Control of gliding in a flying snake-inspired
                    <i>n</i>
                    -chain model

Jafari, Farid; Tahmasian, Sevak; Ross, Shane D.; Socha, John J.

doi:10.1088/1748-3190/aa8c2f

Cited by 11 publications

(5 citation statements)

References 43 publications

(50 reference statements)

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“…To test the existing hypotheses, these results should be incorporated into theoretical studies of the dynamics of flying snakes. Previous efforts (Jafari et al, 2014(Jafari et al, , 2017 have only considered the aerodynamic properties of a single, isolated airfoil, but clearly tandem interactions must be considered for a more accurate understanding of real snake gliding.…”

Section: Discussionmentioning

confidence: 99%

“…Bahlman et al, 2013;Wang et al, 2014;Shyy et al, 2009;Song et al, 2014;Muijres et al, 2008;Lentink and Dickinson, 2009;Bomphrey et al, 2006), but the snake's large advance ratio (the ratio of the forward motion to the reciprocating motion) compared with that of insects and birds (Vogel, 2003;Dickson and Dickinson, 2004;Holden et al, 2014) suggests that unsteady mechanisms are less likely to produce a significant aerodynamic contribution. Recent studies (Jafari et al, 2017;Yeaton et al, 2020) found that undulation does have a functional influence on glide performance, acting to increase the stability of the snake. However, the theoretical modeling of the snake only incorporated single-foil aerodynamic coefficients, and did not examine interactive aerodynamics.…”

Section: Introductionmentioning

confidence: 99%

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The aerodynamics of flying snake airfoils in tandem configuration

Jafari

Holden

LaFoy

et al. 2021

Journal of Experimental Biology

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Flying snakes flatten their body to form a roughly triangular cross-sectional shape, enabling lift production and horizontal acceleration. While gliding, they also assume an S-shaped posture, which could promote aerodynamic interactions between the fore and the aft body. Such interactions have been studied experimentally; however, very coarse models of the snake's cross-sectional shape were used, and the effects were measured only for the downstream model. In this study, the aerodynamic interactions resulting from the snake's posture were approximated using two-dimensional anatomically accurate airfoils positioned in tandem to mimic the snake's geometry during flight. Load cells were used to measure the lift and drag forces, and flow field data were obtained using digital particle image velocimetry (PIV). The results showed a strong dependence of the aerodynamic performance on the tandem arrangement, with the lift coefficients being generally more influenced than the drag coefficients. Flow field data revealed that the tandem arrangement modified the separated flow and the wake size, and enhanced the lift in cases in which the wake vortices formed closer to the models, producing suction on the dorsal surface. The downforce created by the flow separation from the ventral surface of the models at 0° angle of attack was another significant factor contributing to lift production. A number of cases showing large variations of aerodynamic performance included configurations close to the most probable posture of airborne flying snakes, suggesting that small postural variations could be used to control the glide trajectory.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The aerodynamics of flying snake airfoils in tandem configuration

Jafari

Holden

LaFoy

et al. 2021

Journal of Experimental Biology

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“…The single flying snake species tested here, C. ornata, does not glide as well as C. paradisi (Socha & LaBarbera, 2005). Both cross-sectional shape (Holden et al, 2014;Krishnan et al, 2014) and relative body posture are important for the generation of aerodynamic forces, and undulatory patterns additionally influence the snake's stability characteristics (Jafari et al, 2014(Jafari et al, , 2017Yeaton et al, 2020). It is possible that skin-propertyrelated features may influence differences in flattening ability and ability to produce specific kinematics in the air, and thus the locomotor performance of the snake during gliding.…”

