Adaptive control of turbulence intensity is accelerated by frugal flow sampling

Quinn, Daniel; Halder, Yous van; Lentink, David

doi:10.1098/rsif.2017.0621

Cited by 3 publications

(2 citation statements)

References 92 publications

(149 reference statements)

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“…The impact of atmospheric turbulence on flying animals represents an important frontier [1][2][3], as the effects of turbulence on flight energetics and route selection are far less studied than the effects of wind [4,5]. Turbulence is broadly defined as a measure of rapid changes in wind velocity at small scales and is mainly driven by shear forcing or thermal heating, although it can also be generated by warm and cold fronts.…”

Section: Introductionmentioning

confidence: 99%

Estimating fine-scale changes in turbulence using the movements of a flapping flier

Lempidakis

Ross

Quetting

et al. 2022

J. R. Soc. Interface.

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All animals that operate within the atmospheric boundary layer need to respond to aerial turbulence. Yet little is known about how flying animals do this because evaluating turbulence at fine scales (tens to approx. 300 m) is exceedingly difficult. Recently, data from animal-borne sensors have been used to assess wind and updraft strength, providing a new possibility for sensing the physical environment. We tested whether highly resolved changes in altitude and body acceleration measured onboard solo-flying pigeons (as model flapping fliers) can be used as qualitative proxies for turbulence. A range of pressure and acceleration proxies performed well when tested against independent turbulence measurements from a tri-axial anemometer mounted onboard an ultralight flying the same route, with stronger turbulence causing increasing vertical displacement. The best proxy for turbulence also varied with estimates of both convective velocity and wind shear. The approximately linear relationship between most proxies and turbulence levels suggests this approach should be widely applicable, providing insight into how turbulence changes in space and time. Furthermore, pigeons were able to fly in levels of turbulence that were unsafe for the ultralight, paving the way for the study of how freestream turbulence affects the costs and kinematics of animal flight.

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Section: Introductionmentioning

confidence: 99%

Estimating fine-scale changes in turbulence using the movements of a flapping flier

Lempidakis

Ross

Quetting

et al. 2022

J. R. Soc. Interface.

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show abstract

“…The impact of atmospheric turbulence on flying animals represents an important frontier (Bomphrey and Godoy-Diana, 2018, Laurent et al, 2021, Quinn et al, 2017, as the effects on flight energetics and route selection are far less studied than those of wind Alerstam, 1995, Liechti, 2006). Turbulence is broadly defined as a measure of rapid changes in wind velocity at small scales and is driven by mechanical forcing or surface heating.…”

Section: Introductionmentioning

confidence: 99%

The implications of costly airflows for space-use and movement decisions in birds

Lempidakis¹

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The behavioural ecology of flight has largely considered how birds respond to mean flow conditions, but it is the gusty or extreme airflows that are likely to be particularly challenging. This thesis addresses this, examining the strategies birds use to negotiate turbulence over land, and exceedingly strong winds at sea. I first develop a method for sensing turbulence at fine scales using data collected onboard the animals themselves, taking homing pigeons (Columba livia) as model flapping fliers. Fine scale variation in the flight altitude and body displacement emerged as effective proxies of turbulence. I then assess the impact of freestream turbulence on flapping fliers and find that pigeons adapted their wingbeat kinematics (frequency and amplitude) to increase their flight stability in response to turbulence, but did so without a clear increase in flight effort. In my final two chapters I examine the responses of two seabird species to strong winds, first at sea, and then on land. Specifically, I investigate how streaked shearwaters (Calonectris leucomelas) respond to tropical cyclones, and how common guillemots (Uria aalge) select their breeding cliffs in relation to airflow conditions. I find that shearwaters fly towards the eye of the storm. This tendency increases with cyclone intensity and may enable birds to avoid strong onshore winds and reduce the associated risks of forced landings and/ or injury. Finally, computational fluid dynamics models reveal that guillemots select breeding cliffs that are sheltered from wind and storm conditions, rather than from the mean wind alone, or heat stress. This model of habitat selection could also predict habitat use across islands. Overall, this highlights the varied and sometimes surprising capacities of birds to cope with extreme and variable airflows and operate in areas that are, as yet, inaccessible to aircraft.

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How flight feathers stick together to form a continuous morphing wing

Matloff

Chang

Feo

et al. 2020

Science

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Variable feather overlap enables birds to morph their wings, unlike aircraft. They accomplish this feat by means of elastic compliance of connective tissue, which passively redistributes the overlapping flight feathers when the skeleton moves to morph the wing planform. Distinctive microstructures form “directional Velcro,” such that when adjacent feathers slide apart during extension, thousands of lobate cilia on the underlapping feathers lock probabilistically with hooked rami of overlapping feathers to prevent gaps. These structures unlock automatically during flexion. Using a feathered biohybrid aerial robot, we demonstrate how both passive mechanisms make morphing wings robust to turbulence. We found that the hooked microstructures fasten feathers across bird species except silent fliers, whose feathers also lack the associated Velcro-like noise. These findings could inspire innovative directional fasteners and morphing aircraft.

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Adaptive control of turbulence intensity is accelerated by frugal flow sampling

Cited by 3 publications

References 92 publications

Estimating fine-scale changes in turbulence using the movements of a flapping flier

Estimating fine-scale changes in turbulence using the movements of a flapping flier

The implications of costly airflows for space-use and movement decisions in birds

How flight feathers stick together to form a continuous morphing wing

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