Scaling of flow separation on a pitching low aspect ratio plate

Yilmaz, Turgut O.; Ol, Michael V.; Rockwell, D.

doi:10.1016/j.jfluidstructs.2010.07.003

Cited by 25 publications

(12 citation statements)

References 17 publications

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“…In the present implementation, a positive-displacement pump with a prescribed volumetric infusion rate introduced the dye through a set of 0.5mm internal-diameter rigid lines glued to the surface of the plate. The positive-displacement method allows for more control than the principal alternative -gravity-feed; for comparison between the two, see Yilmaz et al 20 . For visualizing leading edge vortices, the dye lines run along the plate leading edge, firing outboard.…”

Section: Dye Injectionmentioning

confidence: 99%

Experiments on Pitching Plates: Force and Flowfield Measurements at Low Reynolds Numbers

Granlund

Bernal

2011

49th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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We discuss implementation of prescribed-motion rigs, dye injection and direct force measurement for high frequency, high-amplitude smoothed linear pitch ramps of flat-plate models in a water tunnel. We extend recent results on 2D (wall to wall) flat plates pitching from 0° to 90°, to rectangular and elliptical (Zimmerman planform) plates of aspect ratio 2. Surveying a range of pivot point locations and pitch rates, we compare the development of leading edge vortices, tip vortices and trailing edge vortices, with trends in lift coefficient and drag coefficient history. The lift peak is seen to correlate with the maximum size of the leading edge vortex, prior to its shedding and downstream convection. Tip vortices evolve more slowly than leading edge vortices, in the sense that a tip vortex remains coherent and nearly attached to the wingtip until well past leading edge vortex saturation and shedding. Peak lift is delayed to progressively higher angles of attack as the reduced frequency is increased. And the non-circulatory or apparent-mass forces are evidently additive to the circulatory aerodynamic forces, implying applicability of linear superposition.

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Section: Dye Injectionmentioning

confidence: 99%

Experiments on Pitching Plates: Force and Flowfield Measurements at Low Reynolds Numbers

Granlund

Bernal

2011

49th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…As a first approximation, the magnitude and direction of both velocities are effectively identical (U ∞ = U eff ) for pitching and towing motions (see e.g. Koumoutsakos & Shiels 1996;Yilmaz, Ol & Rockwell 2010;Buchholz, Green & Smits 2011;Hartloper et al 2012). Note that a similar alignment of velocities can be assumed for other unidirectional cases like one-dimensional gusts, as for instance discussed by Afgan et al (2013).…”

Section: Introductionmentioning

confidence: 95%

On the persistence of memory: do initial conditions impact vortex formation?

2013

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An investigation into redistribution of vorticity for rapidly accelerating plates with varying kinematics and initial conditions has been performed. Both threedimensional particle tracking velocimetry and direct force measurements were applied simultaneously. The effective velocity of the feeding shear layer has been identified as the appropriate characteristic velocity rather than the commonly used plunge or free stream velocity. Based on this new normalization for circulation, it has been demonstrated that the existence of initial boundary-layer vorticity on the plunging plate -at least in the near-midplane region -does not contribute to the eventual vortex formation process. In accordance with the literature, however, the tip vortex positioning relative to the plate surface has been identified as an important contributor in the overall force production, particularly once the plate acceleration has ceased.

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“…One expects three-dimensional complexity in LEV evolution for a finite aspect ratio plate accelerating in a steady freestream, as observed for example by Visbal et al (2013) for plunging and Yilmaz et al (2010) for pitching and plunging. In the present case, there is no free stream in the lab-frame.…”

Section: (E)-(f)mentioning

confidence: 99%

“…DeVoria and Ringuette (2012), Jones and Babinsky (2010), Letink andDickinson (2009), Visbal et al (2013) and Yilmaz et al (2010) have documented the importance of the leading edge vortex (LEV) in aerodynamic force production, both in translational and flapping motions and including three-dimensional effects. Jones and Babinsky (2011) offer the suggestion that acceleration of the plate leading edge may promote LEV formation and stability, and inversely, a sharp acceleration of the leading edge followed by a long run of steady translational speed may lead to early LEV detachment.…”

Section: Introductionmentioning

confidence: 99%