Three-dimensional flow visualization and vorticity dynamics in revolving wings

Cheng, Bo; Sane, Sanjay P.; Barbera, Giovanni; Troolin, Dan; Strand, T. E.; Deng, Xinyan

doi:10.1007/s00348-012-1423-0

Cited by 57 publications

(52 citation statements)

References 26 publications

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“…The Reynolds numbers considered in this study are assumed to be sufficiently large so that the time scales of diffusion are much slower than the time scales associated with LEV growth and convection. This conclusion is also supported by Cheng et al (2013) where the diffusion terms for similar Reynolds numbers were deemed negligible. This leaves two terms, which contribute to vortex growth: the convection term and the tilting/stretching term.…”

Section: Introductionsupporting

confidence: 68%

Investigation of vortex development on accelerating spanwise-flexible wings

Jain

Wong

Rival

2015

Journal of Fluids and Structures

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Section: Introductionsupporting

confidence: 68%

Investigation of vortex development on accelerating spanwise-flexible wings

Jain

Wong

Rival

2015

Journal of Fluids and Structures

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“…It was concluded that spanwise vorticity convection was insufficient to balance vorticity production, and that the large residual in the vorticity balance must be accounted for by vorticity annihilation. Similarly, Cheng et al (2013) found that spanwise vorticity convection was negligible relative to convection in the streamwise and wall-normal directions. However, in natural swimming and flight, the full benefit of a stable LEV is realized when the LEV is maintained for at least one half-stroke of motion, rather than an indefinite period.…”

Section: Introductionmentioning

confidence: 93%

“…rotating cases often exhibit vortex stability, where both the convection speed of the LEV relative to the profile and the growth rate of the LEV are near zero, as observed by Ozen & Rockwell (2012), Cheng et al (2013) and Wojcik & Buchholz (2014), to name a few.…”

Section: Introductionmentioning

confidence: 95%

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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“…By comparing different terms in the vorticity equation, we found convection in tangential and vertical directions are responsible for a majority of the vorticity change, where those in the spanwise direction are negligible. In comparison, vortex tilting and stretching have a smaller effect than convection, but reduce the radial vorticity accumulated by vertical convection in a particular region [35].…”

Section: Discussionmentioning

confidence: 99%