Trailing edge flap influence on leading edge vortex flap aerodynamics

Experimental and numerical studies have been performed to investigate the effects of the leakage flow tangential velocity on the secondary flow and aerodynamic loss in an axial compressor cascade with a labyrinth seal. Six selected leakage flow tangential (vy/Uhub = 0.15, 0.25, 0.35, 0.45, 0.55 and 0.65) have been tested. In addition to the classical “secondary” flow, shroud trailing edge vortex and shroud leading edge vortex are examined. The overall loss decreases with increasing leakage flow tangential velocity. Increased leakage flow tangential velocity underturns the hub endwall flows through the blade passage, weakening the suction side hub corner separation. Due to the suction effect of the downstream cavity, increasing leakage flow tangential velocity weakens the shroud trailing edge vortex. Also, increasing leakage flow tangential velocity strengthens the shroud leading edge vortex, weakening the pressure side leg of the horseshoe vortex, and, in turn, the passage vortex. Thus, the overall loss is reduced with increasing leakage flow tangential velocity.

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The leading-edge vortex of swift wing-shaped delta wings

Royal Society Open Science ◽

10.1098/rsos.170077 ◽

2017 ◽

Vol 4 (8) ◽

pp. 170077 ◽

Cited By ~ 7

Author(s):

Rowan Eveline Muir ◽

Abel Arredondo-Galeana ◽

Ignazio Maria Viola

Keyword(s):

Reynolds Number ◽

Delta Wing ◽

Leading Edge ◽

Trailing Edge ◽

Delta Wings ◽

Leading Edge Vortex ◽

Wing Model ◽

Image Velocimetry ◽

Edge Vortex ◽

First Time

Recent investigations on the aerodynamics of natural fliers have illuminated the significance of the leading-edge vortex (LEV) for lift generation in a variety of flight conditions. A well-documented example of an LEV is that generated by aircraft with highly swept, delta-shaped wings. While the wing aerodynamics of a manoeuvring aircraft, a bird gliding and a bird in flapping flight vary significantly, it is believed that this existing knowledge can serve to add understanding to the complex aerodynamics of natural fliers. In this investigation, a model non-slender delta-shaped wing with a sharp leading edge is tested at low Reynolds number, along with a delta wing of the same design, but with a modified trailing edge inspired by the wing of a common swift Apus apus . The effect of the tapering swift wing on LEV development and stability is compared with the flow structure over the unmodified delta wing model through particle image velocimetry. For the first time, a leading-edge vortex system consisting of a dual or triple LEV is recorded on a swift wing-shaped delta wing, where such a system is found across all tested conditions. It is shown that the spanwise location of LEV breakdown is governed by the local chord rather than Reynolds number or angle of attack. These findings suggest that the trailing-edge geometry of the swift wing alone does not prevent the common swift from generating an LEV system comparable with that of a delta-shaped wing.

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Three-dimensional effects in hovering flapping flight

Journal of Fluid Mechanics ◽

10.1017/jfm.2012.163 ◽

2012 ◽

Vol 702 ◽

pp. 102-125 ◽

Cited By ~ 53

Author(s):

T. Jardin ◽

A. Farcy ◽

L. David

Keyword(s):

Three Dimensional ◽

Leading Edge ◽

Flapping Flight ◽

Length Scale ◽

Two Dimensional ◽

Trailing Edge ◽

Leading Edge Vortex ◽

Dimensional Flow ◽

Dimensional Effects ◽

Edge Vortex

AbstractThis paper aims at understanding the influence of three-dimensional effects in hovering flapping flight. Numerical simulations at a Reynolds number of 1000 are performed to compare two types of flapping kinematics whose plunging phase is characterized by either a rectilinear translation or a revolving motion. In this way, we are able to isolate the three-dimensional effects induced by the free end condition from that induced by the spanwise incident velocity gradient (and the associated implicit Coriolis and centrifugal effects). In the rectilinear translation case, the analysis of the wake and of the aerodynamic loads reveals that the wingspan can be compartmented into three distinct regions whether it is predominantly subjected to an unstable two-dimensional flow, a stable three-dimensional flow or both two-dimensional and three-dimensional effects. It is found that this partitioning exhibits common features for three different aspect ratios of the wing. In conjunction with the previous results of Ringuette, Milano & Gharib (J. Fluid Mech., vol. 581, 2007, pp. 453–468), this suggests that the influence of the tip vortex over the wingspan is driven by a characteristic length scale. In addition, this length scale matches the position of the connecting point between leading and tip vortices observed in the revolving case, providing insight into the connecting process. In both translating and revolving cases, leading edge vortex attachment and strong spanwise velocities are found to be strongly correlated phenomena. Spanwise velocities (that mostly confine at the periphery of the vortices), together with downward velocities, do not only affect the leading edge vortex but also act as an inhibitor for the trailing edge vortex growth. As a consequence, cross-wake interactions between leading and trailing edge vortices are locally limited, hence contributing to flow stabilization.

