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Skulborstad A, Goulbourne NC. A chemo-mechanical constitutive model for muscle activation in bat wing skins. J R Soc Interface 2024; 21:20230593. [PMID: 38981517 DOI: 10.1098/rsif.2023.0593] [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: 10/11/2023] [Accepted: 04/17/2024] [Indexed: 07/11/2024] Open
Abstract
Birds, bats and insects have evolved unique wing structures to achieve a wide range of flight capabilities. Insects have relatively stiff and passive wings, birds have a complex and hierarchical feathered structure and bats have an articulated skeletal system integrated with a highly stretchable skin. The compliant skin of the wing distinguishes bats from all other flying animals and contributes to bats' remarkable, highly manoeuvrable flight performance and high energetic efficiency. The structural and functional complexity of the bat wing skin is one of the least understood although important elements of the bat flight anatomy. The wing skin has two unusual features: a discrete array of very soft elastin fibres and a discrete array of skeletal muscle fibres. The latter is intriguing because skeletal muscle is typically attached to bone, so the arrangement of intramembranous muscle in soft skin raises questions about its role in flight. In this paper, we develop a multi-scale chemo-mechanical constitutive model for bat wing skin. The chemo-mechanical model links cross-bridge cycling to a structure-based continuum model that describes the active viscoelastic behaviour of the soft anisotropic skin tissue. Continuum models at the tissue length-scale are valuable as they are easily implemented in commercial finite element codes to solve problems involving complex geometries, loading and boundary conditions. The constitutive model presented in this paper will be used in detailed finite element simulations to improve our understanding of the mechanics of bat flight in the context of wing kinematics and aerodynamic performance.
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Affiliation(s)
| | - N C Goulbourne
- Aerospace Engineering, University of Michigan, Ann Arbor, MI, USA
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2
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Håkansson J, Quinn BL, Shultz AL, Swartz SM, Corcoran AJ. Application of a novel deep learning-based 3D videography workflow to bat flight. Ann N Y Acad Sci 2024; 1536:92-106. [PMID: 38652595 DOI: 10.1111/nyas.15143] [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] [Indexed: 04/25/2024]
Abstract
Studying the detailed biomechanics of flying animals requires accurate three-dimensional coordinates for key anatomical landmarks. Traditionally, this relies on manually digitizing animal videos, a labor-intensive task that scales poorly with increasing framerates and numbers of cameras. Here, we present a workflow that combines deep learning-powered automatic digitization with filtering and correction of mislabeled points using quality metrics from deep learning and 3D reconstruction. We tested our workflow using a particularly challenging scenario: bat flight. First, we documented four bats flying steadily in a 2 m3 wind tunnel test section. Wing kinematic parameters resulting from manually digitizing bats with markers applied to anatomical landmarks were not significantly different from those resulting from applying our workflow to the same bats without markers for five out of six parameters. Second, we compared coordinates from manual digitization against those yielded via our workflow for bats flying freely in a 344 m3 enclosure. Average distance between coordinates from our workflow and those from manual digitization was less than a millimeter larger than the average human-to-human coordinate distance. The improved efficiency of our workflow has the potential to increase the scalability of studies on animal flight biomechanics.
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Affiliation(s)
- Jonas Håkansson
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, Colorado, USA
| | - Brooke L Quinn
- Department of Ecology, Evolution, and Organismal Biology, Brown University, Providence, Rhode Island, USA
| | - Abigail L Shultz
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, Colorado, USA
| | - Sharon M Swartz
- Department of Ecology, Evolution, and Organismal Biology, Brown University, Providence, Rhode Island, USA
- School of Engineering, Brown University, Providence, Rhode Island, USA
| | - Aaron J Corcoran
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, Colorado, USA
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3
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Lilong C, Yu Y. Maneuvering Characteristics of Bilateral Amplitude-Asymmetric Flapping Motion Based on a Bat-Inspired Flexible Wing. Biomimetics (Basel) 2024; 9:148. [PMID: 38534833 DOI: 10.3390/biomimetics9030148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 02/19/2024] [Accepted: 02/27/2024] [Indexed: 03/28/2024] Open
Abstract
Flapping-wing micro air vehicles (FWMAVs) have gained much attention from researchers due to their exceptional performance at low Reynolds numbers. However, the limited understanding of active aerodynamic modulation in flying creatures has hindered their maneuverability from reaching that of their biological counterparts. In this article, experimental investigations were conducted to examine the effect of the bilateral amplitude asymmetry of flexible flapping wings. A reduced bionic model featuring bat-like wings is built, and a dimensionless number ΔΦ* is introduced to scale the degree of bilateral amplitude asymmetry in flapping motion. The experimental results suggest that the bilateral amplitude-asymmetric flapping motion primarily induces maneuvering control forces of coupling roll moment and yaw moment. Also, roll moment and yaw moment have a good linear relationship. To achieve more efficient maneuvers based on this asymmetric motion, it is advisable to maintain ΔΦ* within the range of 0 to 0.4. The magnitude of passive pitching deformation during the downstroke is significantly greater than that during the upstroke. The phase of the peak of the passive pitching angle advances with the increase in flapping amplitude, while the valleys lag. And the proportion of pronation and supination in passive pitching motion cannot be adjusted by changing the flapping amplitude. These findings have important practical relevance for regulating turning maneuvers based on amplitude asymmetry and help to understand the active aerodynamic modulation mechanism through asymmetric wing kinematics.
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Affiliation(s)
- Chuyi Lilong
- Laboratory for Biomechanics of Animal Locomotion, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yongliang Yu
- Laboratory for Biomechanics of Animal Locomotion, University of Chinese Academy of Sciences, Beijing 100049, China
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Lauber M, Weymouth GD, Limbert G. Rapid flapping and fibre-reinforced membrane wings are key to high-performance bat flight. J R Soc Interface 2023; 20:20230466. [PMID: 37963557 PMCID: PMC10645508 DOI: 10.1098/rsif.2023.0466] [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: 08/09/2023] [Accepted: 10/20/2023] [Indexed: 11/16/2023] Open
Abstract
Bats fly using significantly different wing motions from other fliers, stemming from the complex interplay of their membrane wings' motion and structural properties. Biological studies show that many bats fly at Strouhal numbers, the ratio of flapping to flight speed, 50-150% above the range typically associated with optimal locomotion. We use high-resolution fluid-structure interaction simulations of a bat wing to independently study the role of kinematics and material/structural properties in aerodynamic performance and show that peak propulsive and lift efficiencies for a bat-like wing motion require flapping 66% faster than for a symmetric motion, agreeing with the increased flapping frequency observed in zoological studies. In addition, we find that reduced membrane stiffness is associated with improved propulsive efficiency until the membrane flutters, but that incorporating microstructural anisotropy arising from biological fibre reinforcement enables a tenfold reduction of the flutter energy while maintaining high aerodynamic efficiency. Our results indicate that animals with specialized flapping motions may have correspondingly specialized flapping speeds, in contrast to arguments for a universally efficient Strouhal range. Additionally, our study demonstrates the significant role that the microstructural constitutive properties of the membrane wing of a bat can have in its propulsive performance.
