Wingtip Devices Research Articles

Geometry optimization studies on nonplanar wingtip devices for typical transport aircraft

Wings are the main lift generating sources for an aerospace system. Wing design is a complex process that involves selection of many aerofoil design parameters, wing design requirements and considerations. The main focus in this study is to validate nonplanar wingtip design methodologies and make a numerical estimation and comparison of aerodynamic characteristics of non planar wing tip devices and the associated induced drag. Naturally the high pressure on the bottom surface of the wing causes streamlines from underneath the wing to wrap around the tip to the top, thereby equalizing the pressure difference at the tip. This creates the rotating flow commonly known as a wing tip vortex. The current study investigates and assesses the possibility of retrofitting a non planar wing tip device for the rectangular tapered wing configuration without adding any additional weight to the main wing structure. There are basically three case studies. The first one is a validation of predicted experimental data against numerical simulation using FLUENT® tool for classical NACA 23015 aerofoil.The second one involves taking into consideration possible mounting location of the nonplanar wingtip device on the main wing for smooth operation and gradual lift generation process.A third case study is comparison of ‘wing alone experimental data’ against ‘wing with nonplanar winglet’data computed using FLUENT® in three dimensional space. Additionally estimation of numerical optimum load distribution is done for one of the optimum nonplanar winglet geometry using MATLAB tool. Finally comparison of MATLAB results with experimental loading is done for clarity.

A CFD Analysis of Wingtip Devices to Improve Lift and Drag Characteristics of Aircraft Wing

The present study investigates the use of various wingtip devices to analyse the parameters of lift and drag for an aircraft wing. The coefficients of lift and drag are investigated in this research to optimize the wing design for enhancing the aircraft performance. A reduction in the drag produced due to wingtip vortices leads to reduced fuel consumption which contributes to the reduction in fuel emissions. The two-dimensional analysis is carried out for the selection of an apposite aerofoil by comparing the lift/drag characteristics of NACA 0012, 2415 and 23015 respectively at the velocity of 79.16 m/s at the angles of attack of 0°,4°,8°,12°,16° and 20°. The aerofoil section NACA 2415 is used to design the three-dimensional aircraft wing. For the analysis of the various wing tip devices the three-dimensional wing is incorporated with the spiroid winglet, blended winglet, wingtip fence and a mini-winglet. The CFD analysis for the wing designs is carried out for the take-off and landing phases of an aircraft’s flight because the effect of vortices is the highest during these flight phases. The angles of attack range from 0° to 20°. The CFD results reveal that for the wing designs, the plain wing produced the highest drag and the blended winglet proved to be the wingtip device with the most beneficial design. The results obtained for the 30° cant angled blended winglet and 60° cant angled wingtip fence produces additional lift when compared to the results obtained for the counterpart designs. The results obtained from the analysis are in close correlation to the established use of the wingtip devices.

Conceptual Design and Performance Optimization of a Tip Device for a Regional Turboprop Aircraft

An increasing number of aircraft is equipped with wing tip devices, which either are installed by the aircraft manufacturer at the production line or are retrofitted after the delivery of the aircraft to its operator. The installation of wing tip devices has not been a popular choice for regional turboprop aircraft, and the novelty of the current study is to investigate the feasibility of retrofitting the British Aerospace (BAe) Jetstream 31 with an appropriate wing tip device (or winglet) to increase its cruise range performance, taking also into account the aerodynamic and structural impact of the implementation. An aircraft model has been developed, and the simulated optimal winglet design achieved a 2.38% increase of the maximum range by reducing the total drag by 1.19% at a mass penalty of 3.25%, as compared with the baseline aircraft configuration. Other designs were found to be more effective in reducing the total drag, but the structural reinforcement required for their implementation outweighed the achieved performance improvements. Since successful winglet retrofit programs for typical short to medium-range narrow-body aircraft report even more than 3% of block fuel improvements, undertaking the project of installing an optimal winglet design to the BAe Jetstream 31 should also consider a direct operating cost (DOC) assessment on top of the aerodynamic and structural aspects of the retrofit.

