How swifts control their glide performance with morphing wings

Lentink, David; Mueller, U. K.; Stamhuis, Eize; Gestel, W. van; Leeuwen, J.L. van; Videler, John J.; Kat, Roeland de; Veldhuis, L.L.M.; Henningsson, Per; Hedenström, Anders

doi:10.1016/j.cbpa.2007.01.204

Cited by 48 publications

(66 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Further, a direct analogy between LEVs on swept and revolving wings does not seem to hold for equally shaped wings operating at equally low Reynolds numbers, because we did not observe stable LEVs or force augmentation for swept fruit fly wings (Figs 1 and 2). In other experiments with high aspect ratio swept bird wings (Apus apus) a stable LEV was found (Videler et al, 2004;Lentink et al, 2007), but no significant force augmentation (lift coefficients lower than one) for Ro=3.2 (s.d.=1.18,N=117). The circles with a black outline represent values that are directly based on the aspect ratio of one wing.…”

Section: Comparing Old and New Lev Stability Hypothesesmentioning

confidence: 75%

See 1 more Smart Citation

Rotational accelerations stabilize leading edge vortices on revolving fly wings

Lentink

Dickinson

2009

Journal of Experimental Biology

458

474

View full text Add to dashboard Cite

SUMMARYThe aerodynamic performance of hovering insects is largely explained by the presence of a stably attached leading edge vortex (LEV) on top of their wings. Although LEVs have been visualized on real, physically modeled, and simulated insects, the physical mechanisms responsible for their stability are poorly understood. To gain fundamental insight into LEV stability on flapping fly wings we expressed the Navier-Stokes equations in a rotating frame of reference attached to the wing's surface. Using these equations we show that LEV dynamics on flapping wings are governed by three terms: angular, centripetal and Coriolis acceleration. Our analysis for hovering conditions shows that angular acceleration is proportional to the inverse of dimensionless stroke amplitude, whereas Coriolis and centripetal acceleration are proportional to the inverse of the Rossby number. Using a dynamically scaled robot model of a flapping fruit fly wing to systematically vary these dimensionless numbers, we determined which of the three accelerations mediate LEV stability. Our force measurements and flow visualizations indicate that the LEV is stabilized by the 'quasi-steady' centripetal and Coriolis accelerations that are present at low Rossby number and result from the propeller-like sweep of the wing. In contrast, the unsteady angular acceleration that results from the back and forth motion of a flapping wing does not appear to play a role in the stable attachment of the LEV. Angular acceleration is, however, critical for LEV integrity as we found it can mediate LEV spiral bursting, a high Reynolds number effect. Our analysis and experiments further suggest that the mechanism responsible for LEV stability is not dependent on Reynolds number, at least over the range most relevant for insect flight (100

show abstract

Section: Comparing Old and New Lev Stability Hypothesesmentioning

confidence: 75%

“…12,000<Re<77,000 (Lentink et al, 2007). This suggests that a direct analogy between LEVs on swept and revolving wings does not hold at higher Reynolds numbers either.…”

Section: Comparing Old and New Lev Stability Hypothesesmentioning

confidence: 97%

Rotational accelerations stabilize leading edge vortices on revolving fly wings

Lentink

Dickinson

2009

Journal of Experimental Biology

458

474

View full text Add to dashboard Cite

show abstract

“…2a). These differences in lifting wing surface area were taken into account using speed-specific L and -D (see Methods) 21 . Results also show that Microraptor would have aerodynamically (expressed by the glide ratio) performed best with the sprawled-leg configuration for all values of speedspecific aerodynamic force coefficient (SCR) (Fig.…”