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Affiliation(s)
- Marin Lauber
- Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK
- Faculty of Mechanical Maritime and Materials Engineering (3mE), Delft University of Technology, Delft, The Netherlands
| | - Gabriel D. Weymouth
- Faculty of Mechanical Maritime and Materials Engineering (3mE), Delft University of Technology, Delft, The Netherlands
| | - Georges Limbert
- Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK
- Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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Zhang J, Zhao N, Qu F. Bio-inspired flapping wing robots with foldable or deformable wings: a review. BIOINSPIRATION & BIOMIMETICS 2022; 18:011002. [PMID: 36317380 DOI: 10.1088/1748-3190/ac9ef5] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Accepted: 10/31/2022] [Indexed: 06/16/2023]
Abstract
Traditional flapping-wing robots (FWRs) obtain lift and thrust by relying on the passive deformation of their wings which cannot actively fold or deform. In contrast, flying creatures such as birds, bats, and insects can maneuver agilely through active folding or deforming their wings. Researchers have developed many bio-inspired foldable or deformable wings (FDWs) imitating the wings of flying creatures. The foldable wings refer to the wings like the creatures' wings that can fold in an orderly manner close to their bodies. Such wings have scattered feathers or distinct creases that can be stacked and folded to reduce the body envelope, which in nature is beneficial for these animals to prevent wing damage and ensure agility in crossing bushes. The deformable wings refer to the active deformation of the wings using active driving mechanisms and the passive deformation under the aerodynamic force, which functionally imitates the excellent hydrodynamic performance of the deformable body and wings of the creatures. However, the shape and external profile changes of deformable wings tend to be much smaller than that of folding wings. FDWs enable the FWRs to improve flight degree of flexibility, maneuverability, and efficiency and reduce flight energy consumption. However, FDWs still need to be studied, and a comprehensive review of the state-of-the-art progress of FDWs in FWR design is lacking. This paper analyzes the wing folding and deformation mechanisms of the creatures and reviews the latest progress of FWRs with FDWs. Furthermore, we summarize the current limitations and propose future directions in FDW design, which could help researchers to develop better FWRs for safe maneuvering in obstacle-dense environments.
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Affiliation(s)
- Jun Zhang
- The State Key Laboratory of Bioelectronics, School of Instrument Science and Engineering, Southeast University, Nanjing 210096, People's Republic of China
| | - Ning Zhao
- The State Key Laboratory of Bioelectronics, School of Instrument Science and Engineering, Southeast University, Nanjing 210096, People's Republic of China
| | - Feiyang Qu
- The State Key Laboratory of Bioelectronics, School of Instrument Science and Engineering, Southeast University, Nanjing 210096, People's Republic of China
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Fan X, Swartz S, Breuer K. Power requirements for bat-inspired flapping flight with heavy, highly articulated and cambered wings. J R Soc Interface 2022; 19:20220315. [PMID: 36128710 PMCID: PMC9490335 DOI: 10.1098/rsif.2022.0315] [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: 04/22/2022] [Accepted: 08/25/2022] [Indexed: 11/12/2022] Open
Abstract
Bats fly with highly articulated and heavy wings. To understand their power requirements, we develop a three-dimensional reduced-order model, and apply it to flights of Cynopterus brachyotis, the lesser dog-faced fruit bat. Using previously measured wing kinematics, the model computes aerodynamic forces using blade element momentum theory, and incorporates inertial forces of the flapping wing using the measured mass distribution of the membrane wing and body. The two are combined into a Lagrangian equation of motion, and we performed Monte Carlo simulations to address uncertainties in measurement errors and modelling assumptions. We find that the camber of the armwing decreases with flight speed whereas the handwing camber is more independent of speed. Wing camber disproportionately impacts energetics, mainly during the downstroke, and increases the power requirement from 8% to 22% over flight speed U = 3.2-7.4 m s-1. We separate total power into aerodynamic and inertial components, and aerodynamic power into parasitic, profile and induced power, and find strong agreement with previous theoretical and experimental studies. We find that inertia of wings help to balance aerodynamic forces, alleviating the muscle power required for weight support and thrust generation. Furthermore, the model suggests aerodynamic forces assist in lifting the heavy wing during upstroke.
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Affiliation(s)
- Xiaozhou Fan
- Center for Fluid Mechanics, School of Engineering, Brown University, Providence, RI, USA
| | - Sharon Swartz
- Center for Fluid Mechanics, School of Engineering, Brown University, Providence, RI, USA
- Department of Ecology, Evolution, and Organismal Biology, Aeromechanics & Evolutionary Morphology Lab, Brown University, Providence, RI, USA
| | - Kenneth Breuer
- Center for Fluid Mechanics, School of Engineering, Brown University, Providence, RI, USA
- Department of Ecology, Evolution, and Organismal Biology, Aeromechanics & Evolutionary Morphology Lab, Brown University, Providence, RI, USA
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7
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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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9
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Singh SK, Zhang LB, Zhao JS. Reconstruction of Flight Parameters of a Bat for Flapping Robots. J Biomech Eng 2021; 144:1122983. [PMID: 34729585 DOI: 10.1115/1.4052889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Indexed: 11/08/2022]
Abstract
The flight of bats is comparatively less documented and understood than birds and insects and may provide novel inspiration for the design of flapping flight robots. This study captured the natural flight of short-nosed fruit bats (Cynopterus sphinx) by an optical motion capture system, 'OptiTrack', with pasted markers on the wings and body to reconstruct the flight parameters. Due to the self-occlusion at some moments, points on the membrane wings cannot be captured by any cameras. To draw a smooth trajectory, it is desired to reconstruct all missing data. Therefore, an algorithm is proposed by using numerical techniques, accompanied by modern mathematical and computational tools, to envisage the missing data from the captured flight. The least-square fitted polynomial engendered the parameter equations for x-, y- and z-coordinates of marked points which were used to reconstruct the trajectory of the flight. The parameter equations of position coordinates were also used to compute the morphological and aerodynamic characteristics of the flight. The most outstanding contribution of the work is that not only the trajectory, velocity and velocity field but also the morphing areas of the membrane wings were recreated using the reconstructed data. These data and reconstructed curves of trajectory and velocity field will be used for the further aerodynamic analysis and mechanism design of the flapping robot. This method can also be generalized to reconstruct the performance parameters of any other animals for bionic design.
