Ventral-clap modes of hovering passerines

Chang, Yung-Chung; Ting, Shang-Chieh; Su, Jian-Yuan; Soong, Chyi–Yeou; Yang, Jing‐Tang

doi:10.1103/physreve.87.022707

Cited by 9 publications

(9 citation statements)

References 23 publications

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“…In particular, the peak wingtip velocity in the finch occurs during this phase, and may in fact contribute to the initial creation of circulation. Two passerine species demonstrate clap kinematics at the transition from downstroke to upstroke (Chang et al, 2013), so it is feasible that a similar pattern occurs during the upstroke to downstroke transition. Further work with high-speed, stereo PIV is necessary to explore this hypothesis.…”

Section: Discussionmentioning

confidence: 99%

“…Theory and empirical measurements with flapper models both indicate a boost in force production via this mechanism (Ellington, 1984;Lehmann et al, 2005). Among birds, there exists aerodynamic evidence that Japanese white-eye (Zosterops japonicus) and Gouldian finch (Erythrura gouldiae) capitalize on a ventral clap, wherein the wings are brought together beneath the body to contribute to the downwash (Chang et al, 2013). Here, we differentiate between a clap and fling versus a clap and peel, as defined by Miller and Peskin (2009): we define a clap and fling as minimal flexibility in a rigid wing structure, wherein changes in shape are from external mechanisms, such as aerodynamic loading and inertia; clap and peel, then, has flexibility spanwise and chordwise along the wing, and shape changes are both passive and active via musculoskeletal control.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, the observed kinematic patterns during slow flight have prompted the well-established prediction that the upstroke is aerodynamically inactive, halving the amount of time during a wingbeat that a bird can produce useful forces. Few direct measures of the kinematics and aerodynamics of upstroke in slow flight exist, however (Chang et al, 2013;Hedenström et al, 2006;Lentink et al, 2015;Muijres et al, 2012a,b,c;Spedding et al, 2003a). Most studies of takeoff flight focus on the immediate transition from legs to wings (Berg and Biewener, 2010;Earls, 2000;Provini et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Kinematics and aerodynamics of avian upstrokes during slow flight

Crandell

Tobalske

2015

Journal of Experimental Biology

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Slow flight is extremely energetically costly per unit time, yet highly important for takeoff and survival. However, at slow speeds it is presently thought that most birds do not produce beneficial aerodynamic forces during the entire wingbeat: instead they fold or flex their wings during upstroke, prompting the long-standing prediction that the upstroke produces trivial forces. There is increasing evidence that the upstroke contributes to force production, but the aerodynamic and kinematic mechanisms remain unknown. Here, we examined the wingbeat cycle of two species: the diamond dove (Geopelia cuneata) and zebra finch (Taeniopygia guttata), which exhibit different upstroke styles -a wingtip-reversal and flexed-wing upstroke, respectively. We used a combination of particle image velocimetry and near-wake streamline measures alongside detailed 3D kinematics. We show that during the middle of the wingtip-reversal upstroke, the hand-wing has a high angular velocity (15.3±0.8 deg ms ). The flexed-wing upstroke, in contrast, has low wingtip speed during mid-upstroke. Instead, later in the stroke cycle, during the transition from upstroke to downstroke, it exhibits higher angular velocities (45.5±13.8 deg ms ). In contrast, the flexed-wing upstroke imparts minimal momentum. Clap and peel in the dove enhances the time course for circulation production on the wings, and provides new evidence of convergent evolution on time-varying aerodynamic mechanisms during flapping in insects and birds.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Kinematics and aerodynamics of avian upstrokes during slow flight

Crandell

Tobalske

2015

Journal of Experimental Biology

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“…In fact, there is no investigation that reports LEV formation, which is one of the most important force enhancement features for the lift-based mechanism in insects, birds and bats (Ellington et al 1996;Van Den Berg & Ellington 1997;Birch & Dickinson 2001;Sane 2003;Videler, Stamhuis & Povel 2004;Muijres et al 2008;Lentink & Dickinson 2009b;Chang et al 2013;Thielicke & Stamhuis 2015). Borazjani & Daghooghi (2013) reported for the first time the LEV reattachment on the fish's tail, enhancing the thrust generation by the tail, in the inertial flow regime at Strouhal numbers commonly seen in fish swimming.…”

