Characteristic length scales for vortex detachment on plunging profiles with varying leading-edge geometry

Rival, David E.; Kriegseis, Jochen; Schaub, Pascal; Widmann, Alexander; Tropea, Cameron

doi:10.1007/s00348-013-1660-x

Cited by 98 publications

(75 citation statements)

References 18 publications

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“…7. Detachment of the LEV also takes place at the root first as the critical vortex size of one chord length suggested by Rival et al (2014) is reached earlier than at the tip of the wing.…”

Section: Discussionmentioning

confidence: 98%

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Investigation of vortex development on accelerating spanwise-flexible wings

Jain

Wong

Rival

2015

Journal of Fluids and Structures

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“…7. Detachment of the LEV also takes place at the root first as the critical vortex size of one chord length suggested by Rival et al (2014) is reached earlier than at the tip of the wing.…”

Section: Discussionmentioning

confidence: 98%

“…Recently, Rival et al (2014) found that the stable attachment of the LEV is determined by its size in relation to the wing's chord length. As the LEV grows, the rear stagnation point moves along the chord until it reaches the trailing edge, at which point the LEV separates and detaches from the wing.…”

Section: Introductionmentioning

confidence: 99%

Investigation of vortex development on accelerating spanwise-flexible wings

Jain

Wong

Rival

2015

Journal of Fluids and Structures

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“…A hypothetical balance of vorticity is shown in figure 1, where spanwise-oriented vorticity entering the LEV from the leading-edge shear layer is balanced by a spanwise convection of vorticity. It has been shown by Rival et al (2014) that LEV attachment is only topologically compatible with vortices smaller than one chord length c in scale. The vorticity generated in the leading-edge shear layer of a rotating profile must therefore be balanced by either the transport or annihilation of vorticity in order to limit vortex growth as a necessary condition for LEV stability.…”

Section: Introductionmentioning

confidence: 98%

Determining the relative stability of leading-edge vortices on nominally two-dimensional flapping profiles

Wong

Rival

2015

J. Fluid Mech.

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It is hypothesized that the relative stability of leading-edge vortices (LEVs) on flapping profiles can be improved by moderating LEV growth through spanwise vorticity convection and vortex stretching. Moreover, it is hypothesized that the reduced frequency k and profile sweep Λ are critical in predicting relative LEV stability as determined by the aforementioned effects. These hypotheses are then confirmed experimentally with phase-averaged particle image velocimetry (PIV) and three-dimensional particle tracking velocimetry. In particular, more stable LEVs are observed at higher reduced frequencies, which is argued to represent the ratio between the limiting vortex size and the rate of vorticity feeding. The introduction of profile sweep increased both relative LEV stability and spanwise vorticity transport. It is thought that spanwise vorticity transport improved LEV stability by acting as a sink for vorticity generated in the leading-edge shear layer.

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“…Simulations were preformed with a 2D RANS model, and captured the formation of the LEV, but could not accurately capture the reattachment, which has been previously documented in RANS computations of unsteady flows [18]. In a followup paper, a thin flat plate is compared to the SD7003 airfoil, and it is found the geometry can influence the LEV formation and lift forces by promoting earlier separation [19], and experimental studies have by Rival et al [20] have shown a similar trend in a plunging plate of various leading edge geometries. Visbal performed large-eddy simulations at Re = 60, 000 of a plunging SD7003 airfoil at an angle of attack of 8 • , providing a detailed analysis of the LEV flow structure and 3D effects [21].…”

Section: Introductionmentioning

confidence: 99%

Unsteady high-lift mechanisms from heaving flat plate simulations

Franck

Breuer

2017

International Journal of Heat and Fluid Flow

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Flapping animal flight is often modeled as a combined pitching and heaving motion in order to investigate the unsteady flow structures and resulting forces that could augment the animal's lift and propulsive capabilities. This work isolates the heaving motion of flapping flight in order to numerically investigate the flow physics at a Reynolds number of 40,000, a regime typical for large birds and bats and challenging to simulate due to the added complexity of laminar to turbulent transition in which boundary layer separation and reattachment are traditionally more difficult to predict. Periodic heaving of a thin flat plate at fixed angles of attacks of 1, 5, 9, 13, and 18 degrees are simulated using a large-eddy simulation (LES). The heaving motion significantly increases the average lift compared with the steady flow, and also surpasses the quasi-steady predictions due to the formation of a leading edge vortex (LEV) that persists well into the static stall region. The progression of the high-lift mechanisms throughout the heaving cycle is presented over the range of angles of attack. Lift enhancement compared with the equivalent steady state flow was found to be up to 17% greater, and up to 24% greater than that predicted by a quasi-steady analysis. For the range of kinematics explored it is found that maximum lift enhancement occurs at an angle of attack of 13 degrees, with a maximum lift coefficient of 2.1, a mean lift coefficient of 1.04.

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Characteristic length scales for vortex detachment on plunging profiles with varying leading-edge geometry

Cited by 98 publications

References 18 publications

Investigation of vortex development on accelerating spanwise-flexible wings

Investigation of vortex development on accelerating spanwise-flexible wings

Determining the relative stability of leading-edge vortices on nominally two-dimensional flapping profiles

Unsteady high-lift mechanisms from heaving flat plate simulations

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