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Affiliation(s)
- Sudeep Kumar Singh
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China; Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Li-Biao Zhang
- Guangdong Key Laboratory of Animal Conservation and Resource Utilization, Guangdong Public Laboratory of Wild Animal Conservation and Utilization, Institute of Zoology, Guangdong Academy of Sciences, Guangzhou 510260, China
| | - Jing-Shan Zhao
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China; Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
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Zurman-Nasution AN, Ganapathisubramani B, Weymouth GD. Fin sweep angle does not determine flapping propulsive performance. J R Soc Interface 2021; 18:20210174. [PMID: 34034533 PMCID: PMC8157821 DOI: 10.1098/rsif.2021.0174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 05/04/2021] [Indexed: 12/04/2022] Open
Abstract
The importance of the leading-edge sweep angle of propulsive surfaces used by unsteady swimming and flying animals has been an issue of debate for many years, spurring studies in biology, engineering, and robotics with mixed conclusions. In this work, we provide results from three-dimensional simulations on single-planform finite foils undergoing tail-like (pitch-heave) and flipper-like (twist-roll) kinematics for a range of sweep angles covering a substantial portion of animals while carefully controlling all other parameters. Our primary finding is the negligible 0.043 maximum correlation between the sweep angle and the propulsive force and power for both tail-like and flipper-like motions. This indicates that fish tails and mammal flukes with similar range and size can have a large range of potential sweep angles without significant negative propulsive impact. Although there is a slight benefit to avoiding large sweep angles, this is easily compensated by adjusting the fin's motion parameters such as flapping frequency, amplitude and maximum angle of attack to gain higher thrust and efficiency.
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Affiliation(s)
- Andhini N. Zurman-Nasution
- Faculty of Engineering and Physical Sciences, University of Southampton, Southampton Boldrewood Innovation Campus, UK
| | - Bharathram Ganapathisubramani
- Faculty of Engineering and Physical Sciences, University of Southampton, Southampton Boldrewood Innovation Campus, UK
| | - Gabriel D. Weymouth
- Faculty of Engineering and Physical Sciences, University of Southampton, Southampton Boldrewood Innovation Campus, UK
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Singh SK, Zhang LB, Zhao JS. Direct Measurements of the Wing Kinematics of a Bat in Straight Flight. J Biomech Eng 2021; 143:041006. [PMID: 33210129 DOI: 10.1115/1.4049161] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Indexed: 11/08/2022]
Abstract
Bat is the only mammal in the nature that can fly. Compared with birds and insects, bats are quite special in that their wings are formed by an elastic membrane, which renders that the airfoil deforms greatly during downstroke and upstroke. Due to the compliant skin of a bat, the movements of its wings are three-dimensionally complex during diverse flight behaviors. To understand the maneuverability and flight performance, three-dimensional reconstruction of the flight kinematics is essential. This study focuses on the reconstruction of the wing kinematics of the bat and identifies the primary relationship of parameters of aerodynamics in straight flight. With markers pasted on the wings and body of a bat, the motions of these points are recorded by a computerized optical motion capture system. The kinematic analysis shows that the motion of wings is very intricate. The digits of the wing display the sign of coupled motion. A novel approach was developed to measure the angle of attack and flapping angle of the wing. The angle of attack of leading edge differs with the overall angle of attack of the wing. The kinematics of the bat's wing is helpful to interpret the secret of the bat's flight.
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Affiliation(s)
- Sudeep Kumar Singh
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China; Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
| | - Li-Biao Zhang
- Guangdong Key Laboratory of Animal Conservation and Resource Utilization, Guangdong Public Laboratory of Wild Animal Conservation and Utilization, Institute of Zoology, Guangdong Academy of Sciences, Guangzhou 510260, China
| | - Jing-Shan Zhao
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China; Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
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Luziga C, Miyata H, Nagahisa H, Oji T, Wada N. Muscle fibre distribution in forelimb, hindlimb and trunk muscles in three bat species: The little Japanese horseshoe, greater horseshoe and Egyptian fruit. Anat Histol Embryol 2021; 50:685-693. [PMID: 33783854 DOI: 10.1111/ahe.12670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 02/02/2021] [Accepted: 03/08/2021] [Indexed: 11/30/2022]
Abstract
This study characterised muscle fibres in trunk, forelimb and hindlimb muscles of three bat species: little Japanese horseshoe (Rhinolophus cornutus), greater horseshoe (Rhinolophus ferrumequinum) and Egyptian fruit (Rousettus aegyptiacus). Twenty-seven muscles from trunk, forelimb and hindlimb were dissected, weighed and analysed by immunohistochemistry and sodium didecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and determined their cross-sectional areas (CSA). Results showed that Type IIa and Type IIa/x made the highest proportion of total muscle mass. Moderate proportion was formed by Type IIb. Type I and IIx appeared at very low levels in all bats. Type IIb was the only fibre type detected in patagial muscles in wing membrane of greater horseshoe while other fibre types were not observed. Type I muscle fibres were very few and appeared infrequently in fifteen muscles of Egyptian fruit and in only one muscle in each, greater horseshoe and little Japanese horseshoe. Type IIx was also detected in three muscles in greater horseshoe and only one muscle in Egyptian fruit but none in little Japanese horseshoe. The highest average CSA μm2 was detected in Type IIb and values were 734.2μm2 for LHB; 1537.9μm2 for GHB and 1,720.9μm2 for EFB. Lowest and undetermined values were observed for Type I and IIx. These data demonstrate that Type IIa, IIa/x and IIb form significant proportion of adult bat muscle mass and Type IIb is the largest fibre type. The distribution pattern is suggestive of specialised functions of the fibres in relation to orientation and speed of bats during flight.