Section: Study Limitationsmentioning

confidence: 96%

Material properties of skin in the flying snake Chrysopelea ornata

et al. 2022

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The genus Chrysopelea encompasses the "flying" snakes. This taxon has the ability to glide via lateral aerial undulation and dorsoventral body flattening, a skill unique to this group, but in addition to other functions common to all colubrids. The skin must be extensible enough to allow this body shape alteration and undulation, and strong enough to withstand the forces seen during landing. For this reason, characterizing the mechanical properties of the skin may give insight to the functional capabilities of the skin during these gliding and landing behaviors. Dynamic and viscoelastic uniaxial tensile tests were combined with a modified particle image velocimetry technique to provide strength, extensibility, strain energy, and stiffness information about the skin with respect to orientation, region, and species, along with viscoelastic parameters. Results compared with two other species in this study and a broader range of species in prior studies indicate that while the skin of these unique snakes may not be specifically specialized to deal with larger forces, extensibility, or energy storage and release, the skin does have increased strength and energy storage associated with higher strain rates. The skin also has differing properties with respect to dorsoventral location, and regional differences in strength in the circumferential orientation. This may indicate that, although the properties of the skin may not be different, the rate at which the skin is strained in the different species may vary, thus altering the apparent properties of the skin during specific behaviors.iii DedicationTo Matthew… For all your love and support, thank you.First, I would like to thank the members of my committee, Dr. Pavlos Vlachos and Dr.Raffaella De Vita for their continuous help throughout this study. I would also like to acknowledge the other members of the DARPA snake team and AEThER lab for their helpful suggestions and assistance with image correlation. Next I must thank, my advisor, Dr. Jake Socha, not only for his for his continual guidance and assistance in this study, but also for helping me to see the bigger picture. I would also like to thank Carolyn Roberts for her assistance with dissection and experimental testing. Funding for this project was provided by DARPA.I would also like to thank my family, biological or not, for constantly encouraging me through this. Lastly, I would like to not only thank anyone who has sent up a prayer for me, but most especially the One answering them. v Table of ContentsDedication .

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“…Measurements were conducted over angles of attack from −10 • to 60 • . A variety of methods have been applied to understand and model this animal's behavior [1,6,24,[34][35][36][37]. Here, we analyze how a fixed glider with the snake's characteristics would behave, similar to the work of Jafari et al [35].…”

Section: 22mentioning

confidence: 99%

Global phase space structures in a model of passive descent

Nave

Ross

2019

Communications in Nonlinear Science and Numerical Simulation

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Even the most simplified models of falling and gliding bodies exhibit rich nonlinear dynamical behavior. Taking a global view of the dynamics of one such model, we find an attracting invariant manifold that acts as the dominant organizing feature of trajectories in velocity space. This attracting manifold captures the final, slowly changing phase of every passive descent, providing a higher-dimensional analogue to the concept of terminal velocity, the terminal velocity manifold. Within the terminal velocity manifold in extended phase space, there is an equilibrium submanifold with equilibria of alternating stability type, with different stability basins. In this work, we present theoretical and numerical methods for approximating the terminal velocity manifold and discuss ways to approximate falling and gliding motion in terms of these underlying phase space structures.in the work of Maxwell and Zhukovskii [12][13][14]. Prior experimental studies have identified several canonical behaviors exhibited by falling disks, plates, and plant seeds characterized by different couplings between rotation and translation in space [2,15]. In all of these behaviors, an inherently high-dimensional system, which must consider velocities, angles, and angular velocities in 3D space, converges to a low-dimensional behavior, whether traveling in a single plane or going through a cycle of velocities [15][16][17][18][19][20].Mathematical models have offered many insights into passive descent. Ideal flow theory has been used to study the motion of a body both through a steady fluid and interacting with shed vortices [13,[21][22][23]. The Zhukovskii problem or phugoid model, which assumes that the wing travels with constant angle-of-attack, is a two-dimensional ordinary differential equation for flight from which phugoid oscillations, which couple forward velocity with pitch angle, arise [14]. Andersen et al. developed a phenomenological model based on experiments and simulations which produce fluttering, tumbling, and even chaotic behavior through a 4D differential equation [17,18]. To focus specifically on gliding animal flight and compare the gliding capabilities of different animals, Yeaton et al. [24] introduced a two-dimensional model for non-equilibrium gliding of animals. It is a modification of this model which we will consider in the present work. In this model, the authors decoupled translational and rotational dynamics in order to take a deeper view of the translational behavior and shape dependence based on lift and drag characteristics alone. To do so, inspired by the motion of gliding animals, the authors treat pitch angle as fixed with respect to the ground, assuming that the glider has some amount of control to hold this angle. Lift and drag are treated as functional parameters in this model, which is used to capture the differences in glider shapes. This model works especially well for gliding animals, but may be extended to general passive descent. Yeaton et al. [24] analyzed a variety of animal gliders and found tha...

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Control of gliding in a flying snake-inspired n -chain model

Cited by 11 publications

References 43 publications

The aerodynamics of flying snake airfoils in tandem configuration

The aerodynamics of flying snake airfoils in tandem configuration

Material properties of skin in the flying snake Chrysopelea ornata

Global phase space structures in a model of passive descent

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