Section: Resultsmentioning

confidence: 99%

Aerodynamic performance of the feathered dinosaur Microraptor and the evolution of feathered flight

et al. 2013

View full text Add to dashboard Cite

Understanding the aerodynamic performance of feathered, non-avialan dinosaurs is critical to reconstructing the evolution of bird flight. Here we show that the Early Cretaceous five-winged paravian Microraptor is most stable when gliding at high-lift coefficients (low lift/ drag ratios). Wind tunnel experiments and flight simulations show that sustaining a high-lift coefficient at the expense of high drag would have been the most efficient strategy for Microraptor when gliding from, and between, low elevations. Analyses also demonstrate that anatomically plausible changes in wing configuration and leg position would have made little difference to aerodynamic performance. Significant to the evolution of flight, we show that Microraptor did not require a sophisticated, 'modern' wing morphology to undertake effective glides. This is congruent with the fossil record and also with the hypothesis that symmetric 'flight' feathers first evolved in dinosaurs for non-aerodynamic functions, later being adapted to form lifting surfaces.

show abstract

“…A miniaturized GPS device was used to investigate the navigation strategy of Homing pigeons (10,11). Very recently, simulations were used to calculate the flight efficiency of the huge volant bird Argentavis magnificiens from the upper Miocene (12), and wind tunnel experiments and modeling were carried out to understand how swifts use morphing wings to control their glide performance (13).…”

mentioning

confidence: 99%

Comparing bird and human soaring strategies

Ákos

Nagy

Vicsek

2008

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Gliding saves much energy, and to make large distances using only this form of flight represents a great challenge for both birds and people. The solution is to make use of the so-called thermals, which are localized, warmer regions in the atmosphere moving upwards with a speed exceeding the descent rate of bird and plane. Whereas birds use this technique mainly for foraging, humans do it as a sporting activity. Thermalling involves efficient optimization including the skilful localization of thermals, trying to guess the most favorable route, estimating the best descending rate, etc. In this study, we address the question whether there are any analogies between the solutions birds and humans find to handle the above task. High-resolution track logs were taken from thermalling falcons and paraglider pilots to determine the essential parameters of the flight patterns. We find that there are relevant common features in the ways birds and humans use thermals. In particular, falcons seem to reproduce the MacCready formula widely used by gliders to calculate the best slope to take before an upcoming thermal.D uring long-term gliding, birds and people make use of the so-called thermals, which are spatially and temporally localized parts of the atmosphere typically moving upwards with a speed in the range of 1-5 m/s. After locating it, a glider remains within a thermal by circling until the desired height is attained. Then, a more or less straight advancing, but sinking, phase follows until the next thermal is reached. Paraglider pilots use watching the birds thermalling nearby for finding the next thermal, and sometimes the birds seem to follow the glider (Fig. 1A). Learning about previously unavailable details of this fascinating process can lead us to a better understanding of the main features of flight trajectories and optimization tactics. To locate the best route to a distant point, at least in the case of human gliders who typically use specific devices assisting in making the best decisions, is a complex mental process involving both calculations and intuition. We consider thermalling as one of the scarce examples when an intellectually driven activity of humans is apparently so closely related to the actual behavior of an animal. Several interesting questions emerge: Does the obvious size difference result in a different flight pattern and speed? Are the common tricks the same or are there alternative successful tactics?Because collecting data on the soaring flight of birds is a rather difficult task, several techniques have been used for this purpose. A powered sailplane with a camera and ornithodolite techniques were used to determine the polar curves and the circling radius of various birds (1, 2). Gliding of four different bird species was investigated by radar during their migration (3, 4). An altimeter with a satellite transmitter was used in similar studies on the American White pelicans in Nevada (5). A further project demonstrated that the Magnificent frigate bird is thermalling continuously, day an...

show abstract

How swifts control their glide performance with morphing wings

Cited by 48 publications

References 0 publications

Rotational accelerations stabilize leading edge vortices on revolving fly wings

Rotational accelerations stabilize leading edge vortices on revolving fly wings

Aerodynamic performance of the feathered dinosaur Microraptor and the evolution of feathered flight

Comparing bird and human soaring strategies

Contact Info

Product

Resources

About