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Affiliation(s)
- Claudius Luziga
- Department of Veterinary Anatomy and Pathology, College of Veterinary Medicine and Biomedical Sciences, Sokoine University of Agriculture, Morogoro, Tanzania
| | - Hirofumi Miyata
- Biological Sciences, Graduate School of Sciences and Technology for Innovation, Yamaguchi, Japan
| | - Hiroshi Nagahisa
- Biological Sciences, Graduate School of Sciences and Technology for Innovation, Yamaguchi, Japan
| | - Takashi Oji
- The United Veterinary Graduated School, Yamaguchi University, Yamaguchi, Japan
| | - Naomi Wada
- Department of System Physiology, Yamaguchi University, Yamaguchi, Japan
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Abstract
There are at least eight ways that wings potentially produce sound. Five mechanisms are aerodynamic sounds, created by airflow, and three are structural sound created by interactions of solid surfaces. Animal flight is low Mach (M), meaning all animals move at <30% of the speed of sound. Thus in aerodynamic mechanisms the effects of air compressibility can be ignored, except in mechanism #1. Mechanism #1 is trapped air, in which air approaches or exceeds Mach 1 as it escapes a constriction. This mechanism is hypothetical but likely. #2 is Gutin sound, the aerodynamic reaction to lift and drag. This mechanism is ubiquitous in flight, and generates low frequency sound such as the humming of hummingbirds or insect wing tones. #3 is turbulence-generated atonal whooshing sounds, which are also widespread in animal flight. #4 are whistles, tonal sounds generated by geometry-induced flow feedback. This mechanism is hypothetical. #5 is aeroelastic flutter, sound generated by elasticity-induced feedback that is usually but not always tonal. This is widespread in birds (feathers are predisposed to flutter) but apparently not bats or insects. Mechanism #6 is rubbing sound (including stridulation), created when bird feathers or insect wings slide past each other. Atonal rubbing sounds are widespread in bird flight and insects; tonal stridulation is widespread in insects. #7 is percussion, created when two stiff elements collide and vibrate, and is present in some birds and insects. Mechanism #8 are tymbals and other bistable conformations. These are stiff elements that snap back and forth between two conformations, producing impulsive, atonal sound. Tymbals are widespread in insects but not birds or bats; insect cuticle appears predisposed to form tymbals. There are few examples of bat wing sounds: are bats intrinsically quiet, or just under-studied? These mechanisms, especially Gutin sound, whooshes, and rubbing (#2, #3, and #6) are prominent cues in ordinary flight of all flying animals, and are the "acoustic substrate" available to be converted from an adventitious sound (cue) into a communication signal. For instance, wing sounds have many times evolved into signals that are incorporated into courtship displays. Conversely, these are the sounds selected to be suppressed if quiet flight is selected for. The physical mechanisms that underlie animal sounds provide context for understanding the ways in which signals and cues may evolve.
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Affiliation(s)
- Christopher J Clark
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, CA 92521, USA
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Cao T, Jin JP. Evolution of Flight Muscle Contractility and Energetic Efficiency. Front Physiol 2020; 11:1038. [PMID: 33162892 PMCID: PMC7581897 DOI: 10.3389/fphys.2020.01038] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Accepted: 07/29/2020] [Indexed: 12/19/2022] Open
Abstract
The powered flight of animals requires efficient and sustainable contractions of the wing muscles of various flying species. Despite their high degree of phylogenetic divergence, flight muscles in insects and vertebrates are striated muscles with similarly specialized sarcomeric structure and basic mechanisms of contraction and relaxation. Comparative studies examining flight muscles together with other striated muscles can provide valuable insights into the fundamental mechanisms of muscle contraction and energetic efficiency. Here, we conducted a literature review and data mining to investigate the independent emergence and evolution of flight muscles in insects, birds, and bats, and the likely molecular basis of their contractile features and energetic efficiency. Bird and bat flight muscles have different metabolic rates that reflect differences in energetic efficiencies while having similar contractile machinery that is under the selection of similar natural environments. The significantly lower efficiency of insect flight muscles along with minimized energy expenditure in Ca2+ handling is discussed as a potential mechanism to increase the efficiency of mammalian striated muscles. A better understanding of the molecular evolution of myofilament proteins in the context of physiological functions of invertebrate and vertebrate flight muscles can help explore novel approaches to enhance the performance and efficiency of skeletal and cardiac muscles for the improvement of human health.
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Affiliation(s)
| | - J.-P. Jin
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, United States
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15
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Windes P, Tafti DK, Müller R. Determination of spatial fidelity required to accurately mimic the flight dynamics of a bat. BIOINSPIRATION & BIOMIMETICS 2019; 14:066011. [PMID: 31443100 DOI: 10.1088/1748-3190/ab3e2a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Bats possess unique flight capabilities enabled by their wing morphology. While the articulated bone structure and flexible membrane constituting the wing are known to play a critical role in aerodynamic performance, the relationship has never been robustly quantified. Characterization of the sensitivity between precise wing contour and aerodynamic performance is important when designing a biomimetic flight vehicle based on experimentally measured wing kinematics. 3D optical motion capture, a standard method for obtaining wing kinematic measurements, discretely samples the smooth surface of a bat wing during flight. If the constellation of tracked 3D points is too sparse, a loss of critical information occurs. Here, we have explored the relationship between the density of wing surface points and several aerodynamic metrics, specifically, wing surface area variation, aerodynamic loads, and power expenditure. Loads and power were calculated using an incompressible Navier-Stokes solver. Of the metrics examined, aerodynamic power was found to be most sensitive to the spatial fidelity of the wing-the normalized root mean squared difference (NRMSD) between the 10- and 238-point cases was 35%. Load calculations varied slightly less with a peak NRMSD of 24% between the highest and lowest fidelity cases. Lastly, the wing surface area was least sensitive to the spatial fidelity of the wing kinematics, with a maximum NRMSD surface area of 8%. Close similarity in aerodynamic behavior was observed when using either a 120- and 238-point surface representation, establishing a bound to the sensitivity between wing shape and aerodynamics. The results from the 10- and 22-point configurations demonstrate that sparse representation of a wing surface can lead to a loss of information. The characterization of kinematic complexity of the wings both informs how many degrees of freedom are important to measure and also informs how many degrees of freedom are required to robotically reproduce the flapping flight.
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Affiliation(s)
- Peter Windes
- Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA, United States of America
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16
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Vejdani HR, Boerma DB, Swartz SM, Breuer KS. The dynamics of hovering flight in hummingbirds, insects and bats with implications for aerial robotics. BIOINSPIRATION & BIOMIMETICS 2018; 14:016003. [PMID: 30411710 DOI: 10.1088/1748-3190/aaea56] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We analyze the effects of morphology and wing kinematics on the performance of hovering flight. We present a simplified dynamical model with body translational and rotational degrees of freedom that incorporates the flapping, long-axis wing rotation and folding of the wing. To validate our simulation, we compare our results with direct measurements from hovering insects, hummingbirds and bats. Results show that long-axis wing rotation angle (a proxy for pronation) has a significant effect on energy efficiency. For a given wing rotation amplitude, the hovering system has a power-optimal flapping frequency for each stroke-plane orientation, and that frequency closely corresponds to the wingbeat frequencies observed in a diverse range of hummingbird species. We find that larger animals (with larger total mass and wing size), such as bats, require more power to maintain a stable hovering orbit and that hovering with a constant wingspan becomes increasingly impractical with increasing body size. We show, as an exemplar, that for a system of the size of a hovering bat, e.g. Glossophaga soricina, hovering with constant wingspan is dynamically possible, but is implausible and inefficient. For these conditions, hovering with varying wingspan, retracting the wing on the upstroke, is a more realistic hovering modality.
