Passive Wingtip Vortex Control by Using Tip-Mounted Half Delta Wings in Ground Effect

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Anan Lu ◽  
Tim Lee
Keyword(s):  
Vortex Flow ◽  
Ground Effect ◽  
Tip Vortex ◽  
Secondary Vortex ◽  
Flow Properties ◽  
Delta Wings ◽  
Vortex Control ◽  
Physical Mechanisms ◽  
Induced Drag ◽  
Wingtip Vortex

Abstract The ground effect on the wingtip vortex generated by a rectangular semiwing equipped with tip-mounted regular and reverse half delta wings was investigated experimentally. The passive tip vortex control always led to a reduced lift-induced drag as the ground was approached. In close ground proximity, the presence of the corotating ground vortex (GV) added vorticity to the tip vortex while the counter-rotating secondary vortex (SV) negated its vorticity level. The interaction of the GV and SV with the tip vortex and their impact on the lift-induced drag were discussed. Physical mechanisms responsible for the change in the vortex flow properties in ground effect were also provided.

Effect of Ground Boundary Condition on Near-Field Wingtip Vortex Flow and Lift-Induced Drag

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
A. Lu ◽  
T. Lee
Keyword(s):  
Boundary Condition ◽  
Near Field ◽  
Ground Effect ◽  
Tip Vortex ◽  
Secondary Vortex ◽  
Significant Discrepancy ◽  
Vortex Strength ◽  
Induced Drag ◽  
Wingtip Vortex ◽  
Ground Distance

Abstract The ground proximity is known to induce an outboard movement and suppression of the wingtip vortices, leading to a reduced lift-induced drag. Depending on the ground boundary condition, a large scatter exists in the published lift-induced drag and vortex trajectory. In this experiment, the ground boundary condition-produced disparity in the vortex strength and induced drag were evaluated. No significant discrepancy appeared for a ground distance or clearance larger than 30% chord. As the stationary ground was further approached, there was the appearance of a corotating ground vortex (GV), originated from the downstream progression of a spanwise ground vortex filament, which added vorticity to the tip vortex, leading to a stronger tip vortex and a larger lift-induced drag compared to the moving ground. For the moving ground, the ground vortex was absent. In close ground proximity, the rollup of the high-pressure fluid flow escaped from the wing's tip always caused the formation of a counter-rotating secondary vortex, which dramatically weakened the tip vortex strength and produced a large induced-drag reduction. The moving ground effect, however, induced a stronger secondary vortex, leading to a smaller lift-induced drag and a larger outboard movement of the tip vortex as compared to the stationary ground effect.

Experimental Study of Aerodynamics and Wingtip Vortex of a Rectangular Wing in Flat Ground Effect

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
A. Lu ◽  
V. Tremblay-Dionne ◽  
T. Lee
Keyword(s):  
Vortex Flow ◽  
Ground Surface ◽  
Ground Effect ◽  
Inviscid Flow ◽  
Tip Vortex ◽  
Vortex Strength ◽  
Induced Drag ◽  
Wingtip Vortex ◽  
Ground Distance ◽  
The Impact

The ground effect on the aerodynamics and tip vortex flow of a rectangular wing is investigated experimentally at Re = 2.71 × 105. The results show that there is a large lift increase with reducing ground distance. By contrast, only a small drag increase is observed in ground effect except in close ground proximity for which a great drag increase appears. The tip vortex also moves further outboard and upward with reducing ground distance. Near the ground, there is the presence of a corotating ground vortex (produced by the rolling up of the boundary layer developed on the ground surface), leading to an increased vortex strength. In extreme ground proximity, a counterrotating secondary vortex (SV) (induced by the crossflow of the tip vortex), relative to the tip vortex, appears which causes a reduced vortex strength and a lowered lift-induced drag, as well as a vortex rebound. The impact of ground effect on the vortex flow properties is also discussed. The lift-induced drag, computed based on the crossflow measurements via the Maskell wake integral method, in ground effect is also compared against the inviscid-flow predictions and wind tunnel total drag force measurements.

Wingtip Vortex Control Via Tip-Mounted Half-Delta Wings of Different Geometric Configurations

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
T. Lee ◽  
S. Choi
Keyword(s):  
Tip Vortex ◽  
Delta Wings ◽  
Vortex Control ◽  
Vortex Pattern ◽  
Geometric Configurations ◽  
Wingtip Vortex ◽  
Wing Chord ◽  
Naca 0012 ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The control of the tip vortex, generated by a rectangular NACA 0012 wing, via tip-mounted half-delta wings (HDWs), of different slendernesses Λ, root chords cr, and deflections δ, was investigated experimentally at Re = 2.45 × 105. The results show that regardless of Λ, cr, and δ, the addition of HDWs consistently led to a diffused tip vortex. The degree of diffusion was, however, found to increase with decreasing Λ and cr. HDWs with cr ≤ 50% of the baseline-wing chord c caused a rapid diffusion of vorticity and rendered a weak circulation flowlike tip vortex, suggesting an enhanced wake-vortex decay and alleviation. The cr = 0.5c HDW also produced an improved lift-to-drag ratio. A unique double-vortex pattern also exhibited downstream of the cr ≤ 50%c HDW wings. The interaction and merging of the double vortex were expedited by upward HDW deflection.

