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Winglet is a wingtip device that was developed to improve aircraft flight performance by reducing induced drag. The induced drag produced by the NXXX aircraft is considered too excessive because the simple wingtip currently available is still not optimal in reducing induced drag, so a new more optimal wingtip is needed. This research aims to analyze the influence of blended winglet parameters on the aerodynamic characteristics of the NXXX aircraft such as CL and CD. Not only that, pitch moment coefficient (CM) is also studied to determine how trim drag can increase with the consequent increase of aerodynamic efficiency (CL/ CD) which currently has not been specifically researched yet. Winglet parameters in this study include variations in taper ratio, winglet height, cant angle, trailing edge sweep, and blending radius that there is not enough analysis about it now. Computational Fluid Dynamics (CFD) simulation uses Ansys CFX with the Shear Stress Transport (SST) turbulence model is used to obtain wing aerodynamic data. This research concludes that the best winglet configuration is taper ratio of 0.2, blending radius of 15 %, winglet height of 30 %, cant angle of 15°, and trailing edge sweep of −0.6°. Apart from that, it was also found that all winglet configurations increased CL, CLmax, and also lift slope (a). Almost all winglets also reduce the critical angle of attack, reduce CD, and increase CM. This simulation finds that addition of blended winglet can increase aerodynamic efficiency up to 17.51 % in cruise condition using the variation of winglet height.

This study presents the empirical comparison between the wing root and wingtip corrugation patterns of dragonfly wing in the newly-built wind-tunnel at the IAUN. The main objective of the research is to investigate the effect of wingtip and wing root corrugations on aerodynamic forces and the flow physics around the cross-sections at Re=10000 and the angle of attack of 0° to 30°. For this aim, two cross-sections are extracted from wing root (first cross-section) and wingtip (second cross-section). The first cross-section has corrugations with higher density than the second cross-section. The comparison of lift coefficients obtained from pressure distribution and force measurement indicates an acceptable agreement between the results. Also, Particle Image Velocity (PIV) technique is used to measure the velocity field. The results show that all corrugation patterns do not have positive effects on the aerodynamic forces. The second cross-section can generate considerable aerodynamic forces compared to the first cross-section. At a=25°, the lift coefficient generated by the second cross-section is 90% and 25% higher than that of the first cross-section and the flat plate, respectively. Based on results, corrugations in the wing root's vicinity have a crucial role in the solidity of insect wings; however, corrugations in the wing tip's vicinity play a vital role in generating adequate aerodynamic forces. The comparison conducted in the current research reveals the second cross-section is an appropriate replacement for the flat plate in MAVs due to generating more essential forces for flight. [ABSTRACT FROM AUTHOR]

A low-amplitude high-frequency flow control strategy for mitigation of transient tip stall is demonstrated for the case of a finite swept wing using high-fidelity wall-resolved large-eddy simulations. A wing of aspect ratio =4 and NACA 0012 section is considered at freestream Mach number M∞=0.1 and chord Reynolds number Rec=2×105. The wing undergoes an oscillatory pitching motion with reduced frequency k=π/16 and angle of attack between α=4 and 22 deg, resulting in deep dynamic tip stall for the uncontrolled case. Spanwise uniform low-amplitude pulsed forcing is imparted through a zero-net mass flow blowing/suction slot located on the wing lower surface near the leading edge using both moderate and high frequencies, Stf=fc/U∞=5 and 50, respectively. The imposed small fluctuations are amplified through the natural receptivity of the laminar separation bubble (LSB) and, in the case of the highest frequency, completely inhibit its bursting along the wing, which precludes outboard flow separation and subsequent dynamic tip stall. The lower-frequency forcing cannot overcome eventual bursting of the LSB near the wingtip; however, the resulting separation is localized to the tip region unlike the full outboard unloading of the uncontrolled case. Conditioning of the leading-edge flow through targeted manipulation of the LSB and its inherent dynamics maintained or enhanced the effectively attached flow throughout the pitching cycle, resulting in significant reductions in the cycle-averaged drag and in the force and moment excursions. [ABSTRACT FROM AUTHOR]