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Affiliation(s)
- Hamid R Vejdani
- School of Engineering, Brown University, Providence, RI, United States of America. Current Address: Mechanical Engineering Department, Lawrence Technological University, Southfield, MI, United States of America
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17
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Ortega-Jiménez VM, Combes SA. Living in a trash can: turbulent convective flows impair Drosophila flight performance. J R Soc Interface 2018; 15:rsif.2018.0636. [PMID: 30355810 DOI: 10.1098/rsif.2018.0636] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 10/01/2018] [Indexed: 11/12/2022] Open
Abstract
Turbulent flows associated with thermal convection are common in areas where the ground is heated by solar radiation, fermentation or other processes. However, it is unknown how these flow instabilities affect the locomotion of small insects, like fruit flies, that inhabit deserts and urban landscapes where surface temperatures can reach extreme values. We quantified flight performance of fruit flies (Drosophila melanogaster) traversing a chamber through still air and turbulent Rayleigh-Bénard convection cells produced by a vertical temperature gradient. A total of 34% of individuals were unable to reach the end of the chamber in convection, although peak flow speeds were modest relative to typical outdoor airflow. Individuals that were successful in convection were faster fliers and had larger wing areas than those that failed. All flies displayed higher pitch angles and lower mean flight speeds in convection. Successful individuals took longer to cross the chamber in convection, due to lower flight speeds and greater path sinuosity. All individuals displayed higher flapping frequencies in convection, and successful individuals also reduced stroke amplitude. Our results suggest that thermal convection poses a significant challenge for small fliers, resulting in increased travel times and energetic costs, or in some cases precluding insects from traversing these environments entirely.
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Affiliation(s)
| | - Stacey A Combes
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, CA, USA
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18
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Håkansson J, Jakobsen L, Hedenström A, Johansson LC. Body lift, drag and power are relatively higher in large-eared than in small-eared bat species. J R Soc Interface 2018; 14:rsif.2017.0455. [PMID: 29070593 DOI: 10.1098/rsif.2017.0455] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 09/26/2017] [Indexed: 11/12/2022] Open
Abstract
Bats navigate the dark using echolocation. Echolocation is enhanced by external ears, but external ears increase the projected frontal area and reduce the streamlining of the animal. External ears are thus expected to compromise flight efficiency, but research suggests that very large ears may mitigate the cost by producing aerodynamic lift. Here we compare quantitative aerodynamic measures of flight efficiency of two bat species, one large-eared (Plecotus auritus) and one small-eared (Glossophaga soricina), flying freely in a wind tunnel. We find that the body drag of both species is higher than previously assumed and that the large-eared species has a higher body drag coefficient, but also produces relatively more ear/body lift than the small-eared species, in line with prior studies on model bats. The measured aerodynamic power of P. auritus was higher than predicted from the aerodynamic model, while the small-eared species aligned with predictions. The relatively higher power of the large-eared species results in lower optimal flight speeds and our findings support the notion of a trade-off between the acoustic benefits of large external ears and aerodynamic performance. The result of this trade-off would be the eco-morphological correlation in bat flight, with large-eared bats generally adopting slow-flight feeding strategies.
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Affiliation(s)
- Jonas Håkansson
- Department of Biology, Lund University, Ecology Building, 223 62 Lund, Sweden
| | - Lasse Jakobsen
- Department of Biology, University of Southern Denmark, 5230 Odense, Denmark
| | - Anders Hedenström
- Department of Biology, Lund University, Ecology Building, 223 62 Lund, Sweden
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19
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Hubel TY, Hristov NI, Swartz SM, Breuer KS. Wake structure and kinematics in two insectivorous bats. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0385. [PMID: 27528775 DOI: 10.1098/rstb.2015.0385] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/11/2016] [Indexed: 11/12/2022] Open
Abstract
We compare kinematics and wake structure over a range of flight speeds (4.0-8.2 m s(-1)) for two bats that pursue insect prey aerially, Tadarida brasiliensis and Myotis velifer Body mass and wingspan are similar in these species, but M. velifer has broader wings and lower wing loading. By using high-speed videography and particle image velocimetry of steady flight in a wind tunnel, we show that three-dimensional kinematics and wake structure are similar in the two species at the higher speeds studied, but differ at lower speeds. At lower speeds, the two species show significant differences in mean angle of attack, body-wingtip distance and sweep angle. The distinct body vortex seen at low speed in T. brasiliensis and other bats studied to date is considerably weaker or absent in M. velifer We suggest that this could be influenced by morphology: (i) the narrower thorax in this species probably reduces the body-induced discontinuity in circulation between the two wings and (ii) the wing loading is lower, hence the lift coefficient required for weight support is lower. As a result, in M. velifer, there may be a decreased disruption in the lift generation between the body and the wing, and the strength of the characteristic root vortex is greatly diminished, both suggesting increased flight efficiency.This article is part of the themed issue 'Moving in a moving medium: new perspectives on flight'.
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Affiliation(s)
- Tatjana Y Hubel
- School of Engineering, Brown University, Providence, RI 02912, USA Structure and Motion Laboratory, Royal Veterinary College, Hatfield AL97TA, UK
| | - Nickolay I Hristov
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA Center for Design Innovation, Winston Salem, NC 27101-4019, USA
| | - Sharon M Swartz
- School of Engineering, Brown University, Providence, RI 02912, USA Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
| | - Kenneth S Breuer
- School of Engineering, Brown University, Providence, RI 02912, USA Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
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20
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Maeda M, Nakata T, Kitamura I, Tanaka H, Liu H. Quantifying the dynamic wing morphing of hovering hummingbird. ROYAL SOCIETY OPEN SCIENCE 2017; 4:170307. [PMID: 28989736 PMCID: PMC5627076 DOI: 10.1098/rsos.170307] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 08/14/2017] [Indexed: 05/14/2023]
Abstract
Animal wings are lightweight and flexible; hence, during flapping flight their shapes change. It has been known that such dynamic wing morphing reduces aerodynamic cost in insects, but the consequences in vertebrate flyers, particularly birds, are not well understood. We have developed a method to reconstruct a three-dimensional wing model of a bird from the wing outline and the feather shafts (rachides). The morphological and kinematic parameters can be obtained using the wing model, and the numerical or mechanical simulations may also be carried out. To test the effectiveness of the method, we recorded the hovering flight of a hummingbird (Amazilia amazilia) using high-speed cameras and reconstructed the right wing. The wing shape varied substantially within a stroke cycle. Specifically, the maximum and minimum wing areas differed by 18%, presumably due to feather sliding; the wing was bent near the wrist joint, towards the upward direction and opposite to the stroke direction; positive upward camber and the 'washout' twist (monotonic decrease in the angle of incidence from the proximal to distal wing) were observed during both half-strokes; the spanwise distribution of the twist was uniform during downstroke, but an abrupt increase near the wrist joint was found during upstroke.
