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Smirnova KP, Frill MA, Warner SE, Cheney JA. Shape change in the saddle region of the equine back during trot and walk. J R Soc Interface 2024; 21:20230644. [PMID: 38916112 DOI: 10.1098/rsif.2023.0644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 05/01/2024] [Indexed: 06/26/2024] Open
Abstract
Equine back pain is prevalent among ridden horses and is often attributed to poor saddle fit. An alternative explanation is that saddle fits are technically good but fit to the wrong configuration. Saddles are fit for the standing horse, but much of the time ridden is instead spent locomoting when the back experiences the greatest peak forces. We used an array of cameras to reconstruct the surface of the back and its movement during trot, walk and standing for five horses. We verified the setup's accuracy by reconstructing a laser-scanned life-sized model horse. Our reconstructions demonstrate that saddles sit within a large, relatively low-mobile region of the back. However, saddles do sit adjacent to the highly mobile withers, which demands care in positioning and design around this important region. Critically, we identified that saddle curvature between standing and moving horses is substantially different, where trotting and walking horses have flatter backs than their standing configurations. Saddles designed around the locomoting configuration of horses may improve horse welfare by being better fit and decreasing the focal pressures applied by saddles.
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Affiliation(s)
| | | | | | - Jorn A Cheney
- Royal Veterinary College , Hatfield AL9 7TA, UK
- School of Biological Sciences, University of Southampton , Southampton SO17 1BJ, UK
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2
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Stanton SC. Shoulder viscoelasticity in a raptor-inspired model alleviates instability and enhances passive gust rejection. BIOINSPIRATION & BIOMIMETICS 2024; 19:046006. [PMID: 38663419 DOI: 10.1088/1748-3190/ad43a2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Accepted: 04/25/2024] [Indexed: 05/12/2024]
Abstract
Recent experiments with gliding raptors reveal a perplexing dichotomy: remarkably resilient gust rejection, but, at the same time, an exceptionally high degree of longitudinal instability. To resolve this incompatibility, a multiple degree of freedom model is developed with minimal requisite complexity to examine the hypothesis that the bird shoulder joint may embed essential stabilizing and preflexive mechanisms for rejecting rapid perturbations while simplifying and reducing control effort. Thus, the formulation herein is centrally premised upon distinct wing pitch and body pitch angles coupled via a Kelvin-Voigt viscoelastic shoulder joint. The model accurately exhibits empirical gust response of an unstable gliding raptor, generates biologically plausible equilibrium configurations, and the viscoelastic shoulder coupling is shown to drastically alleviate the high degree of instability predicted by conventional linear flight dynamics models. In fact, stability analysis of the model predicts a critical system timescale (the time to double amplitude of a pitch divergence mode) that is commensurate within vivomeasured latency of barn owls (Tyto alba). Active gust mitigation is studied by presupposing the owl behaves as an optimal controller. The system is under-actuated and the feedback control law is resolved in the controllable subspace using a Kalman decomposition. Importantly, control-theoretic analysis precisely identifies what discrete gust frequencies may be rapidly and passively rejected versus disturbances requiring feedback control intervention.
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Affiliation(s)
- Samuel C Stanton
- Department of Aeronautics, United States Air Force Academy, Springs, Colorado, CO, United States of America
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Harvey C. Joint extension speed dictates bio-inspired morphing trajectories for optimal longitudinal flight dynamics. J R Soc Interface 2024; 21:20230734. [PMID: 38654630 PMCID: PMC11040252 DOI: 10.1098/rsif.2023.0734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 02/05/2024] [Accepted: 03/11/2024] [Indexed: 04/26/2024] Open
Abstract
Avian wing morphing allows dynamic, active control of complex flight manoeuvres. Previous linear time-invariant (LTI) models have quantified the effect of varying fixed wing configurations but the time-dependent effects of morphing between different configurations is not well understood. To fill this gap, I implemented a linear parameter-varying (LPV) model for morphing wing gull flight. This approach models the wing joint angles as scheduled parameters and accounts for nonlinear kinematic and gravitational effects while interpolating between LTI models at discrete trim points. With the resulting model, I investigated the longitudinal response associated with various joint extension trajectories. By optimizing the extension trajectory for four independent objectives (speed and pitch angle overshoot, speed rise time and pitch angle settling time), I found that the extension trajectory inherent to the gull wing does not guarantee an optimal response but may provide a sufficient response with a simpler mechanical implementation. Furthermore, the results indicated that gulls likely require extension speed feedback. This morphing LPV model provides insights into underlying control mechanisms, which may allow for avian-like flight in future highly manoeuvrable uncrewed aerial vehicles.
