also dynamic sinusoidal pitching movements at multiple reduced frequencies to evaluate the stall hysteresis cycle. An unsteady computational fluid dynamics (CFD) numerical model was calibrated against wind tunnel data and then exploited to extend the investigation to a wider range of Reynolds numbers for dynamic AoA rates of change typical of vertical-axis wind turbines, i.e., characterized by higher reduced frequencies with a nonsinusoidal motion law.

A Study on Relationship among Blade Camber Direction and Pitch Angle and Performance of a Small Straight-Blade Darrieus Wind Turbine by Using Scale Test Model and Gurney Flap

Straight-blade Darrieus vertical axis wind turbines are used as medium and small size wind turbine because of higher power output in vertical axis wind turbine (VAWT). In our previous study, the relationship between the performance and Reynolds number based on airfoil chord length had been investigated by using small-scale test models of lift-type VAWT, and the results showed that the performance of tested wind turbine models with small diameter was clearly lower than that of the large-scale field test machine, and its performance also varies significantly with the blade pitch angle. In this study, we focused on the performance of a small-scale straight-blade Darrieus VAWT, the relationship among the blade airfoil camber direction and the pitch angle, and the performance of the small-scale VAWT was examined experimentally by using a small-scale VAWT test model with Gurney flap which was a small flat plate. Gurney flaps with its height h, as a ratio to the blade chord length c, h/c = 0.036 to 0.055, were attached to the blades of the VAWT test model, in addition, the attaching direction of the Gurney flap on the blade was examined for both inward and outward of the rotor, and the pitch angle was also examined for a range of −5 to 10 degrees. These results are discussed comparing with the result of the VAWT without Gurney flap and considering the numerical results for the single blade with/without the Gurney flap. The results showed that the performance of the tested VAWT was reversed between the inward and outward Gurney flaps around a pitch angle of 10 degrees. That is, the inward Gurney flap was superior at a pitch angle of less than 10 degrees, while the outward Gurney flap was effective at a pitch angle of more than 10 degrees. Furthermore, for the tested small-scale VAWT model, the optimum pitch angle was about 5 degrees, and the inward and shorter Gurney flap showed higher power performance of the VAWT under this pitch angle condition.

CFD analysis of a Lift-type Vertical Axis Micro Wind Turbine with Gurney Flap

CFD analysis of a Lift-type Vertical Axis Micro Wind Turbine with Gurney Flap

Numerical Investigation of the Benefits of Serrated Gurney Flaps on an Axial Flow Fan

Numerical Investigation of the Benefits of Serrated Gurney Flaps on an Axial Flow Fan

NACA0018翼型锯齿襟翼气动性能的数值研究

NACA0018翼型锯齿襟翼气动性能的数值研究

Aeroelastic vibration analysis of wind turbine blade with Gurney flap

In this paper, based on the parametric design of 3 D blades including typical cross-section and natural frequency calculation of the equivalent model, an integral method for aerodynamic performance and aeroelastic vibration analysis of blade with Gurney flap is proposed. Parametric design and unstructured grid are used to pre-process the blades with/without the Gurney flap. The discrete aerodynamic performance parameters distribution including the lift, drag, and torsion coefficients calculated by Fluent is fitted by the nonlinear least square method based on the trust-region algorithm, and the natural frequencies of the rotating blade are accurately solved by the equivalent thin-walled beam model and Green’s functions. Based on the aerodynamic performance coefficients and natural frequencies obtained by the accurate calculation above, the aeroelastic response equation of typical cross-section considering local aerodynamic damping matrix is established, and the vibration response of blade in flap and torsion direction is further described. From the analysis results, it can be seen that the Gurney flap structure can not only bring higher lift performance to the blade, but also can reduce the amplitude and vibration range of aeroelastic vibration, improve the aeroelastic stability of the blade, and prove the effectiveness of Gurney flap.

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 geometric parameters of Gurney flap on performance enhancement of straight-bladed vertical axis wind turbine

The enhancement of aerodynamic performance of airfoil using Gurney flap was demonstrated and due to its effects of lift increasing and stall suppression on airfoil, Gurney flap has positively functioned in a wide range of engineering. Though there had been numerous scholars who aroused wide concern on geometric parameters of Gurney flap for airfoil, the investigation of geometric design of Gurney flap for straight-bladed vertical axis wind turbine is absent. In current research, a comprehensive numerical study on the effect of geometric parameters of Gurney flap on performance enhancement of straight-bladed vertical axis wind turbine. Before a validation between numerical results and experimental data was carried out, a novel mathematical model of resistance torque of struts was put forward to increase the reliability of numerical model. The results show that the Gurney flap can remarkably promote the aerodynamic performance of vertical axis wind turbine with a decreased rotational velocity. The maximum improvement can reach up to 21.32%. In upstream area, Gurney flap can considerably increase the blade tangential force. Short-Gurney-flap blade can effective weaken the deficiency of aerodynamic loss in downstream area. The 0.75%-chord-length height is most appropriate for the straight-bladed vertical axis wind turbine in this paper. The aerodynamic load with Gurney flap is not sensitive to width. The design with 0.12%-chord-length width is the most suitable value through analyzing the power coefficient curve.