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

2017 ◽  
Vol 34 (2) ◽  
pp. 231-241
Author(s):  
M. Zhang ◽  
Y. K. Wang ◽  
S. Fu
Keyword(s):  
Reduction Method ◽  
Tip Vortex ◽  
Detached Eddy Simulation ◽  
Vortex System ◽  
Eddy Simulation ◽  
Induced Drag ◽  
Delayed Detached Eddy Simulation ◽  
Resistance Reduction ◽  
Wingtip Vortex ◽  
Formation And Evolution

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.

scholarly journals Induced Drag Savings From Ground Effect and Formation Flight in Brown Pelicans

1988 ◽  
Vol 135 (1) ◽  
pp. 431-444 ◽  
Author(s):  
F. REED HAINSWORTH
Keyword(s):  
Ground Effect ◽  
Formation Flight ◽  
Tip Vortex ◽  
Wing Beat ◽  
Vertical Variation ◽  
Induced Drag ◽  
Brown Pelicans ◽  
Vertical Displacements ◽  
Wing Tips ◽  
Wing Tip

Ciné films of brown pelicans flying in formation were used to measure altitudes and wing tip spacing (WTS, distance perpendicular to the flight path between wing tips of adjacent birds at maximum span) for birds flying in ground effect, and vertical displacements and WTS for birds flying out of ground effect. Views were near coplanar with the plane of flight paths, and maximum wing span was used for scale. Induced drag savings in ground effect averaged 49% for gliding. Average WTS varied considerably with no evidence for systematic positioning near an optimum. There were also no differences in average WTS between flapping and gliding in or out of ground effect. Vertical displacements out of ground effect varied less than WTS but more than vertical displacements in ground effect. Few birds had wing beat frequencies similar to the bird ahead as would be needed to track vertical variation in trailing wing tip vortex positions. Imprecision in WTS may be due to unpredictable flow fields in ground effect, and difficulty in maintaining position under windy conditions out of ground effect.

Wing tip vortex control using synthetic jets

2006 ◽  
Vol 110 (1112) ◽  
pp. 673-681 ◽  
Author(s):  
P. Margaris ◽  
I. Gursul
Keyword(s):  
Synthetic Jet ◽  
Synthetic Jets ◽  
Tip Vortex ◽  
Particle Image Velocimetry System ◽  
Driving Frequency ◽  
Velocity Measurements ◽  
Vortex Control ◽  
Image Velocimetry ◽  
Wing Tip ◽  
Jet Blowing

AbstractAn experimental investigation was conducted to study the effect of synthetic jet (oscillatory, zero net mass flow jet) blowing near the wing tip, as a means of diffusing the trailing vortex. Velocity measurements were taken, using a Particle Image Velocimetry system, around the tip and in the near wake of a rectangular wing, which was equipped with several blowing slots. The effect of the synthetic jet was compared to that of a continuous jet blowing from the same configurations. The results show that the use of synthetic jet blowing is generally beneficial in diffusing the trailing vortex and comparable to the use of continuous jet. The effect was more pronounced for the highest blowing coefficient used. The driving frequency of the jet did not generally prove to be a significant parameter. Finally, the instantaneous and the phase-locked velocity measurements helped explain the different mechanisms employed by the continuous and synthetic jets in diffusing the trailing vortex.

Experimental investigation on the structures and induced drag of wingtip vortices for different wingtip configurations

2020 ◽  
pp. 095441002094791
Author(s):  
Ze-Peng Cheng ◽  
Yang Xiang ◽  
Hong Liu
Keyword(s):  
Growth Rate ◽  
Form Factor ◽  
Drag Coefficient ◽  
Particle Image ◽  
Vortex Center ◽  
Streamwise Location ◽  
Induced Drag ◽  
Wingtip Vortex ◽  
Image Velocimetry ◽  
Drag And Lift