We present a medium-fidelity aeroelastic framework for computing intermittently separating three-dimensional (3-D) flows around high-aspect ratio wings with a significantly reduced computational cost compared to the computational-fluid- dynamics-based method. To achieve that, we propose a modified three-dimensional vortex panel method with leading-edge separation controlled by leading-edge suction parameter theory, and its incorporation in a coupled aeroelastic solver for the dynamic response of these systems. Numerical verifications and simulations are presented on both attached and separated aeroelastic test cases, demonstrating the method on postflutter limit-cycle oscillation of a cantilever wing, and leading-edge separation on a deploying wing, a complex kinematic response. In both cases we were able to capture three-dimensional interactions on intermittently separating dynamic flowfields using a low computational cost. [ABSTRACT FROM AUTHOR]

The effects of wake crossing at any horizontal angle, airspeed, and altitude are considered, focusing on crossing at cruise speeds at altitudes close to the tropopause. The roll effect is considered in two cases: 1) specification of the aileron deflection as a function of time that exactly compensates for the rolling moment induced on the crossing aircraft by the wake of the leading aircraft so that the crossing aircraft is undisturbed; and 2) in the case when the available roll control power is not sufficient to compensate completely for the wake induced rolling moment, the resulting roll rate and bank angle of the crossing aircraft are calculated as a function of time. The distinction between the two cases is made by a safe separating distance or safe separating time: beyond which, roll compensation 1) is possible; and below which, rolling motion 2) is unavoidable. Besides the roll acceleration, roll rate, and bank angle for the roll axis, the effects of wake crossing are also considered for the vertical axis, including the load factor, vertical velocity, and altitude change. The theory applies to any pair of aircraft and indicates the dependence on aircraft parameters, flight, and atmospheric conditions. [ABSTRACT FROM AUTHOR]

This work presents the effect of wingtip-mounted propellers on the aircraft drag polar, identified from in-flight measurements. In previous wind-tunnel experiments, significant reductions in drag and an increase in propulsive efficiency through interaction between induced flow by the wingtip-mounted propellers and the flowfield of the wing itself have been claimed. So far, however, these effects have never been verified in actual flight. That gap is closed here by presenting the results of in-flight measurements. A 33.3% scaled version of the manned, electric e-Genius aircraft has been fitted with a wingtip propulsion system and an elaborate measurement system, which allows quantifying the aforementioned effects. The drag polar is deduced through weighted least-squares parameter estimation for different settings and configurations of the wingtip propellers. The findings are compared to results from previous wind-tunnel experiments. The paper further discusses secondary effects that were observed during the flight tests and their influence on the general potential of wingtip propulsion. [ABSTRACT FROM AUTHOR]

In this paper, the low-speed aerodynamic characteristics of a basic wing-fuselage supersonic biplane incorporating trailing-edge flaps are assessed using both wake and balance measurements. The effects of the flap attachment location, flap deflection, and flap length are evaluated. These experiments employed a flow velocity of 20 m/s and a Reynolds number of 1.4×105, along with a model having a simple three-dimensional wing-fuselage supersonic biplane configuration; and wake data were obtained with a five-hole probe. Installing the flap near the wingtip was found to produce strong interactions between the wingtip and the flap vortices in the wake, leading to significant induced drag at the wingtip. The local lift increases not only at the flap attachment location but also over the entire wingspan. Positioning the flaps near the body is determined to be more effective, and it gives rise to higher lift and smaller drag than in the case of installing the flap near the wingtip, due to the effects of the tapered wing configuration. The effects of the flap length and flap deflection are also confirmed, with longer flaps and larger flap deflection giving higher lift and more drag. [ABSTRACT FROM AUTHOR]

The recent growing interest in urban air mobility (UAM) worldwide has led to the demand for physical analyses of the aerodynamic performance and aeroacoustic characteristics of electric vertical takeoff and landing (eVTOL) rotorcraft. In a UAM eVTOL rotorcraft, the smaller vortices generated from multiple propulsors interact with lifting surfaces such as wings, fuselage, and propellers in a complex manner. Therefore, to accurately predict the performance and noise of UAM eVTOL rotorcraft, vortices should be preserved with little dissipation; and their interactions must be modeled precisely. These requirements need a numerical algorithm with a refined resolution than that allowed by conventional schemes. This paper proposes a newly modified enhanced multidimensional limiting process (eMLP) for vorticity conservation (eMLP-VC), which improves the original eMLP by accounting for the fact that most rotorcraft flowfields are vortex dominated and subsonic. For advanced capability in preserving vortices, the distinguishing criterion was modified through vortex profile analysis, and low-Mach-number adjustment was performed by reconstructing the interpolated primitive variables. The proposed scheme was applied to wave propagation, shock discontinuity, double Mach reflection, propeller-wing interaction, and Second Higher-Harmonic Control Aeroacoustic Rotor Test problems. The computed results confirmed that eMLP-VC exhibits superior resolution, numerical stability, and computational time efficiency as compared to the multidimensional limiting process, eMLP, and weighted essentially nonoscillatory methods. [ABSTRACT FROM AUTHOR]