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Affiliation(s)
- Masateru Maeda
- School of Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Toshiyuki Nakata
- Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | - Ikuo Kitamura
- Yamaha Motor Co., Ltd, 3078 Arai, Arai-cho, Kosai, Shizuoka 431-0302, Japan
| | - Hiroto Tanaka
- School of Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Hao Liu
- Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
- Shanghai Jiao Tong University and Chiba University International Cooperative Research Center, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
- Author for correspondence: Hao Liu e-mail:
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21
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Chin DD, Matloff LY, Stowers AK, Tucci ER, Lentink D. Inspiration for wing design: how forelimb specialization enables active flight in modern vertebrates. J R Soc Interface 2017; 14:20170240. [PMID: 28592663 PMCID: PMC5493806 DOI: 10.1098/rsif.2017.0240] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 05/15/2017] [Indexed: 12/31/2022] Open
Abstract
Harnessing flight strategies refined by millions of years of evolution can help expedite the design of more efficient, manoeuvrable and robust flying robots. This review synthesizes recent advances and highlights remaining gaps in our understanding of how bird and bat wing adaptations enable effective flight. Included in this discussion is an evaluation of how current robotic analogues measure up to their biological sources of inspiration. Studies of vertebrate wings have revealed skeletal systems well suited for enduring the loads required during flight, but the mechanisms that drive coordinated motions between bones and connected integuments remain ill-described. Similarly, vertebrate flight muscles have adapted to sustain increased wing loading, but a lack of in vivo studies limits our understanding of specific muscular functions. Forelimb adaptations diverge at the integument level, but both bird feathers and bat membranes yield aerodynamic surfaces with a level of robustness unparalleled by engineered wings. These morphological adaptations enable a diverse range of kinematics tuned for different flight speeds and manoeuvres. By integrating vertebrate flight specializations-particularly those that enable greater robustness and adaptability-into the design and control of robotic wings, engineers can begin narrowing the wide margin that currently exists between flying robots and vertebrates. In turn, these robotic wings can help biologists create experiments that would be impossible in vivo.
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Affiliation(s)
- Diana D Chin
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - Laura Y Matloff
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - Amanda Kay Stowers
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - Emily R Tucci
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - David Lentink
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
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22
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Konow N, Cheney JA, Roberts TJ, Iriarte-Díaz J, Breuer KS, Waldman JRS, Swartz SM. Speed-dependent modulation of wing muscle recruitment intensity and kinematics in two bat species. ACTA ACUST UNITED AC 2017; 220:1820-1829. [PMID: 28235906 DOI: 10.1242/jeb.144550] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 02/21/2017] [Indexed: 02/05/2023]
Abstract
Animals respond to changes in power requirements during locomotion by modulating the intensity of recruitment of their propulsive musculature, but many questions concerning how muscle recruitment varies with speed across modes of locomotion remain unanswered. We measured normalized average burst EMG (aEMG) for pectoralis major and biceps brachii at different flight speeds in two relatively distantly related bat species: the aerial insectivore Eptesicus fuscus, and the primarily fruit-eating Carollia perspicillata These ecologically distinct species employ different flight behaviors but possess similar wing aspect ratio, wing loading and body mass. Because propulsive requirements usually correlate with body size, and aEMG likely reflects force, we hypothesized that these species would deploy similar speed-dependent aEMG modulation. Instead, we found that aEMG was speed independent in E. fuscus and modulated in a U-shaped or linearly increasing relationship with speed in C. perspicillata This interspecific difference may be related to differences in muscle fiber type composition and/or overall patterns of recruitment of the large ensemble of muscles that participate in actuating the highly articulated bat wing. We also found interspecific differences in the speed dependence of 3D wing kinematics: E. fuscus modulates wing flexion during upstroke significantly more than C. perspicillata Overall, we observed two different strategies to increase flight speed: C. perspicillata tends to modulate aEMG, and E. fuscus tends to modulate wing kinematics. These strategies may reflect different requirements for avoiding negative lift and overcoming drag during slow and fast flight, respectively, a subject we suggest merits further study.
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Affiliation(s)
- Nicolai Konow
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
| | - Jorn A Cheney
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
| | - Thomas J Roberts
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
| | - Jose Iriarte-Díaz
- Department of Oral Biology, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Kenneth S Breuer
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA.,School of Engineering, Brown University, Providence, RI 02912, USA
| | - J Rhea S Waldman
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA.,Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
| | - Sharon M Swartz
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA.,School of Engineering, Brown University, Providence, RI 02912, USA
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23
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Schunk C, Swartz SM, Breuer KS. The influence of aspect ratio and stroke pattern on force generation of a bat-inspired membrane wing. Interface Focus 2017; 7:20160083. [PMID: 28163875 DOI: 10.1098/rsfs.2016.0083] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Aspect ratio (AR) is one parameter used to predict the flight performance of a bat species based on wing shape. Bats with high AR wings are thought to have superior lift-to-drag ratios and are therefore predicted to be able to fly faster or to sustain longer flights. By contrast, bats with lower AR wings are usually thought to exhibit higher manoeuvrability. However, the half-span ARs of most bat wings fall into a narrow range of about 2.5-4.5. Furthermore, these predictions do not take into account the wide variation in flapping motion observed in bats. To examine the influence of different stroke patterns, we measured lift and drag of highly compliant membrane wings with different bat-relevant ARs. A two degrees of freedom shoulder joint allowed for independent control of flapping amplitude and wing sweep. We tested five models with the same variations of stroke patterns, flapping frequencies and wind speed velocities. Our results suggest that within the relatively small AR range of bat wings, AR has no clear effect on force generation. Instead, the generation of lift by our simple model mostly depends on wingbeat frequency, flapping amplitude and freestream velocity; drag is mostly affected by the flapping amplitude.