As an effective method to reduce induced drag and the risk of wake encounter, the winglet has been an essential device and developed into diverse configurations. However, the structures and induced drag, as well as wandering features of the wingtip vortices ( WTVs) generated by these diverse winglet configurations are not well understood. Thus, the WTVs generated by four typical wingtip configurations, namely the rectangular wing with blended/raked/split winglet and without winglet (Model BL/ RA/ SP/NO for short), are investigated in this paper using particle image velocimetry technology. Comparing with an isolated primary wingtip vortex generated by Model NO, multiple vortices are twisted coherently after installing the winglets. In addition, the circulation evolution of WTVs demonstrates that the circulation for Model SP is the largest, while Model RA is the smallest. By tracking the instantaneous vortex center, the vortex wandering behavior is observed. The growth rate of wandering amplitude along with the streamwise location from the quickest to the slowest corresponds to Model SP, Model NO, Model BL, Model RA in sequence, implying that the WTVs generated by model SP exhibit the quickest mitigation. Considering that the induced drag scales as the lift to power 2, the induced drag and lift are estimated based on the wake integration method, and then the form factor λ, defined by [Formula: see text], is calculated to evaluate the aerodynamic performance. Comparing with the result of Model NO, the form factor decreases by 7.99%, 4.80%, and 2.60% for Model RA, Model BL, Model SP, respectively. In sum, Model RA and BL have a smaller induced drag coefficient but decay slower; while Model SP has a larger induced drag coefficient but decays quicker. An important implication of these results is that reducing the strength of WTVs and increasing the growth rate of vortex wandering amplitude can be the mutual requirements for designing new winglets.

scholarly journals Numerical Investigation of Tip-Vortex Cavitation Noise of an Elliptic Wing Using Coupled Eulerian-Lagrangian Approaches

2020 ◽  
Vol 10 (17) ◽  
pp. 5897 ◽  
Author(s):  
Garam Ku ◽  
Cheolung Cheong ◽  
Hanshin Seol
Keyword(s):  
Flow Field ◽  
Numerical Method ◽  
Vortex Flow ◽  
Acoustic Pressure ◽  
Tip Vortex ◽  
Experimental Result ◽  
Cavitation Noise ◽  
Navier Stokes Equation ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception

In this study, a numerical methodology is developed to investigate the tip-vortex cavitation of NACA16-020 wings and their flow noise. The numerical method consists of a sequential one-way coupled application of Eulerian and Lagrangian approaches. First, the Eulerian method based on Reynolds-averaged Navier–Stokes equation is applied to predict the single-phase flow field around the wing, with particular emphasis on capturing high-resolution tip-vortex flow structures. Subsequently, the tip-vortex flow field is regenerated by applying the Scully vortex model. Secondly, the Lagrangian approach is applied to predict the tip-vortex cavitation inception and noise of the wing. The initial nuclei are distributed upstream of the wing. The subsequent time-varying size and position of each nucleus are traced by solving spherically symmetric bubble dynamics equations for the nuclei in combination with the flow field predicted from the Eulerian approach. The acoustic pressure at the observer position is computed by modelling each bubble as a point source. The numerical results of the acoustic pressure spectrum are best matched to the measured results when the nuclei number density of freshwater is used. Finally, the current numerical method is applied to the flows of various cavitation numbers. The results reveal that the cavitation inception determined by the predicted acoustic pressure spectrum well matched the experimental result.

Numerical Experiments for Flow Around a Ducted Tip Hydrofoil

2002 ◽  
Author(s):  
Hildur Ingvarsdo´ttir ◽  
Carl Ollivier-Gooch ◽  
Sheldon I. Green
Keyword(s):  
Turbulence Model ◽  
Vortex Core ◽  
Vortex Flow ◽  
Computational Study ◽  
Near Field ◽  
Vortex Formation ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Computational Studies ◽  
Tip Vortices

The performance and cavitation characteristics of marine propellers and hydrofoils are strongly affected by tip vortex behavior. A number of previous computational studies have been done on tip vortices, both in aerodynamic and marine applications. The focus, however, has primarily been on validating methods for prediction and advancing the understanding of tip-vortex formation in general, rather than showing effects of tip modifications on tip vortices. Studies of the most relevance to the current work include computational studies by Dacles-Mariani et al. (1995) and Hsiao and Pauley (1998, 1999). Daeles-Mariani et al. carried out interactively a computational and experimental study of the wingtip vortex in the near field using a full Navier-Stokes simulation, accompanied with the Baldwin-Barth turbulence model. Although they showed improvement over numerical results obtained by previous researchers, the tip vortex strength was underpredicted. Hsiao and Pauley (1998) studied the steady-state tip vortex flow over a finite-span hydrofoil, also using the Baldwin-Barth turbulence model. They were able to achieve good agreement in pressure distribution and oil flow pattern with experimental data and accurately predict vertical and axial velocities of the tip vortex core within the near-field region. Far downstream, however, the computed flow field was overly diffused within the tip vortex core. Hsiao and Pauley (1999) also carried out a computational study of the tip vortex flow generated by a marine propeller. The general characteristics of the flow were well predicted but the vortex core was again overly diffused.

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