English

English

Optimal wingtip device design for transport airplane

PurposeThe present work aims to analyze the feasibility of wingtip device incorporation into transport airplane configurations considering many aspects such as performance, cost and environmental impact. A design framework encompassing optimization for wing-body configurations with and without winglets is described and application examples are presented and discussed.Design/methodology/approachmodeFrontier, an object-oriented optimization design framework, was used to perform optimization tasks of configurations with wingtip devices. A full potential code with viscous effects correction was used to calculate the aerodynamic characteristics of the fuselage–wing–winglet configuration. MATLAB® was also used to perform some computations and was easily integrated into the modeFrontier frameworks. CFD analyses of transport airplanes configurations were also performed with Fluent and CFD++ codes.FindingsWinglet provides considerable aerodynamic benefits regarding similar wings without winglets. Drag coefficient reduction in the order of 15 drag counts was achieved in the cruise condition. Winglet also provides a small boost in the clean-wing maximum lift coefficient. In addition, less fuel burn means fewer emissions and contributes toward preserving the environment.Practical implicationsMore efficient transport airplanes, presenting considerable lower fuel burn.Social implicationsAmong other contributions, wingtip devices reduce fuel burn, engine emissions and contribute to a longer engine lifespan, reducing direct operating costs. This way, they are in tune with a greener world.Originality/valueThe paper provides valuable wind-tunnel data of several winglet configurations, an impact of the incorporation of winglets on airplane design diagram and a direct comparison of two optimizations, one performed with winglets in the configuration and the other without winglets. These simulations showed that their Pareto fronts are clearly apart from each other, with the one from the configuration with winglets placed well above the other without winglets. The present simulations indicate that there are always aerodynamic benefits present regardless the skeptical statements of some engineers. that a well-designed wing does not need any winglet.

Numerical and Experimental Study on Performance Enhancement of Darrieus Vertical Axis Wind Turbine With Wingtip Devices

Darrieus type vertical axis wind turbines (VAWT) are being used commercially nowadays; however, they still need to improve in terms of performance as they work in an urban environment where the wind speeds are low and the gusts are frequent. The aerodynamic performance of Darrieus turbine is highly affected by the wingtip vortices. This paper attempts at analyzing and comparing the performance of Darrieus with the use of various wingtip devices. Attempts have also been made to find out optimal working parameters by studying the flow through turbines with different tip speed ratios and different inlet wind speeds. A comparative computational fluid dynamics (CFD) simulation was performed on a small-scale, straight-bladed Darrieus rotor vertical axis wind turbine, with a large stationary domain and a small rotating subdomain using sliding mesh technique. Comparison of the performance of end tip device that can be used against a baseline rotor configuration is done, with the aim of identifying the best tip architecture. The main focus lies on building an experimental setup to validate the results obtained with the CFD simulation and to compare the performance with and without wingtip device. VAWTs with wingtip device show very promising results compared to the baseline model.

Definition of Wingtip Devices Shape and Dimensions for a Subsonic Airliner

The results of flow field numerical simulation on the typical wing-body prototype of the modern DLR-F4 airliner under sub- and transonic compressible air flow are presented. Using the DLR-F4 CAD model, the effect of the wingtip end plate area and of the cant angle of a typical Whitcomb winglet is studied. The dependencies of the model lift-to-drag ratio increment on the flat wingtip end plate relative area and on the cant angle of an airfoil Whitcomb winglet are obtained. The concept of an elliptic winglet with a variable cant angle that similar to the winglet used on Airbus A350 is studied. A technique is developed for solving the multi-parameter design optimization task for the Whitcomb winglet, taking the maximum lift-to-drag ratio of the wing as a criterion for optimization.

Testing of a Hinged Wingtip Device for Gust Loads Alleviation

Recent aircraft designs have considered higher-aspect-ratio wings to reduce induced drag for improved fuel efficiency; however, to remain compliant with airport gate requirements, folding wingtips have been introduced as a solution to the increased wingspan. Recent numerical studies suggest that a folding wingtip solution may be incorporated with spring devices to provide an additional gust loads alleviation ability in flight as well. In this work, a series of low-speed steady and dynamic wind tunnel tests was conducted using a prototype of such a concept. It was found that a folding wingtip with a nonzero relative angle of the folding hinge axis to the streamwise direction could provide gust loads alleviation. The level of load alleviation varied with hinge spring stiffness and lifting condition, with the best performance achieving a 56% reduction in peak loading.