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Affiliation(s)
- Cosima Schunk
- School of Engineering , Brown University , Providence, RI 02912 , USA
| | - Sharon M Swartz
- School of Engineering, Brown University, Providence, RI 02912, USA; Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
| | - Kenneth S Breuer
- School of Engineering, Brown University, Providence, RI 02912, USA; Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
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24
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Johansson LC, Håkansson J, Jakobsen L, Hedenström A. Ear-body lift and a novel thrust generating mechanism revealed by the complex wake of brown long-eared bats (Plecotus auritus). Sci Rep 2016; 6:24886. [PMID: 27118083 PMCID: PMC4846812 DOI: 10.1038/srep24886] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 04/06/2016] [Indexed: 11/26/2022] Open
Abstract
Large ears enhance perception of echolocation and prey generated sounds in bats. However, external ears likely impair aerodynamic performance of bats compared to birds. But large ears may generate lift on their own, mitigating the negative effects. We studied flying brown long-eared bats, using high resolution, time resolved particle image velocimetry, to determine the aerodynamics of flying with large ears. We show that the ears and body generate lift at medium to cruising speeds (3–5 m/s), but at the cost of an interaction with the wing root vortices, likely reducing inner wing performance. We also propose that the bats use a novel wing pitch mechanism at the end of the upstroke generating thrust at low speeds, which should provide effective pitch and yaw control. In addition, the wing tip vortices show a distinct spiraling pattern. The tip vortex of the previous wingbeat remains into the next wingbeat and rotates together with a newly formed tip vortex. Several smaller vortices, related to changes in circulation around the wing also spiral the tip vortex. Our results thus show a new level of complexity in bat wakes and suggest large eared bats are less aerodynamically limited than previous wake studies have suggested.
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Affiliation(s)
| | - Jonas Håkansson
- Dept. Biology, Lund University, Ecology building, SE-223 62 Lund, Sweden
| | | | - Anders Hedenström
- Dept. Biology, Lund University, Ecology building, SE-223 62 Lund, Sweden
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25
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Håkansson J, Hedenström A, Winter Y, Johansson LC. The wake of hovering flight in bats. J R Soc Interface 2016; 12:20150357. [PMID: 26179990 DOI: 10.1098/rsif.2015.0357] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Hovering means stationary flight at zero net forward speed, which can be achieved by animals through muscle powered flapping flight. Small bats capable of hovering typically do so with a downstroke in an inclined stroke plane, and with an aerodynamically active outer wing during the upstroke. The magnitude and time history of aerodynamic forces should be reflected by vorticity shed into the wake. We thus expect hovering bats to generate a characteristic wake, but this has until now never been studied. Here we trained nectar-feeding bats, Leptonycteris yerbabuenae, to hover at a feeder and using time-resolved stereoscopic particle image velocimetry in conjunction with high-speed kinematic analysis we show that hovering nectar-feeding bats produce a series of bilateral stacked vortex loops. Vortex visualizations suggest that the downstroke produces the majority of the weight support, but that the upstroke contributes positively to the lift production. However, the relative contributions from downstroke and upstroke could not be determined on the basis of the wake, because wake elements from down- and upstroke mix and interact. We also use a modified actuator disc model to estimate lift force, power and flap efficiency. Based on our quantitative wake-induced velocities, the model accounts for weight support well (108%). Estimates of aerodynamic efficiency suggest hovering flight is less efficient than forward flapping flight, while the overall energy conversion efficiency (mechanical power output/metabolic power) was estimated at 13%.
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Affiliation(s)
| | | | - York Winter
- Department of Cognitive Neurobiology, Humboldt University, Berlin, Germany
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26
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Abstract
Bats are diverse, speciose, and inhabit most of earth’s habitats, aided by powered flapping flight. The many traits that enable flight in these mammals have long attracted popular and research interest, but recent technological and conceptual advances have provided investigators with new kinds of information concerning diverse aspects of flight biology. As a consequence of these new data, our understanding of how bats fly has begun to undergo fundamental changes. Physical and neural science approaches are now beginning to inform understanding of structural architecture of wings. High-speed videography is dramatically expanding documentation of how bats fly. Experimental fluid dynamics and innovative physiological techniques profoundly influence how we interpret the ways bats produce aerodynamic forces as they execute distinctive flight behaviors and the mechanisms that underlie flight energetics. Here, we review how recent bat flight research has provided significant new insights into several important aspects of bat flight structure and function. We suggest that information coming from novel approaches offer opportunities to interconnect studies of wing structure, aerodynamics, and physiology more effectively, and to connect flight biology to newly emerging studies of bat evolution and ecology.
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Affiliation(s)
- S.M. Swartz
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
- School of Engineering, Brown University, Providence, RI 02912, USA
| | - N. Konow
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
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27
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Heerenbrink MK, Johansson LC, Hedenström A. Power of the wingbeat: modelling the effects of flapping wings in vertebrate flight. Proc Math Phys Eng Sci 2015; 471:20140952. [PMID: 27547098 DOI: 10.1098/rspa.2014.0952] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Animal flight performance has been studied using models developed for man-made aircraft. For an aeroplane with fixed wings, the energetic cost as a function of flight speed can be expressed in terms of weight, wing span, wing area and body area, where more details are included in proportionality coefficients. Flying animals flap their wings to produce thrust. Adopting the fixed wing flight model implicitly incorporates the effects of wing flapping in the coefficients. However, in practice, these effects have been ignored. In this paper, the effects of reciprocating wing motion on the coefficients of the fixed wing aerodynamic power model for forward flight are explicitly formulated in terms of thrust requirement, wingbeat frequency and stroke-plane angle, for optimized wingbeat amplitudes. The expressions are obtained by simulating flights over a large parameter range using an optimal vortex wake method combined with a low-level blade element method. The results imply that previously assumed acceptable values for the induced power factor might be strongly underestimated. The results also show the dependence of profile power on wing kinematics. The expressions introduced in this paper can be used to significantly improve animal flight models.