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Affiliation(s)
- C. Harvey
- Department of Mechanical and Aerospace Engineering, University of California, Davis, CA95616, USA
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Rader JA, Hedrick TL. Morphological evolution of bird wings follows a mechanical sensitivity gradient determined by the aerodynamics of flapping flight. Nat Commun 2023; 14:7494. [PMID: 37980422 PMCID: PMC10657351 DOI: 10.1038/s41467-023-43108-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 10/31/2023] [Indexed: 11/20/2023] Open
Abstract
The physical principles that govern the function of biological structures also mediate their evolution, but the evolutionary drivers of morphological traits within complex structures can be difficult to predict. Here, we use morphological traits measured from 1096 3-dimensional bird wing scans from 178 species to test the interaction of two frameworks for relating morphology to evolution. We examine whether the evolutionary rate (σ2) and mode is dominated by the modular organization of the wing into handwing and armwing regions, and/or the relationship between trait morphology and functional output (i.e. mechanical sensitivity, driven here by flapping flight aerodynamics). Our results support discretization of the armwing and handwing as morphological modules, but morphological disparity and σ2 varied continuously with the mechanical sensitivity gradient and were not modular. Thus, mechanical sensitivity should be considered an independent and fundamental driver of evolutionary dynamics in biomechanical traits, distinct from morphological modularity.
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Affiliation(s)
- Jonathan A Rader
- Dept. of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
| | - Tyson L Hedrick
- Dept. of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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Saussaman T, Nafi A, Charland D, Ben-Gida H, Gurka R. The role of leading-edge serrations in controlling the flow over owls' wing. BIOINSPIRATION & BIOMIMETICS 2023; 18:066001. [PMID: 37650253 DOI: 10.1088/1748-3190/acf540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 08/30/2023] [Indexed: 09/01/2023]
Abstract
We studied the effects of leading-edge serrations on the flow dynamics developed over an owl wing model. Owls are predatory birds. Most owl species are nocturnal, with some active during the day. The nocturnal ones feature stealth capabilities that are partially attributed to their wing microfeatures. One of these microfeatures is small rigid combs (i.e. serrations) aligned at an angle with respect to the incoming flow located at the wings' leading-edge region of the primaries. These serrations are essentially passive flow control devices that enhance some of the owls' flight characteristics, such as aeroacoustics and, potentially, aerodynamics. We performed a comparative study between serrated and non-serrated owl wing models and investigated how the boundary layer over these wings changes in the presence of serrations over a range of angles of attack. Using particle image velocimetry, we measured the mean and turbulent flow characteristics and analyzed the flow patterns within the boundary layer region. Our experimental study suggests that leading-edge serrations modify the boundary layer over the wing at all angles of attack, but not in a similar manner. At low angles of attack (<20°), the serrations amplified the turbulence activity over the wing planform without causing any significant change in the mean flow. At 20° angle of attack, the serrations act to suppress existing turbulence conditions, presumably by causing an earlier separation closer to the leading-edge region, thus enabling the flow to reattach prior to shedding downstream into the wake. Following the pressure Hessian equation, turbulence suppression reduces the pressure fluctuations gradients. This reduction over the wing would weaken, to some extent, the scattering of aerodynamic noise in the near wake region.
