Aerodynamic forces acting on birds during flight: A comparative study of a shorebird, songbird and a strigiform

Nafi, Asif Shahriar; Ben-Gida, Hadar; Guglielmo, Christopher G.; Gurka, Roi

doi:10.1016/j.expthermflusci.2019.110018

Cited by 14 publications

(10 citation statements)

References 38 publications

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“…This is due to the fact that all measurements were extracted from perch-toperch flight rather than steady flight, limiting the statistical sample to a few flapping cycles and increasing the uncertainties in estimating the aerodynamic forces. Nevertheless, the prediction of the drag force for the present case is in line with experimental observations (Nafi et al 2020). The changes in drag over the wingbeat cycle include an apparent negative drag during the transition phase, which has been reported by Ben-Gida et al (2013), associating it to the unsteady drag contribution.…”

Section: Discussionsupporting

confidence: 91%

“…The drag force remains almost constant throughout the entire wingbeat except during the transition phase from upstroke to downstroke, where a sharp drop is observed. This observation is in qualitative agreement with the experimental observations by Nafi et al (2020), where the variation of the drag force extracted from PIV measurements in the wake of a boobook owl flying freely and steadily in a wind tunnel was reported. The mean value of the drag coefficient is C mean D ¼ 0:12.…”

Section: Wake Structure and Aerodynamic Forcessupporting

confidence: 92%

“…Direct measurements of aerodynamic forces during in vivo bird flight are very challenging. Lawley et al (2019) and Nafi et al (2020) reported near-wake flow measurements for a boobook owl freely flying in a climatic wind tunnel. The latter study verified that in comparison to other birds, the owl aerodynamic performance was low, while the former demonstrated strong turbulent suppression in the wake, which can potentially muffle its aeroacoustic (aerodynamic noise) signature.…”

Section: Introductionmentioning

confidence: 99%

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Direct Numerical Simulations of a Great Horn Owl in Flapping Flight

Beratlis

Capuano

Krishnan

et al. 2020

Integrative and Comparative Biology

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The fluid dynamics of owls in flapping flight is studied by coordinated experiments and computations. The great horned owl was selected, which is nocturnal, stealthy, and relatively large sized raptor. On the experimental side, perch-to-perch flight was considered in an open wind tunnel. The owl kinematics were captured with multiple cameras from different view angles. The kinematic extraction was central in driving the computations, which were designed to resolve all significant spatio-temporal scales in the flow with an unprecedented level of resolution. The wing geometry was extracted from the planform image of the owl wing and a three-dimensional model, the reference configuration, was reconstructed. This configuration was then deformed in time to best match the kinematics recorded during flights utilizing an image-registration technique based on the large deformation diffeomorphic metric mapping framework. All simulations were conducted using an eddy-resolving, high-fidelity, solver, where the large displacements/deformations of the flapping owl model were introduced with an immersed boundary formulation. We report detailed information on the spatio-temporal flow dynamics in the near wake including variables that are challenging to measure with sufficient accuracy, such as aerodynamic forces. At the same time our results indicate that high-fidelity computations over smooth wings may have limitations in capturing the full range of flow phenomena in owl flight. The growth and subsequent separation of the laminar boundary layers developing over the wings in this Reynolds number regime is sensitive to the surface micro-features that are unique to each specie.

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Section: Discussionsupporting

confidence: 91%

Section: Wake Structure and Aerodynamic Forcessupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Direct Numerical Simulations of a Great Horn Owl in Flapping Flight

Beratlis

Capuano

Krishnan

et al. 2020

Integrative and Comparative Biology

Self Cite

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“…It is noteworthy that drag coefficient is computed for a sequence of velocity maps, and therefore it does not require a priori information of the reconstructed wake. The variation of the cumulative circulatory lift coefficient ∆C lcirc can be estimated from the PIV velocity vector fields based on Stalnov et al [24], Ben-Gida et al [25] and Nafi et al [26]. Any fluid motion around a body is accompanied by the shedding of vortices into the wake.…”

Section: Conflict Of Interestmentioning

confidence: 99%

OpenPIV-MATLAB — An open-source software for particle image velocimetry; test case: Birds’ aerodynamics

2020

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“…And it is not easy to make reliable predictions of transient aerodynamic forces using unsteady aerodynamics theory. Nafi et al [8] estimated the aerodynamic forces on freely flying birds by analyzing the wingbeat kinematics and near-wake flow measurements using longduration time-resolved particle image velocimetry. Lentink et al [9] developed a method to measure aerodynamic forces on flying animals and biomimetic robots.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of the Aerodynamics of a Hovering Hummingbird’s Wing with Dynamic Morphing

Dong

Song

Xue

et al. 2022

International Journal of Aerospace Engineering

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To deepen our understanding of the aerodynamics by which hummingbirds use flexible wings to hover efficiently during flapping flight, a three-dimensional wing model with dynamic morphing was developed according to the morphological and kinematic data of a hovering hummingbird’s wing. Navier-Stokes equations were solved on a dynamically deforming grid to study wing aerodynamics. In numerical simulations, boundary-based smoothing and overset methodologies were used in combination to update the interior nodes of cells in the computational domain, allowing those nodes to accommodate the motion of the flexible wall. This study showed that the leading edge vortex (LEV) attached to the wing was stable during the downstroke but extremely unstable and shed continuously during the upstroke. In the results of the downward stroke, the different vortices separated from the surface and formed a vortex ring. The difference is that the leading edge vortex induced a vortex ring near the root and a smaller and weaker vortex ring near the wingtip during the upstroke. A significant enhancement in aerodynamic forces was found during the downstroke, along with a large number of power consumptions. We found that the asymmetry in the time-averaged vertical force between the two half strokes was 3.5, and the value was higher than that reported earlier. Aerodynamic force coefficients and efficiency matched well with those of another hummingbird wing (the ruby-throated hummingbird). It is worth noting that hummingbirds can maintain a similar wingtip speed by flapping their wings, but different strategies are adapted to hover efficiently due to the differences in size and body weight. The results of this study help to better understand the aerodynamics of the hovering hummingbird.

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Aerodynamic forces acting on birds during flight: A comparative study of a shorebird, songbird and a strigiform

Cited by 14 publications

References 38 publications

Direct Numerical Simulations of a Great Horn Owl in Flapping Flight

Direct Numerical Simulations of a Great Horn Owl in Flapping Flight

OpenPIV-MATLAB — An open-source software for particle image velocimetry; test case: Birds’ aerodynamics

Numerical Study of the Aerodynamics of a Hovering Hummingbird’s Wing with Dynamic Morphing

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