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Affiliation(s)
- M Klein Heerenbrink
- Department of Biology , Lund University , Sölvegatan 37, 223 62 Lund, Sweden
| | - L C Johansson
- Department of Biology , Lund University , Sölvegatan 37, 223 62 Lund, Sweden
| | - A Hedenström
- Department of Biology , Lund University , Sölvegatan 37, 223 62 Lund, Sweden
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28
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Hedenström A, Johansson LC. Bat flight: aerodynamics, kinematics and flight morphology. J Exp Biol 2015; 218:653-63. [DOI: 10.1242/jeb.031203] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
ABSTRACT
Bats evolved the ability of powered flight more than 50 million years ago. The modern bat is an efficient flyer and recent research on bat flight has revealed many intriguing facts. By using particle image velocimetry to visualize wake vortices, both the magnitude and time-history of aerodynamic forces can be estimated. At most speeds the downstroke generates both lift and thrust, whereas the function of the upstroke changes with forward flight speed. At hovering and slow speed bats use a leading edge vortex to enhance the lift beyond that allowed by steady aerodynamics and an inverted wing during the upstroke to further aid weight support. The bat wing and its skeleton exhibit many features and control mechanisms that are presumed to improve flight performance. Whereas bats appear aerodynamically less efficient than birds when it comes to cruising flight, they have the edge over birds when it comes to manoeuvring. There is a direct relationship between kinematics and the aerodynamic performance, but there is still a lack of knowledge about how (and if) the bat controls the movements and shape (planform and camber) of the wing. Considering the relatively few bat species whose aerodynamic tracks have been characterized, there is scope for new discoveries and a need to study species representing more extreme positions in the bat morphospace.
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Affiliation(s)
- Anders Hedenström
- Department of Biology, Lund University, Ecology Building, SE-223 62 Lund, Sweden
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Muijres FT, Christoffer Johansson L, Winter Y, Hedenström A. Leading edge vortices in lesser long-nosed bats occurring at slow but not fast flight speeds. BIOINSPIRATION & BIOMIMETICS 2014; 9:025006. [PMID: 24855067 DOI: 10.1088/1748-3182/9/2/025006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Slow and hovering animal flight creates high demands on the lift production of animal wings. Steady state aerodynamics is unable to explain the forces required and the most commonly used mechanism to enhance the lift production is a leading edge vortex (LEV). Although LEVs increase the lift, they come at the cost of high drag. Here we determine the flow above the wing of lesser long-nosed bats at slow and cruising speed using particle image velocimetry (PIV). We find that a prominent LEV is present during the downstroke at slow speed, but not at cruising speed. Comparison with previously published LEV data from a robotic flapper inspired by lesser long-nosed bats suggests that bats should be able to generate LEVs at cruising speeds, but that they avoid doing so, probably to increase flight efficiency. In addition, at slow flight speeds we find LEVs of opposite spin at the inner and outer wing during the upstroke, potentially providing a control challenge to the animal. We also note that the LEV stays attached to the wing throughout the downstoke and does not show the complex structures found in insects. This suggests that bats are able to control the development of the LEV and potential control mechanisms are discussed.
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Affiliation(s)
- Florian T Muijres
- Department of Biology, Lund University, Ecology Building, SE-223 62 Lund University, Sweden. Department of Biology, Box 351800, 24 Kincaid Hall, University of Washington, Seattle, WA 98195-1800, USA
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30
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Cheney JA, Konow N, Middleton KM, Breuer KS, Roberts TJ, Giblin EL, Swartz SM. Membrane muscle function in the compliant wings of bats. BIOINSPIRATION & BIOMIMETICS 2014; 9:025007. [PMID: 24855069 DOI: 10.1088/1748-3182/9/2/025007] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Unlike flapping birds and insects, bats possess membrane wings that are more similar to many gliding mammals. The vast majority of the wing is composed of a thin compliant skin membrane stretched between the limbs, hand, and body. Membrane wings are of particular interest because they may offer many advantages to micro air vehicles. One critical feature of membrane wings is that they camber passively in response to aerodynamic load, potentially allowing for simplified wing control. However, for maximum membrane wing performance, tuning of the membrane structure to aerodynamic conditions is necessary. Bats possess an array of muscles, the plagiopatagiales proprii, embedded within the wing membrane that could serve to tune membrane stiffness, or may have alternative functions. We recorded the electromyogram from the plagiopatagiales proprii muscles of Artibeus jamaicensis, the Jamaican fruit bat, in flight at two different speeds and found that these muscles were active during downstroke. For both low- and high-speed flight, muscle activity increased between late upstroke and early downstroke and decreased at late downstroke. Thus, the array of plagiopatagiales may provide a mechanism for bats to increase wing stiffness and thereby reduce passive membrane deformation. These muscles also activate in synchrony, presumably as a means to maximize force generation, because each muscle is small and, by estimation, weak. Small differences in activation timing were observed when comparing low- and high-speed flight, which may indicate that bats modulate membrane stiffness differently depending on flight speed.
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Affiliation(s)
- J A Cheney
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
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Cheney JA, Ton D, Konow N, Riskin DK, Breuer KS, Swartz SM. Hindlimb motion during steady flight of the lesser dog-faced fruit bat, Cynopterus brachyotis. PLoS One 2014; 9:e98093. [PMID: 24858194 PMCID: PMC4032239 DOI: 10.1371/journal.pone.0098093] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 04/28/2014] [Indexed: 11/18/2022] Open
Abstract
In bats, the wing membrane is anchored not only to the body and forelimb, but also to the hindlimb. This attachment configuration gives bats the potential to modulate wing shape by moving the hindlimb, such as by joint movement at the hip or knee. Such movements could modulate lift, drag, or the pitching moment. In this study we address: 1) how the ankle translates through space during the wingbeat cycle; 2) whether amplitude of ankle motion is dependent upon flight speed; 3) how tension in the wing membrane pulls the ankle; and 4) whether wing membrane tension is responsible for driving ankle motion. We flew five individuals of the lesser dog-faced fruit bat, Cynopterus brachyotis (Family: Pteropodidae), in a wind tunnel and documented kinematics of the forelimb, hip, ankle, and trailing edge of the wing membrane. Based on kinematic analysis of hindlimb and forelimb movements, we found that: 1) during downstroke, the ankle moved ventrally and during upstroke the ankle moved dorsally; 2) there was considerable variation in amplitude of ankle motion, but amplitude did not correlate significantly with flight speed; 3) during downstroke, tension generated by the wing membrane acted to pull the ankle dorsally, and during upstroke, the wing membrane pulled laterally when taut and dorsally when relatively slack; and 4) wing membrane tension generally opposed dorsoventral ankle motion. We conclude that during forward flight in C. brachyotis, wing membrane tension does not power hindlimb motion; instead, we propose that hindlimb movements arise from muscle activity and/or inertial effects.
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Affiliation(s)
- Jorn A. Cheney
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
- * E-mail:
| | - Daniel Ton
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
| | - Nicolai Konow
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
| | - Daniel K. Riskin
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
| | - Kenneth S. Breuer
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
- School of Engineering, Brown University, Providence, Rhode Island, United States of America
| | - Sharon M. Swartz
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
- School of Engineering, Brown University, Providence, Rhode Island, United States of America
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