The effect of rectangulargurney flap on wells turbine performance

Wells turbine is very adept at converting pneumatic power from ocean waves into mechanical energy. However, such turbines incur from low performance, limited operating range and low efficiency. The present study introduces a method to enhance the power produced from Wells turbine by implementing rectangular Gurney flap (GF). The Gurney flap is placed on both pressure and suction sides of the trailing edge (TE) and perpendicular to the chord line without change chord length. GF increases the lift coefficient by altering the Kutta condition at the TE. The turbine performance is herein evaluated by solving numerically 3D incompressible Reynolds Averaged Navier–Stokes equations (RANS) by using ANSYS Fluent 19.0. The performance is demonstrated according to the flow coefficient, torque coefficient, total pressure loss coefficient, and the turbine efficiency, as well as the velocity and pressure fields around the turbine blades. The validation of the present work was achieved using previous experimental work and CFD work by using SST k – ω turbulence model. The present work showed that the Wells turbine augmented with GF increases the torque coefficient by 41.98%. Besides, the stall has been delayed compared with the conventional Wells turbine.

Experimental Study on Aerodynamic Characteristics of a Gurney Flap on a Wind Turbine Airfoil under High Turbulent Flow Condition

The objective of the current work is to experimentally investigate the effect of turbulent flow on an airfoil with a Gurney flap. The wind tunnel experiments were performed for the DTU-LN221 airfoil under different turbulence level (T.I. of 0.2%, 10.5% and 19.0%) and various flap configurations. The height of the Gurney flaps varies from 1% to 2% of the chord length; the thickness of the Gurney flaps varies from 0.25% to 0.75% of the chord length. The Gurney flap was vertical fixed on the pressure side of the airfoil at nearly 100% measured from the leading edge. By replacing the turbulence grille in the wind tunnel, measured data indicated a stall delay phenomenon while increasing the inflow turbulence level. By further changing the height and the thickness of the Gurney flap, it was found that the height of the Gurney flap is a very important parameter whereas the thickness parameter has little influence. Besides, velocity in the near wake zone was measured by hot-wire anemometry, showing the mechanisms of lift enhancement. The results demonstrate that under low turbulent inflow condition, the maximum lift coefficient of the airfoil with flaps increased by 8.47% to 13.50% (i.e., thickness of 0.75%), and the Gurney flap became less effective after stall angle. The Gurney flap with different heights increased the lift-to-drag ratio from 2.74% to 14.35% under 10.5% of turbulence intensity (i.e., thickness of 0.75%). However, under much a larger turbulence environment (19.0%), the benefit to the aerodynamic performance was negligible.

Probabilistic neural networks for fluid flow surrogate modeling and data recovery

We consider the use of probabilistic neural networks for fluid flow {surrogate modeling} and data recovery. This framework is constructed by assuming that the target variables are sampled from a Gaussian distribution conditioned on the inputs. Consequently, the overall formulation sets up a procedure to predict the hyperparameters of this distribution which are then used to compute an objective function given training data. We demonstrate that this framework has the ability to provide for prediction confidence intervals based on the assumption of a probabilistic posterior, given an appropriate model architecture and adequate training data. The applicability of the present framework to cases with noisy measurements and limited observations is also assessed. To demonstrate the capabilities of this framework, we consider canonical regression problems of fluid dynamics from the viewpoint of reduced-order modeling and spatial data recovery for four canonical data sets. The examples considered in this study arise from (1) the shallow water equations, (2) a two-dimensional cylinder flow, (3) the wake of NACA0012 airfoil with a Gurney flap, and (4) the NOAA sea surface temperature data set. The present results indicate that the probabilistic neural network not only produces a machine-learning-based fluid flow {surrogate} model but also systematically quantifies the uncertainty therein to assist with model interpretability.