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Control of leading-edge vortex breakdown by trailing edge injection

10.2514/6.1999-3202 ◽

1999 ◽

Cited By ~ 2

Author(s):

Anthony Mitchell ◽

Pascal Molton ◽

Didier Barberis ◽

Jean Delery

Keyword(s):

Vortex Breakdown ◽

Leading Edge ◽

Trailing Edge ◽

Leading Edge Vortex ◽

Edge Vortex

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UNSTEADY AERODYNAMIC PERFORMANCE OF MODEL WINGS AT LOW REYNOLDS NUMBERS

Journal of Experimental Biology ◽

10.1242/jeb.174.1.45 ◽

1993 ◽

Vol 174 (1) ◽

pp. 45-64 ◽

Cited By ~ 33

Author(s):

M. H. Dickinson ◽

K. G. Gotz

Keyword(s):

Insect Flight ◽

Delta Wing ◽

Force Production ◽

Leading Edge ◽

Reynolds Numbers ◽

Aerodynamic Forces ◽

Trailing Edge ◽

Leading Edge Vortex ◽

Precise Knowledge ◽

Edge Vortex

The synthesis of a comprehensive theory of force production in insect flight is hindered in part by the lack of precise knowledge of unsteady forces produced by wings. Data are especially sparse in the intermediate Reynolds number regime (10<Re<1000) appropriate for the flight of small insects. This paper attempts to fill this deficit by quantifying the time-dependence of aerodynamic forces for a simple yet important motion, rapid acceleration from rest to a constant velocity at a fixed angle of attack. The study couples the measurement of lift and drag on a two-dimensional model with simultaneous flow visualization. The results of these experiments are summarized below. 1. At angles of attack below 13.5°, there was virtually no evidence of a delay in the generation of lift, in contrast to similar studies made at higher Reynolds numbers. 2. At angles of attack above 13.5°, impulsive movement resulted in the production of a leading edge vortex that stayed attached to the wing for the first 2 chord lengths of travel, resulting in an 80 % increase in lift compared to the performance measured 5 chord lengths later. It is argued that this increase is due to the process of detached vortex lift, analogous to the method of force production in delta-wing aircraft. 3. As the initial leading edge vortex is shed from the wing, a second vortex of opposite vorticity develops from the trailing edge of the wing, correlating with a decrease in lift production. This pattern of alternating leading and trailing edge vortices generates a von Karman street, which is stable for at least 7.5 chord lengths of travel. 4. Throughout the first 7.5 chords of travel the model wing exhibits a broad lift plateau at angles of attack up to 54°, which is not significantly altered by the addition of wing camber or surface projections. 5. Taken together, these results indicate how the unsteady process of vortex generation at large angles of attack might contribute to the production of aerodynamic forces in insect flight. Because the fly wing typically moves only 2–4 chord lengths each half-stroke, the complex dynamic behavior of impulsively started wing profiles is more appropriate for models of insect flight than are steady-state approximations.

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Size effect in insect flight: leading-edge vortex, trailing-edge vortex and tip vortex

Journal of Biomechanics ◽

10.1016/s0021-9290(06)84425-8 ◽

2006 ◽

Vol 39 ◽

pp. S356-S357 ◽

Cited By ~ 3

Author(s):

H. Liu ◽

H. Aono ◽

Y. Inada ◽

W. Shyy

Keyword(s):

Size Effect ◽

Insect Flight ◽

Leading Edge ◽

Tip Vortex ◽

Trailing Edge ◽

Leading Edge Vortex ◽

Edge Vortex

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Characterization of Vortex Dynamics in the Near Wake of an Oscillating Flexible Foil

Volume 1B, Symposia: Fluid Mechanics (Fundamental Issues and Perspectives; Industrial and Environmental Applications); Multiphase Flow and Systems (Multiscale Methods; Noninvasive Measurements; Numerical Methods; Heat Transfer; Performance); Transport Phenomena (Clean Energy; Mixing; Manufacturing and Materials Processing); Turbulent Flows — Issues and Perspectives; Algorithms and Applications for High Performance CFD Computation; Fluid Power; Fluid Dynamics of Wind Energy; Marine Hydrodynamics ◽

10.1115/fedsm2016-7806 ◽

2016 ◽

Author(s):

Firas F. Siala ◽

Alexander D. Totpal ◽

James A. Liburdy

Keyword(s):

Large Scale ◽

Flow Characteristics ◽

Leading Edge ◽

Mean Flow ◽

Near Wake ◽

Trailing Edge ◽

Mean Velocity ◽

Leading Edge Vortex ◽

Edge Vortex ◽

The Mean

An experimental study was conducted to explore the effect of surface flexibility at the leading and trailing edges on the near-wake flow dynamics of a sinusoidal heaving foil. Mid-span particle image velocimetry measurements were taken in a closed loop wind tunnel at a Reynolds number of 25,000 and at a range of reduced frequencies (k = fc/U) from 0.09–0.20. Time resolved and phase locked measurements were used to describe the mean flow characteristics and phase averaged vortex structures and their evolution throughout the oscillation cycle. Large eddy scale decomposition and swirl strength analysis were used to quantify the effect of flexibility on the vortical structures. The results demonstrate that flexibility at the trailing edge has a minimal influence on the mean flow characteristics when compared to the purely rigid foil. The mean velocity deficit for the flexible trailing edge and rigid foils is shown to remain constant for all reduced frequencies tested. However, the trailing edge flexibility increases the swirl strength of the small scale structures, which results in enhanced cross stream dispersion of the mean velocity profile. Flexibility at the leading edge is shown to generate a large scale leading edge vortex for k ≥ 0.18. This results in a reduction in the swirl strength due to the complex vortex interactions when compared to the flexible trailing edge and rigid foils. Furthermore, it is shown that the large scale leading edge vortex is responsible for extracting a significant portion of the energy from the mean flow, resulting in a substantial reduction of mean flow momentum in the wake. The kinetic energy loss in the wake is shown to scale well with the energy content of the leading edge vortex.

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