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Affiliation(s)
- Tanner Saussaman
- Physics and Engineering Science, Coastal Carolina University, Conway, SC, United States of America
| | - Asif Nafi
- Physics and Engineering Science, Coastal Carolina University, Conway, SC, United States of America
| | - David Charland
- Mechanical and Aerospace Engineering, George Washington University, Washington, DC, United States of America
| | - Hadar Ben-Gida
- Institute for Aerospace Studies, University of Toronto, Toronto, ON, Canada
| | - Roi Gurka
- Physics and Engineering Science, Coastal Carolina University, Conway, SC, United States of America
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A Comparison of Aerodynamic Parameters in Two Subspecies of the American Barn Owl (Tyto furcata). Animals (Basel) 2022; 12:ani12192532. [PMID: 36230274 PMCID: PMC9558544 DOI: 10.3390/ani12192532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 09/18/2022] [Accepted: 09/19/2022] [Indexed: 11/16/2022] Open
Abstract
Simple Summary Morphology and function depend on the ecological niche in which an animal lives. Barn owls, occurring on all continents, occupy a nocturnal niche. These birds prey mainly on small rodents but include other small vertebrates and invertebrates in the diet. The size of the barn-owl species and subspecies varies considerably. The American continent harbors the species Tyto furcata. The body mass of the subspecies in North America (T.f.pratincola) is about a factor of two higher than that of the subspecies living on the Galapagos archipelago (T.f.puncatissima). We asked how this difference translates into aerodynamic parameters. The key question was whether there is so-called similarity scaling or not. In other words, whether important aerodynamic parameters scale according to body mass. This is called isometric scaling. Deviation from isometric scaling is called allometric scaling. If we use the subspecies from the continent as a reference, we find that the Galapagos barn owl has relatively larger wings than expected from isometric scaling. This translates into a lower wing loading in punctatissima than in pratincola. A lower wing loading means higher maneuverability. We speculate that the higher maneuverability allows the Galapagos owl to catch smaller prey, especially insects. Abstract Aerodynamic parameters, such as wing loading, are important indicators of flight maneuverability. We studied two subspecies of the American Barn owl (Tyto furcata), the North American subspecies, T.f.pratincola, and the Galapagos subspecies, T.f.punctatissima, with respect to aerodynamic parameters and compared our findings with those in other owl and bird species. The body mass of T.f.pratincola is about two times higher than that of T.f.punctatissima. Wing loading between the two subspecies scales allometrically. Wing loading in T.f.pratincola is about 50% higher than in T.f.punctatissima. The scaling of wing length is not statistically different from the prediction for isometric scaling. By contrast, the wing chord in T.f.punctatissima is larger than predicted by isometric scaling, as is the wing area. The scaling of wing loading observed here for T.f.punctatissima differs considerably from the scaling in other owl and bird species as available in the literature. We speculate that the allometric scaling helps T.f.punctatissima to catch smaller prey such, as insects that are found in many pellets of T.f.punctatissima, despite the fact that in both subspecies, small rodents make up most of the diet.
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Cheney JA, Rehm JC, Swartz SM, Breuer KS. Bats actively modulate membrane compliance to control camber and reduce drag. J Exp Biol 2022; 225:275993. [PMID: 35762250 PMCID: PMC9377553 DOI: 10.1242/jeb.243974] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 06/22/2022] [Indexed: 11/23/2022]
Abstract
Bat wing skin is exceptionally compliant and cambers significantly during flight. Plagiopatagiales proprii, arrays of small muscles embedded in the armwing membrane, are activated during flight and are hypothesized to modulate membrane tension. We examined the function of these muscles using Jamaican fruit bats, Artibeus jamaicensis. When these muscles were paralyzed using botulinum toxin, the bats preferred flight speed decreased and they were unable to fly at very low speeds. Paralysis of the plagiopatagiales also resulted in increased armwing camber consistent with a hypothesized role of modulating aeroelastic interactions. Other compensatory kinematics included increased downstroke angle and increased wingbeat amplitude. These results are consistent with the bats experiencing increased drag and flight power costs associated with the loss of wing-membrane control. Our results indicate that A. jamaicensis likely always employ their wing membrane muscles during sustained flight to control camber and to enhance flight efficiency over a wide flight envelope. Highlighted Article: Temporary paralysis of wing-skin-embedded muscles in bats significantly increases wing-membrane camber, reduces preferred flight speed and prevents very slow flight, highlighting their role in control, efficiency and expanding the flight envelope.