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The present research focuses on the experimental investigation of the effectiveness of synthetic jet actuation on a pair of counter-rotating vortices generated by an unswept, low aspect ratio, squared-tipped wing in order to preserve the mutual induction during their evolution. The synthetic jet is actuated at Crow and Widnall's instability frequencies (F + = 0.071 , 0.55) and at a fixed momentum coefficient C μ = 0.2 % with the goal of reducing the vortex strength and the induced circumferential velocity. The effect of the jet exit section area, and thus the characteristic jet velocity, has been investigated by testing three wing models equipped with a synthetic jet issuing through a rectangular slot of constant length and three different values of the height, equal to 0.01, 0.02, and 0.04 chord lengths, respectively. A phase-locked stereoscopic particle image velocimetry setup has been designed and implemented to carry out a parametric study in the near wake of the wing models at four downstream distances from the wing trailing edge, namely equal to 0.1, 0.5, 1 and 2 chord lengths. The slot with a height to chord ratio of 4%, yields the minimum vorticity level, the maximum vortex diffusion with a diameter up to 3 times greater than the baseline reference value, and lower values of the vortex circulation. This effect, together with the periodic motion along a ± 45 ∘ direction experienced by the vortex after the synthetic jet blowing, is beneficial in terms of an anticipated instability of the tip vortices as well as of the mitigation of the blade-vortex-interaction in propellers. [ABSTRACT FROM AUTHOR]

The present contribution is a companion paper of [9] which presents a preliminary design of the flight control system of a Light Sport Aircraft (based on previous wind tunnel analysis), validation process, aerodynamic simulations in ANSYS CFX and multibody dynamics in Adams. The main purpose of this study is to obtain knowledge on simulation software’s, as Ansys and Adams, in order to design, calculate and improve the flight control mechanism of an ultralight aircraft.

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Wingtip vortices have been proven to be detrimental to both aircraft efficiency and safety due to their adverse effects such as wake hazard, blade vortex interaction noise and induced drag. Despite the extensive literature on the subject, the number of experimental works featuring far field velocity measurements under active control is very limited. The present work deals with the experimental investigation of the effectiveness of synthetic jet actuation on the control of wingtip vortices and their wake hazard. In order to preserve the mutual induction of the counter-rotating vortices during their evolution, an unswept, low aspect ratio, squared-tipped, finite-span wing is employed. The synthetic jet actuation is based on triggering the inherent instabilities of Crow and Widnall at different values of the momentum coefficient C μ with the goal of reducing the vortex strength and obtaining an anticipated vortex break up. Different exit geometries of the synthetic jets have been tested to analyze the effects of the jet velocity and position on the wingtip vortices. Phase-locked measurements of the velocity field in the far wake at a distance from the wing trailing edge from 26 to 80 chord lengths have been performed via stereoscopic particle image velocimetry. The effects of blowing at high momentum coefficient C μ = 1 % are demonstrated to be remarkable on the mitigation of the wingtip vortices. On the other hand, both the time and phase-averaged results suggest that, at relatively low values of C μ (0.2%), using a larger synthetic jet exit section area allows to greatly affect the wingtip vortices' features causing a striking alleviation of the vorticity distribution up to 90% with respect to the baseline reference case. In fact, due to the actuation at low frequency, the vortex instability is prematurely risen up and amplified, leading to early vortices linking and their consequent dissipation. [ABSTRACT FROM AUTHOR]

Renewable energy has become the leading resource as eco-friendly energy. The recent research on wind energy explores the opportunity of increasing the effectiveness of horizontal axis wind turbine and also reduction of lift-induced drag by adding winglets at the tip of the turbine blade. This paper describes the influence of different model winglets attached to wind mill turbine blade. The performance of winglets attached blades in wind turbine was investigated in ANSYS CFD to evaluate the power variation on low speed wind mill. This virtual investigation was conducted for three different winglets individually. The virtual analysis showed that the blended winglet was the best winglet compared to the other two turbine blades design. The numerical investigation revealed that adding a blended winglet to the base line turbine blade increased the output power by 4 watts resulting in overall increase in power by 2% to 3% output and power coefficient. [ABSTRACT FROM AUTHOR]