Bioinspired wingtip devices: a pathway to improve aerodynamic performance during low Reynolds number flight

Birds are highly capable and maneuverable fliers, traits not currently shared with current small unmanned aerial vehicles. They are able to achieve these flight capabilities by adapting the shape of their wings during flight in a variety of complex manners. One feature of bird wings, the primary feathers, separate to form wingtip gaps at the distal end of the wing. This paper presents bio-inspired wingtip devices with varying wingtip gap sizes, defined as the chordwise distance between wingtip devices, for operation in low Reynolds number conditions of Re = 100 000, where many bird species operate. Lift and drag data was measured for planar and nonplanar wingtip devices with the total wingtip gap size ranging from 0% to 40% of the wing’s mean chord. For a planar wing with a gap size of 20%, the mean coefficient of lift in the pre-stall region is increased by 7.25%, and the maximum coefficient of lift is increased by 5.6% compared to a configuration with no gaps. The nonplanar wingtip device was shown to reduce the induced drag. The effect of wingtip gap sizes is shown to be independent of the planarity/nonplanarity of the wingtip device, thereby allowing designers to decouple the wingtip parameters to tune the desired lift and drag produced.

IMPROVING THE AERODYNAMICS OF A TRANSPORT AIRCRAFT WING USING A DELTA PLANFORM WINGTIP LEADING EDGE EXTENSION

The article explores the possibility of improving the aerodynamic properties of a supercritical-airfoil wing, typical for a modern passenger aircraft, using delta planform passive devices of large relative areas, installed along the leading edge at the wing tip. Delta extensions of various configurations were considered to be used as wingtip devices, potentially improving or completely replacing classical R. Whitcomb winglets. As a result of two- and three-dimensional CFD simulations performed on DLR-F4 wing-body prototype, the potential advantage of these devices was confirmed, particularly when they are installed in a combination with an elliptical planform, largely swept, raked winglet in terms of reducing the induced drag and increasing the aerodynamic lift-to-drag ratio at flight angles of attack. The growth in lift-to-drag ratio applying these devices owes it solely to the drop in drag, without increasing the lift force acting on the wing. In comparison to the classical winglets that lead to a general increase in lifting and lateral forces acting on the wing structure, resulting in a weight penalty, the Wingtip Ledge Edge Triangular Extension (WLETE) yields the same L/D ratio increase, but with a much smaller increase in the wing loading. A study has been made of the characteristics of the local (modified) airfoil in the WLETE zone in a two-dimensional flow context, and a quantitative analysis has been conducted of the influence of WLETE on both the profile and induced drag components, as well as its influence on the overall lift coefficient of the wing. The resulted synthesis of the WLETE influence on the wing L/D ratio will consist of its influence on each of these components. A comparison of the efficiency of using delta extensions against classical winglets was carried out in a multidisciplinary way, where in addition to the changes in aerodynamic coefficients of lift and drag, the increments of magnitude and distribution of the loads acting on the wing console were studied along with the maximum resulted structural stress. The study of the growth of structural stress on the wing structure after installing WLETE, confirmed the results obtained from CFD simulations that these delta extensions do not increase and do not change the distribution of total forces and moments acting on the wing console.

Compliant structures based on stiffness asymmetry

ABSTRACTOne of the key problems in the development of morphing aircraft is the morphing structure, which should be able to carry loads and change its geometry simultaneously. This paper investigates a compliant structure, which has the potential to change the dihedral angle of morphing wing-tip devices. The compliant structure is able to induce deformation by unsymmetrical stiffness allocation and carry aerodynamic loads if the total stiffness of the structure is sufficient.The concept has been introduced by building a simplified model of the structure and deriving the analytical equations. However, a properly designed stiffness asymmetry, which is optimised, can help to achieve the same deformation with a reduced actuation force.In this paper, round corrugated panels are used in the compliant structure and the stiffness asymmetry is introduced by changing the geometry of the corrugation panel. A new equivalent model of the round corrugated panel is developed, which takes the axial and bending coupling of the corrugated panel into account. The stiffness matrix of the corrugated panel is obtained using the equivalent model, and then the deflections of the compliant structure can be calculated. The results are compared to those from detailed finite element models built in the commercial software Abaqus. Samples with different geometries were manufactured for experimental tests.After verifying the equivalent model, optimisation is performed to find the optimum geometries of the compliant structures. The actuation force of a single compliant structure is first optimised, and then the optimisation is performed for a compliant structure consisting of multiple units. A case study is used to show the performance improvement obtained.