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Affiliation(s)
- Jorn A Cheney
- Royal Veterinary College, London NW1 0TU, UK.,Dept. of Ecology and Evolutionary Biology, Brown University, Providence 02912, USA
| | - Jeremy C Rehm
- Dept. of Ecology and Evolutionary Biology, Brown University, Providence 02912, USA
| | - Sharon M Swartz
- Dept. of Ecology and Evolutionary Biology, Brown University, Providence 02912, USA.,School of Engineering, Brown University, Providence 02912, USA
| | - Kenneth S Breuer
- Dept. of Ecology and Evolutionary Biology, Brown University, Providence 02912, USA.,School of Engineering, Brown University, Providence 02912, USA
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Harvey C, Baliga VB, Wong JCM, Altshuler DL, Inman DJ. Birds can transition between stable and unstable states via wing morphing. Nature 2022; 603:648-653. [PMID: 35264798 PMCID: PMC8942853 DOI: 10.1038/s41586-022-04477-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 01/26/2022] [Indexed: 11/12/2022]
Abstract
Birds morph their wing shape to accomplish extraordinary manoeuvres1–4, which are governed by avian-specific equations of motion. Solving these equations requires information about a bird’s aerodynamic and inertial characteristics5. Avian flight research to date has focused on resolving aerodynamic features, whereas inertial properties including centre of gravity and moment of inertia are seldom addressed. Here we use an analytical method to determine the inertial characteristics of 22 species across the full range of elbow and wrist flexion and extension. We find that wing morphing allows birds to substantially change their roll and yaw inertia but has a minimal effect on the position of the centre of gravity. With the addition of inertial characteristics, we derived a novel metric of pitch agility and estimated the static pitch stability, revealing that the agility and static margin ranges are reduced as body mass increases. These results provide quantitative evidence that evolution selects for both stable and unstable flight, in contrast to the prevailing narrative that birds are evolving away from stability6. This comprehensive analysis of avian inertial characteristics provides the key features required to establish a theoretical model of avian manoeuvrability. Analysis of inertial characteristics across 22 bird species shows that evolution has selected for avian manoeuvrability using both stable and unstable flight dynamics.
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Affiliation(s)
- C Harvey
- Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI, USA.
| | - V B Baliga
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - J C M Wong
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - D L Altshuler
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - D J Inman
- Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI, USA
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Song J, Cheney JA, Bomphrey RJ, Usherwood JR. Virtual manipulation of tail postures of a gliding barn owl ( Tyto alba) demonstrates drag minimization when gliding. J R Soc Interface 2022; 19:20210710. [PMID: 35135296 PMCID: PMC8833102 DOI: 10.1098/rsif.2021.0710] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Aerodynamic functions of the avian tail have been studied previously using observations of bird flight, physical models in wind tunnels, theoretical modelling and flow visualization. However, none of these approaches has provided rigorous, quantitative evidence concerning tail functions because (i) appropriate manipulation and controls cannot be achieved using live animals and (ii) the aerodynamic interplay between the wings and body challenges reductive theoretical or physical modelling approaches. Here, we have developed a comprehensive analytical drag model, calibrated by high-fidelity computational fluid dynamics (CFD), and used it to investigate the aerodynamic action of the tail by virtually manipulating its posture. The bird geometry used for CFD was reconstructed previously using stereo-photogrammetry of a freely gliding barn owl (Tyto alba) and we validated the CFD simulations against wake measurements. Using this CFD-calibrated drag model, we predicted the drag production for 16 gliding flights with a range of tail postures. These observed postures are set in the context of a wider parameter sweep of theoretical postures, where the tail spread and elevation angles were manipulated independently. The observed postures of our gliding bird corresponded to near minimal total drag.
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Affiliation(s)
- Jialei Song
- School of Mechanical Engineering, Dongguan University of Technology, Dongguan, Guangdong, People's Republic of China
- Structure and Motion Laboratory, Royal Veterinary College, North Mymms, Hatfield, UK
| | - Jorn A. Cheney
- Structure and Motion Laboratory, Royal Veterinary College, North Mymms, Hatfield, UK
| | - Richard J. Bomphrey
- Structure and Motion Laboratory, Royal Veterinary College, North Mymms, Hatfield, UK
| | - James R. Usherwood
- Structure and Motion Laboratory, Royal Veterinary College, North Mymms, Hatfield, UK
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