Studying wing downwash, which is caused by the wingtip effect, and its influence on horizontal tail is important for aircraft design. In this work, wing downwash was investigated using experimental and numerical methods. Sets of main wings and horizontal tails were fixed in a tunnel test chamber. For determining the wingtip effect and the wing downwash affecting the horizontal tail, experiments were performed, in which the pressure distributions near the main wingtip and on the upper and lower surfaces of the tail were measured. These experimental models were used in numerical calculations by the solving of differential equations for viscous flows and use of a singularity method for potential flows. The singularity method can be applied to determine the wing lift, as indicated by comparisons between the experimental and numerical results of the pressure distribution on the wing. Moreover, the wingtip and wing downwash effects influencing the horizontal tail should be determined with use of experimental and numerical methods that solve differential equations of viscous flow. In addition to the results regarding the pressure distributions near the main wing and on the horizontal tail, the longitudinal velocity, downwash velocity, and downwash angle distributions in the main wing wake were analyzed. We also investigated the kinetic parameters of the flow in mixed zones between the main wing downwash and the tail upwash. [ABSTRACT FROM AUTHOR]

Abstract Winglets can reduce effect of wingtip vortices on the wind turbine performance can be reduced by diffusing the vortices from the blade tips. Unlike non-rotating wings, winglets have not been widely investigated for moving blades of wind turbines, while there is a potential they could enable the wind turbine rotor to capture more kinetic energy from wind. There have been a number of studies on the effect of winglet parameters and configurations on the wind turbine performance, however a combined effect of winglet planform and airfoil has not been investigated in details. The present work reports on the study of the effect of winglet planform and winglet airfoil on the wind turbine performance using Computational Fluid Dynamics (CFD). The National Renewable Energy Laboratory (NREL) phase VI rotor with 10 m diameter was used as the baseline and the CFD results were validated with the available experimental data on the output power and pressure coefficients. Different designs of winglet with different heights, cant angles, planforms and airfoils have been numerically tested and optimised. The best improvement in the performance is achieved when a 15 cm rectangular winglet with the S809 airfoil and 45° cant angle is used. Highlights • Effect of winglet planform and airfoil on wind turbine performance are studied. • An optimum winglet design has been found for the wind turbine blade in this paper. • The output power of wind turbine is increased using the optimum winglet design. • Extended blade can increase the thrust force. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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In this study numerical calculations are conducted to understand implementation of different wingtip device for wingtip vortexes formation. Numerical methods are performed over NACA 0012 winglet at the varying Reynolds numbers from 0.5x106 to 1x106 with the angle of attack 10° and compared with other study. Implementations of winglet are divided into four categories and these are one winglet up or down sloping, split winglet up and down sloping, and single winglet with two-step inclined. First, up and down sloping winglet are designed and simulated then split winglet are investigated numerically with the varying angle. Finally, winglets with two step inclined angles are investigated. For the up sloping winglet, wingtip vortexes formation is reduced considerably as the angle with wing surface approaches 90 degrees. But vortexes formation is clearly happening at the angle starting less than 90° and beyond 135 degree. For the down sloping, while there is a visible vortex formation below 90 degrees but more uniform flow is observed compared to conventional wing tips at around 90 degrees. For the split winglet configurations, less vortex formation is observed generally compared to other. As a result, single or split winglet up or down sloping perpendicular or wider angle with lateral surface decreases wingtip vortex formations. [ABSTRACT FROM AUTHOR]

The present contribution is a companion paper of [9] which presents a preliminary design of the flight control system of a Light Sport Aircraft (based on previous wind tunnel analysis), validation process, aerodynamic simulations in ANSYS CFX and multibody dynamics in Adams. The main purpose of this study is to obtain knowledge on simulation software's, as Ansys and Adams, in order to design, calculate and improve the flight control mechanism of an ultralight aircraft. [ABSTRACT FROM AUTHOR]