Section: Introductionmentioning

confidence: 96%

Hydrodynamics of swimming in stingrays: numerical simulations and the role of the leading-edge vortex

et al. 2016

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Stingrays, in contrast with many other aquatic animals, have flattened disk-shaped bodies with expanded pectoral 'wings', which are used for locomotion in water. To discover the key features of stingray locomotion, large-eddy simulations of a self-propelled stingray, modelled closely after the freshwater stingray, Potamotrygon orbignyi, are performed. The stingray's body motion was prescribed based on three-dimensional experimental measurement of wing and body kinematics in live stingrays at two different swimming speeds of 1.5 and 2.5L s −1 (L is the disk length of the stingray). The swimming speeds predicted by the self-propelled simulations were within 12 % of the nominal swimming speeds in the experiments. It was found that the fast-swimming stingray (Reynolds number Re = 23 000 and Strouhal number St = 0.27) is approximately 12 % more efficient than the slow-swimming one (Re = 13 500, St = 0.34). This is related to the wake of the fast-and slow-swimming stingrays, which was visualized along with the pressure on the stingray's body. A horseshoe vortex was discovered to be present at the anterior margin of the stingray, creating a low-pressure region that enhances thrust for both fast and slow swimming speeds. Furthermore, it was found that a leading-edge vortex (LEV) on the pectoral disk of swimming stingrays generates a low-pressure region in the fast-swimming stingray, whereas the low-and high-pressure regions in the slow-swimming one are in the back half of the wing and not close to any vortical structures. The undulatory motion creates thrust by accelerating the adjacent fluid (the added-mass mechanism), which is maximized in the back of the wing because of higher undulations and velocities in the back. However, the thrust enhancement by the LEV occurs in the front portion of the wing. By computing the forces on the front half and the back half of the wing, it was found that the contribution of the back half of the wing to thrust in a slow-swimming stingray is several-fold higher than in the fast-swimming one. This indicates that the LEV enhances thrust in fast-swimming stingrays and improves the efficiency of swimming.

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“…As recent studies have shown, the aerodynamic mechanisms responsible for the generation of forces during bird flight deviate from the steady flow conditions that are generally assumed for airplane wings: lift-enhancing flow features have been found on the flapping wings of a hovering hummingbird (Warrick, Tobalske & Powers 2005), a robotic goose (Hubel & Tropea 2010), and during the slow-speed flight of a passerine (Muijres, Johansson & Hedenstroem 2012;Chang et al 2013).…”

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confidence: 97%

The influence of wing morphology on the three-dimensional flow patterns of a flapping wing at bird scale

Thielicke

Stamhuis

2015

J. Fluid Mech.

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The effect of airfoil design parameters, such as airfoil thickness and camber, are well understood in steady-state aerodynamics. But this knowledge cannot be readily applied to the flapping flight in insects and birds: flow visualizations and computational analyses of flapping flight have identified that in many cases, a leading-edge vortex (LEV) contributes substantially to the generation of aerodynamic force. In flapping flight, very high angles of attack and partly separated flow are common features. Therefore, it is expected that airfoil design parameters affect flapping wing aerodynamics differently. Existing studies have focused on force measurements, which do not provide sufficient insight into the dominant flow features. To analyse the influence of wing morphology in slow-speed bird flight, the time-resolved three-dimensional flow field around different flapping wing models in translational motion at a Reynolds number of 22 000 < Re < 26 000 was studied. The effect of several Strouhal numbers (0.2 < St < 0.4), camber and thickness on the flow morphology and on the circulation was analysed. A strong LEV was found on all wing types at high St. The vortex is stronger on thin wings and enhances the total circulation. Airfoil camber decreases the strength of the LEV, but increases the total bound circulation at the same time, due to an increase of the 'conventional' bound circulation at the inner half of the wing. The results provide new insights into the influence of airfoil shape on the LEV and force generation at low Re. They contribute to a better understanding of the geometry of vertebrate wings, which seem to be optimized to benefit from LEVs in slow-speed flight.

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Ventral-clap modes of hovering passerines

Cited by 9 publications

References 23 publications

Kinematics and aerodynamics of avian upstrokes during slow flight

Kinematics and aerodynamics of avian upstrokes during slow flight

Hydrodynamics of swimming in stingrays: numerical simulations and the role of the leading-edge vortex

The influence of wing morphology on the three-dimensional flow patterns of a flapping wing at bird scale

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