Yatay Kuyruklarda Kıvrık Kanat Ucu Kullanımının Aerodinamik Etkileri

In this study, aerodynamic forces on a horizontal stabilizer of commercial aircraft that has NACA 0012 airfoil and new horizontal stabilizers that are designed by mounting two different curved wingtip devices (winglet) to the preliminary horizontal stabilizer at different angle of attack values. The preliminary horizontal stabilizer is designed by the airfoil shape that is composed of 200 points and determined span, root chord, dihedral angle, sweep angle and taper ratio values. This design is defined as C 1 . Two curved wingtip devices that have the same sweep angle, cant angle, taper ratio, span and height but different airfoil thickness ratio at tip are designed and mounted to the C 1 . These are named as C 2 and C 3 , respectively. The aerodynamic analyses of these designs are done by using Fluent that is a well-known computational fluid dynamics program. The analyses are performed at 13 different angle of attack values and the alterations on drag (C D ) and lift (C L ) coefficients of the designed horizontal tails are observed. According to the results, C 2 has higher lift to drag ratio (C L /C D ) values at all angle of attack values. For the C 3 design, the same result has been seen except for the result of -1 degree angle of attack.

An analysis on Aerodynamics Performance Simulation of NACA 23018 Airfoil Wings on Cant Angles

Winglet attached on the tip of aircraft wings to increase lift. Mainly, winglet used for increasing aerodynamic efficiency, it decreases induced drag caused by vortex on wings tip. The phenomenon of vortex is collision of high-pressured air below the wings meet the low-pressured air above it that cause turbulence. Induced drag may reach 40% of total drag during cruising, and 80-90% while take off. A procedure to decrease induced drag is using wing tip devices. It used on commercial aircrafts and the most frequently used is blended winglet. Numerical study conducted to examine the best aerodynamic performance of sub-sonic plane wings in angles of attack. Analysis on NACA 23018 airfoil wings with blended winglet on the tip was conducted. Freestream velocity of 40 m/s or Re = 1 × 106, and angle of attack (α) 0o, 5o, 10o, and 15o are used. Evaluation for parameter includes coefficient pressure (Cp), velocity profile, lift, drag, and ratio CL/CD. Obtained contour are pressure contour, velocity, and vorticity. In view of all this, there is increasing performance of aerodynamic with CL/CD ratio of wings with blended winglet and plain wing. Reaching current angle of attack, the function of winglet is gradually decrease.

Generation Mechanism and Reduction Method of Induced Drag Produced by Interacting Wingtip Vortex System

AbstractThe formation and evolution of wingtip vortex system generated from three wing configurations are simulated with the improved delayed detached eddy simulation (IDDES) method. Numerical results show that each layout produces an interacting wingtip vortex system. These three corresponding vortical interactions are, respectively, the interaction between wingtip vortex and its counter-rotating vortex, winglet-tip vortex, and winglet four-vortex system. The fluid entrainment of ambient fluid and vortical impulse transport resulted from inductive effect have been founded generally existing in its formation and evolution. These two dominated mechanisms account for induced drag generation. On one hand, the winglet with toed-out angle is considered capable of changing the flow field around the winglet, and decomposing the winglet-tip vortex into four small vortices. Due to quite few fluid entrainment effects, this typical four-vortex system that cannot merge and only dissipate in the near wake scarcely contributes to the induced drag. On the other hand, a potential drag reduction method is also indicated that a lower induced drag can be obtained when the merger of wingtip and winglet-tip vortex is controlled and eliminated. This investigation will offer a novel perspective to guide the design of wingtip device and method of crusing resistance reduction for aircrafts.

Developing of Balancing Tools for Flight Controls

Wingtip devices may be fitted for various reasons, they often combine more than one function and usually occupy a substantial part of the stabilizer, just belong the aileron spar. Winglets allow decreasing fuel consumption of over 10%. But with the development of new generations of aircraft, it is not always appropriate to take into account the stability and controllability of the flight. Because there is a need to improve the existing designs in the paper proposed new concept of winglets.