The aerodynamic optimization of horizontal axis wind turbine has became one of the most important challenge in the renewable energy field. Over the past few years, many researchers have drawn more attention to the physical processes of the wind energy conversion and precisely the identification of the main causes of energy losses. This paper presents an experimental investigation of near wake dynamics for a model horizontal axis wind turbine in a wind tunnel. The coherent structures downstream of the rotor were studied for different tip speed ratios using the Particle Image Velocimetry (PIV) technique. The influence of the tip vortex meandering was discussed and analyzed using the Proper Orthogonal Decomposition (POD) method. The high-energy modes show that radial meandering is the most energetic source of perturbation in each tip vortex sub-region. The energy fraction of these modes increase gradually during the development of the helical tip vortex filament, which confirm the growth of vortex wandering amplitude in the near wake. [ABSTRACT FROM AUTHOR]

The paper presents high-speed stereo particle image velocimetry investigation of the NASA Common Research Model wing tip vortex. A three-percent scaled semi-span model, without nacelle and pylon, was tested in the 32- by 48-inch Indraft tunnel, at the Fluid Mechanics Laboratory at the NASA Ames Research Center. Turbulence investigation of the wing tip vortex is presented. Measurements of the wing-tip vortex were performed in a vertical cross-stream plane three tip-chords downstream of the wing tip trailing edge with a 2 kHz sampling rate. Experimental data are analyzed in the invariant anisotropy maps for three various angles of attack (0°, 2°, and 4°) and the same speed generated in the tunnel (V∞ = 50 m/s). This corresponds to a chord Reynolds number 2.68·105, where the chord length of 3" is considered the characteristic length. The region of interest was x = 220 mm and y = 90 mm. The 20 000 particle image velocimetry samples were acquired at each condition. Velocity fields and turbulence statistics are given for all cases, as well as turbulence structure in the light of the invariant theory. Prediction of the wing tip vortices is still a challenge for the computational fluid dynamics codes due to significant pressure and velocity gradients. [ABSTRACT FROM AUTHOR]

Prediction of the characteristics of turbulent flow with streamline curvature is of great importance in engineering applications. In this paper, a curvature-corrected filterbased turbulent model is suggested by applying the Spalart-Shur correction term. This new version of the model (FBMCC) has been tested and verified through two canonical benchmarks with strong streamline curvature: the flow in a two-dimensional U-duct and the free shear flow past NACA0012 airfoil with a round tip. Predictions of the FBMCC model are compared with available experimental data and the corresponding results of the original FBMmodel. The numerical results show that the FBM-CC model significantly improves the sensitivity to the effect of streamline curvature and the numerical calculation accuracy, in relatively good agreement with the experimental data, which suggests that this proposed model may be employed to simulate the turbulent curved flow in engineering applications. [ABSTRACT FROM AUTHOR]

The attenuation of wingtip/blade vortices has been one of the primary concerns in aviation safety and blade-vortex noise. In an effort to effectively dissipate the vortex intensity, a trailing-edge (TE) chipped wing concept was suggested. In this study, to exploit the potential of the chipped wingtip concept for alleviating the tip vortex, a series of numerical simulations are conducted. The numerical simulations are performed using open source code, OpenFOAM. The wake structures are measured for different wingtip shapes. The chip depth and location are varied to evaluate the vortex alleviation rate and aerodynamic characteristics. As a result of numerical simulation, it is confirmed that the vortex dissipation rate of the tip-chipped wing is higher than that of a TE-chipped wing. For the tip-chipped wing, the counter-rotating vortex is found to be strong enough to weaken the primary vortex. The dissipation rate increases as the location of the chip gets closer to the leading-edge, and as the depth of the chip increases. A trade-off relationship between vortex alleviation and an increase in drag is confirmed. For example, the MID D3 attenuates the strength of the wingtip vortex by 51%, while the drag is increased within 5%. [ABSTRACT FROM AUTHOR]

Wake surveys of 2 swept NACA 0021 wings were conducted at angles of attack of 0°, 3°, 6°, 9°, and 12°. One wing had a smooth leading edge and the other had a tubercled leading edge. Sweeping the tubercled wing resulted in one vortex in each vortex pair being at least 4 times stronger than the other. There was little difference between the strength of the wingtip vortices of either wing at 3°. From 6° onwards tubercles reduced the strength of the wingtip vortex. The tubercle troughs tended to produce local maxima and minima in the profile and induced drag coefficients, respectively. The converse was true over the peaks. The change in the profile, induced, and total drag coefficients primarily arose from over the wingspan; there was little contribution from the wingtip region. [ABSTRACT FROM AUTHOR]