Impacts of Gurney flap and solidity on the aerodynamic performance of vertical axis wind turbines in array configurations

To improve the overall performance of VAWT farm configurations, the impacts of Gurney flap (GF) and the parameter of solidity on the performance of VAWTs in three-turbine arrays are investigated via computational fluid dynamics (CFD) simulations after a validation of computational model using experimental data in the present study. The results indicate that with the tip speed ratio (TSR) of the upstream pairs of VAWTs in array staggered configurations increasing, the flow velocity through the gap is higher and the upstream pairs of VAWTs achieve higher power output at high TSR compared to an isolated turbine. Then, the addition of GF on the upstream pairs of VAWTs can achieve higher flow velocity through the gap compared to the upstream clean coupled VAWTs, which is beneficial to the power output of downstream rotor. The downstream turbine in the configurations which consists of three GF-VAWTs achieves the best aerodynamic performance at TSR < 3.1, and at TSR = 2.51, this downstream rotor enhances the maximum average torque by 36.5% and 24% in comparison with the isolated clean turbine and the isolated GF-turbine respectively. Moreover, the downstream VAWT in array configurations with each solidity obtains higher power extraction than the isolated counterpart at overall TSR. At TSR = 2.27, the downstream rotor with a chord length of 123.5 mm achieves the increment of 23.1% in comparison with isolated counterpart.

On the Performance of Swing Arm Flapping Turbines

Abstract This study investigates the energy extraction mechanism by means of swing arm turbine. The swing arm turbines have a particular motion pattern. The pure translation motion in the conventional flapping turbine changes based on the swing arm rotation. The laminar flow around a NACA0015 is resolved using computational fluid dynamics (CFD) method. The turbine blades are equipped with an oscillating gurney flap for trying to boost the system efficiency. The connected gurney flap oscillates with a given pitching angle. A user-defined function and the sliding dynamic mesh technique available in ansys fluent version 15 are used to adjust both the blade and the flap positions during the turbine flapping cycle. The effects of the swing factor and the flap length on the system performance are provided. It is shown that the suggested strategy of control is able to alter the pressure distribution during both the up stroke and down stroke phases, which changes the blade aerodynamic forces during all the flapping cycle portions and therefore improving the turbine efficiency.

Parametric slat design study for thick-base airfoils at high Reynolds numbers

Abstract. Standard passive aerodynamic flow control devices such as vortex generators and gurney flaps have a working principle that is well understood. They increase the stall angle and the lift below stall and are mainly applied at the inboard part of wind turbine blades. However, the potential of applying a rigidly fixed leading-edge slat element at inboard blade stations is less well understood but has received some attention in the past decade. This solution may offer advantages not only under steady conditions but also under unsteady inflow conditions such as yaw. This article aims at further clarifying what an optimal two-element configuration with a thick main element would look like and what kind of performance characteristics can be expected from a purely aerodynamic point of view. To accomplish this an aerodynamic shape optimization procedure is used to derive optimal profile designs for different optimization boundary conditions including the optimization of both the slat and the main element. The performance of the optimized designs shows several positive characteristics compared to single-element airfoils, such as a high stall angle, high lift below stall, low roughness sensitivity, and higher aerodynamic efficiency. Furthermore, the results highlight the benefits of an integral design procedure, where both slat and main element are optimized, over an auxiliary one. Nevertheless, the designs also have two caveats, namely a steep drop in lift post-stall and high positive pitching moments.

A Note on the Decomposition of Aerodynamic Forces Induced by A Wind Turbine Flaps

ABSTRACTIn this study, the aerodynamic characteristics of a vertical-axis wind turbine blade coupled with a high-lift device, such as the Gurney flap at the trailing edge, are investigated. For numerical analysis, the force element theory is used to understand how the Gurney flap influences the force evolution of the lift-type vertical-axis wind turbine. This study shows that the lift and drag can be respectively approximated into four elements, which are induced by volume vorticity, rotational velocity, angular acceleration and surface friction of the flow around the blades. Based on the perspective of the force element theory, the present simulation provides a clear picture of how the Gurney flap influences the formation of the aerodynamic force elements during a rotational cycle for a vertical-axis wind turbine. Simulation results show that the contributions mainly result from the surface vorticities, the rotational acceleration of the airfoil, and the acceleration of the surface.

Large exit flanges in diffuser-augmented turbines lead to sub-optimal performance

The use of a diffuser enhances turbine performance by augmenting the mass flow rate through the rotor. The use of large annular flanges at the exit of the diffuser has been studied extensively, but the present study shows that large exit flanges lead to sub-optimal performance when considering the power coefficient as defined by the maximum frontal area of the combined diffuser-rotor system (CPtot). Viscous actuator disk simulations are employed to investigate the effect of variable diffuser geometry on performance, and the investigation is divided into two sub-studies. In the first, it is shown that the mass flow rate exhibits a consistent linear relationship to the sectional diffuser lift coefficient, across geometries and rotor thrust coefficients. Since large flanges tend to enhance diffuser thrust more so than sectional lift, their utility is called into question. In the second sub-study, flange height is varied for an otherwise fixed geometry, and it is shown that a flange height of h/Di ​= ​0.04 yields the best performance of CPtot ​= ​0.576. This flange height is much smaller than the flanges typically considered in the literature; it is effectively a Gurney flap, a small trailing edge device known to enhance lift on airfoils.