Preliminary investigation of use of flexible folding wing tips for static and dynamic load alleviation

ABSTRACTA recent consideration in aircraft design is the use of folding wing-tips with the aim of enabling higher aspect ratio aircraft with less induced drag while also meeting airport gate limitations. This study investigates the effect of exploiting folding wing-tips in flight as a device to reduce both static and dynamic loads. A representative civil jet aircraft aeroelastic model was used to explore the effect of introducing a wing-tip device, connected to the wings with an elastic hinge, on the load behaviour. For the dynamic cases, vertical discrete gusts and continuous turbulence were considered. The effects of hinge orientation, stiffness, damping and wing-tip weight on the static and dynamic response were investigated. It was found that significant reductions in both the static and dynamic loads were possible. For the case considered, a 25% increase in span using folding wing-tips resulted in almost no increase in loads.

Nonlinear Folding Wing Tips for Gust Loads Alleviation

A recent consideration in aircraft design is the use of folding wing tips with the aim of enabling higher aspect ratio aircraft with less induced drag, but also meeting airport gate limitations. This study builds on previous work investigating the effect of exploiting folding wing tips in-flight as a device to reduce dynamic gust loads, but now with the introduction of a passive nonlinear hinge spring to allow wing-tip deflections only for larger load cases. A representative civil jet aircraft aeroelastic model is used in a multibody simulation code to explore the effect of introducing such a hinged wing-tip device on the loads behavior. It was found that significant reductions in the dynamic loads were possible.

NUMERICAL INVESTIGATION OF WINGLET ANGLES INFLUENCE ON VORTEX SHEDDING

Wingtip devices are usually intended to improve the efficiency of fixed-wing aircraft. There are several types of wing tip devices, and although they function in different manners, the intended effect is always to reduce the aircraft's drag by partial recovery of the tip vortex energy. Wingtip devices can also improve aircraft handling characteristics and enhance safety for following aircraft. Such devices increase the effective aspect ratio of a wing without materially increasing the wingspan. The purpose of this project is to analyse different types of winglets using Auto CAD, GAMBIT and FLUENT and then, to find out what happens when winglets are linked to wingtips and to study about the aerodynamic properties of spiroid winglets which are still under research. One wing model without winglet and three wing models with winglets were created and drawn in Auto CAD and they were meshed in GAMBIT using geometry data gathered from research papers. Those models were read into Fluent where flow boundary conditions were applied. The wing without winglet, the wings with spiroid winglets and the wings with other kinds of winglets performance were analyzed in several angles of attack and the drag coefficient was compared when the aircraft is taking off. Wingtip vortices from models were checked, studied and compared. The best winglet model reduces drag coefficient and wingtip vortices from wing without winglet model and it will be pointed out at the end of this project. --------------------------------------------------------------------***----------------------------------------------------------------------

Multi-Element Winglets: Multi-Objective Optimization of Aerodynamic Shapes

The wing tip device in this study was to mimic the wing tips of a soaring bird, featuring three smoothly blended elements. Each such multi-element winglet was integrated into a complete wing–tail–body aircraft configuration. The geometry of each of the three elements in the multi-element winglet was defined using 11 parameters, totaling 33 parameters for a complete multi-element winglet geometry. This design methodology used a three-dimensional geometry generation algorithm based on locally analytical smoothly connected surface patches, allowing for the creation of vastly diverse three-dimensional geometries with a minimal number of specified design parameters. A three-dimensional, compressible, turbulent flow, steady-state analysis was performed using a Reynolds-averaged Navier–Stokes solver on each configuration to obtain the objective function values. Each configuration was analyzed at a freestream Mach number of 0.25 and at an angle of attack of 11 deg to mimic the takeoff conditions of a passenger aircraft. Multi-objective optimization was carried out using modeFRONTIER, using a radial basis function response surface approximation coupled with a genetic algorithm. Maximizing coefficients of the lift and lift-to-drag ratio and minimizing the coefficients of drag and the magnitude of the coefficient of the moment were the four simultaneous objectives. The Pareto-optimized multi-element winglet concept demonstrated superior performance at subsonic and transonic speeds.

Parametric reduced-order model approach for simulation and optimization of aeroelastic systems with structural nonlinearities

A method based on parametric reduced-order models to efficiently predict the transient response of aeroelastic systems with concentrated structural nonlinearities is presented. The approach approximates the nonlinear response in a piecewise-linear manner through time integration of sub-linear reduced-order models; these are parameterized with respect to the nonlinearity and are efficiently obtained by balanced truncation and interpolation. The procedure is applied to the optimization of a wing tip device for passive loads alleviation which features a nonlinear stiffness, showing the effectiveness and efficiency of the methodology.