Three-dimensional flow structures and evolution of the leading-edge vortices on a flapping wing

Yuan, Lü; Shen, Gong Xin

doi:10.1242/jeb.010652

Cited by 84 publications

(54 citation statements)

References 43 publications

(115 reference statements)

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“…At least in bats, these vortices were connected with spanwise vortices shed as a result of changes in circulation about the wing throughout the wingbeat [11]. When lowering the iso-value of the Q-criteria in our plots, which is used to identify vortices [35], we also find these spiralling vortices to be connected to spanwise vortices, which is in agreement with findings for bats [11]. This is consistent with a continuous change in bound circulation found during the wingbeat in birds [51].…”

Section: Wakesmentioning

confidence: 95%

Mechanical power curve measured in the wake of pied flycatchers indicates modulation of parasite power across flight speeds

Johansson¹,

Maeda²,

Henningsson³

et al. 2018

J. R. Soc. Interface.

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How aerodynamic power required for animal flight varies with flight speed determines optimal speeds during foraging and migratory flight. Despite its relevance, aerodynamic power provides an elusive quantity to measure directly in animal flight. Here, we determine the aerodynamic power from wake velocity fields, measured using tomographical particle image velocimetry, of pied flycatchers flying freely in a wind tunnel. We find a shallow U-shaped power curve, which is flatter than expected by theory. Based on how the birds vary body angle with speed, we speculate that the shallow curve results from increased body drag coefficient and body frontal area at lower flight speeds. Including modulation of body drag in the model results in a more reasonable fit with data than the traditional model. From the wake structure, we also find a single starting vortex generated from the two wings during the downstroke across flight speeds (1–9 m s −1 ). This is accomplished by the arm wings interacting at the beginning of the downstroke, generating a unified starting vortex above the body of the bird. We interpret this as a mechanism resulting in a rather uniform downwash and low induced power, which can help explain the higher aerodynamic performance in birds compared with bats.

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Section: Wakesmentioning

confidence: 95%

Mechanical power curve measured in the wake of pied flycatchers indicates modulation of parasite power across flight speeds

Johansson¹,

Maeda²,

Henningsson³

et al. 2018

J. R. Soc. Interface.

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show abstract

“…Two frame-straddling CCD cameras (PowerView Plus, 4008 3 2672 pixels) with lenses (Micro Nikkor 60 mm, Nikon, Japan) were used to capture the particle displacement. Asymmetric SPIV arrangement 43 was utilized, and the lenses and the cameras were mounted on an electromechanical translation apparatus to satisfy the Scheimpflug condition, which requires the measurement, image, and lens principle planes to intersect at a common point, as shown in Figure 1.…”

Section: Spiv Techniquementioning

confidence: 99%

Stereo‐PIV experiments and large eddy simulations of flow fields in stirred tanks with Rushton and curved‐Blade turbines

Song

Bao

et al. 2013

AIChE Journal

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The flow characteristics in pilot-scale stirred tanks with Rushton and curved-blade turbines were investigated by using stereoscopic particle image velocimetry (SPIV) experiments and large eddy simulation (LES) methods. The velocity and turbulent kinetic energy (TKE) in the impeller discharge regions were carefully resolved with a high resolution SPIV system, and the detailed phase-resolved velocity and TKE profiles were used to validate the LES results. The effects of Reynolds number and blade shape on the flow characteristics were discussed. The LES results of velocity, TKE, and the evolution of trailing vortices were compared with the SPIV experimental data, and good agreement was obtained at various phase angles. The effects of subgrid scale model and hybrid grid with different mesh resolutions on the LES results were investigated. LES is a computationally affordable method for the accurate predictions of the complex flow fields in pilot-scale stirred tanks is presented.

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“…Lu and Shen (Lu and Shen, 2008) studied experimentally the 3D flow structures and evolution of the LEV on a flapping wing in the hovering condition. Their results showed that the LEV system is a collection of four vortical elements: one primary vortex and three minor vortices.…”

Section: Introductionmentioning

confidence: 99%

Stereoscopic particle image velocimetry measurements of the three-dimensional flow field of a descending autorotating Mahogany seed (Swietenia macrophylla)

Salcedo

Treviño

Vargas

et al. 2013

Journal of Experimental Biology

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SUMMARYAn experimental investigation of near field aerodynamics of wind dispersed rotary seeds has been performed using stereoscopic digital particle image velocimetry (DPIV). The detailed three-dimensional flow structure of the leading-edge vortex (LEV) of autorotating mahogany seeds (Swietenia macrophylla) in a low-speed vertical wind tunnel is revealed for the first time. The results confirm that the presence of strong spanwise flow and strain produced by centrifugal forces through a spiral vortex are responsible for the attachment and stability of the LEV, with its core forming a cone pattern with a gradual increase in vortex size. The LEV appears at 25% of the wingspan, increases in size and strength outboard along the wing, and reaches its maximum stability and spanwise velocity at 75% of the wingspan. At a region between 90 and 100% of the wingspan, the strength and stability of the vortex core decreases and the LEV re-orientation/inflection with the tip vortex takes place. In this study, the instantaneous flow structure and the instantaneous velocity and vorticity fields measured in planes parallel to the free stream direction are presented as contour plots using an inertial and a non-inertial frame of reference. Results for the mean aerodynamic thrust coefficients as a function of the Reynolds number are presented to supplement the DPIV data.

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Three-dimensional flow structures and evolution of the leading-edge vortices on a flapping wing

Cited by 84 publications

References 43 publications

Mechanical power curve measured in the wake of pied flycatchers indicates modulation of parasite power across flight speeds

Mechanical power curve measured in the wake of pied flycatchers indicates modulation of parasite power across flight speeds

Stereo‐PIV experiments and large eddy simulations of flow fields in stirred tanks with Rushton and curved‐Blade turbines

Stereoscopic particle image velocimetry measurements of the three-dimensional flow field of a descending autorotating Mahogany seed (Swietenia macrophylla)

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