Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session L27: Biofluids: Insect Flight: Dynamics and Control |
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Chair: Z Jane Wang, Cornell University Room: 308 |
Monday, November 23, 2015 4:05PM - 4:18PM |
L27.00001: Initial Observations of Fruit Fly;s Flight with its b1 Motor Neuron Altered Z Jane Wang, James Melfi Jr Recently we have suggested that one of the fly's 17 steering muscles, the first basalar muscle (b1) is responsible for maintaining flight stability [1]. To test this, we compare the flight behavior of normal flies with genetically modified flies whose motor neuron to the b1 muscle is silenced. We report our initial observation of the difference and similarity between these two lines supplied by Janelia Farm. We also discuss the basic question for quantifying flight, what makes a good flier? Reference: [1] S Chang and ZJ Wang, Predicting fruit fly's sensing rate with insect flight simulations, PNAS, (2014) [Preview Abstract] |
Monday, November 23, 2015 4:18PM - 4:31PM |
L27.00002: Flight stability analysis under changes in insect morphology Robert Noest, Z. Jane Wang Insect have an amazing ability to control their flight, being able to perform both fast aerial maneuvers and stable hovering. The insect's neural system has developed various mechanism by which it can control these flying feats, but we expect that insect morphology is equally important in facilitating the aerial control. We perform a computational study using a quasi-steady instantaneous flapping flight model which allows us to freely adapt the insect's morphological parameters. We picked a fruit fly as the basis for the body shape and wing motion, and study the effect of changes to the morphology for a range of wing stroke amplitudes. In each case we determine the periodic flight mode, with the period equal to a single wing beat, and do a Floquet stability analysis of the flight. To interpret our results we will compare the changed morphology to related insects. We discuss the implications of the insects location on the stability diagram. [Preview Abstract] |
Monday, November 23, 2015 4:31PM - 4:44PM |
L27.00003: Sparse Sensing of Aerodynamic Loads on Insect Wings Krithika Manohar, Steven Brunton, J. Nathan Kutz We investigate how insects use sparse sensors on their wings to detect aerodynamic loading and wing deformation using a coupled fluid-structure model given periodically flapping input motion. Recent observations suggest that insects collect sensor information about their wing deformation to inform control actions for maneuvering and rejecting gust disturbances. Given a small number of point measurements of the chordwise aerodynamic loads from the sparse sensors, we reconstruct the entire chordwise loading using $\textit{sparse sensing}$ - a signal processing technique that reconstructs a signal from a small number of measurements using $l_1$ norm minimization of sparse modal coefficients in some basis. We compare reconstructions from sensors randomly sampled from probability distributions biased toward different regions along the wing chord. In this manner, we determine the preferred regions along the chord for sensor placement and for estimating chordwise loads to inform control decisions in flight. [Preview Abstract] |
Monday, November 23, 2015 4:44PM - 4:57PM |
L27.00004: Wing-pitch modulation in maneuvering fruit flies is explained by an interplay between aerodynamics and a torsional spring Tsevi Beatus, Itai Cohen While the wing kinematics of many flapping insects have been well characterized, understanding the underlying physiological mechanisms that determine these kinematics is still a challenge. Two of the main difficulties arise from the complexity of the interaction between a flapping wing and its own unsteady flow, as well as the intricate mechanics the insect wing-hinge, which is among the most complicated joints in the animal kingdom. These difficulties call for the application of reduced-order approaches. Here, we model the torques exerted by the wing-hinge along the wing-pitch axis of maneuvering fruit flies as a damped torsional spring with elastic and damping coefficients as well as a rest angle. Furthermore, we model the air flows using simplified quasi-static aerodynamics. Our findings suggest that flies take advantage of the passive coupling between aerodynamics and the damped torsional spring to indirectly control their wing-pitch kinematics by modulating the spring damping and elastic coefficients. These results, in conjunction with the previous literature, indicate flies can accurately control their wing-pitch kinematics on a sub-wing-beat time-scale by modulating all three effective spring parameters on longer time-scales. [Preview Abstract] |
Monday, November 23, 2015 4:57PM - 5:10PM |
L27.00005: Uncontrolled Stability in Freely Flying Insects James Melfi Jr., Z. Jane Wang One of the key flight modes of a flying insect is longitudinal flight, traveling along a localized two-dimensional plane from one location to another. Past work on this topic has shown that flying insects, unless stabilized by some external stimulus, are typically unstable to a well studied pitching instability. In our work, we examine this instability in a computational study to understand whether it is possible for either evolution or an aero-vehicle designer to stabilize longitudinal flight through changes to insect morphology, kinematics, or aerodynamic quantities. A quasi-steady wingbeat averaged flapping flight model is used to describe the insect. From this model, a number of non-dimensional parameters are identified. The effect of these parameters was then quantified using linear stability analysis, applied to various translational states of the insect. Based on our understanding of these parameters, we demonstrate how to find an intrinsically stable flapping flight sequence for a dragonfly-like flapping flier in an instantaneous flapping flight model. [Preview Abstract] |
Monday, November 23, 2015 5:10PM - 5:23PM |
L27.00006: Flapping of Insectile Wings Yangyang Huang, Eva Kanso Insects use flight muscles attached at the base of the wings to produce impressive wing flapping frequencies. Yet the effects of muscle stiffness on the performance of insect wings remain unclear. Here, we construct an insectile wing model, consisting of two rigid wings connected at their base by an elastic torsional spring and submerged in an oscillatory flow. The wing system is free to rotate and flap. We first explore the extent to which the flyer can withstand roll perturbations, then study its flapping behavior and performance as a function of spring stiffness. We find an optimal range of spring stiffness that results in large flapping amplitudes, high force generation and good storage of elastic energy. We conclude by conjecturing that insects may select and adjust the muscle spring stiffness to achieve desired movement. These findings may have significant implications on the design principles of wings in micro air-vehicles. [Preview Abstract] |
Monday, November 23, 2015 5:23PM - 5:36PM |
L27.00007: Kinematics and Aerodynamics of Backward Flying Dragonflies Ayodeji Bode-Oke, Samane Zeyghami, Haibo Dong Highly maneuverable insects such as dragonflies have a wide range of flight capabilities; precise hovering, fast body reorientations, sideways flight and backward takeoff are only a few to mention. In this research, we closely examined the kinematics as well as aerodynamics of backward takeoff in dragonflies and compared them to those of forward takeoff. High speed videography and accurate 3D surface reconstruction techniques were employed to extract details of the wing and body motions as well as deformations during both flight modes. While the velocities of both forward and backward flights were similar, the body orientation as well as the wing kinematics showed large differences. Our results indicate that by tilting the stroke plane angle of the wings as well as changing the orientation of the body relative to the flight path, dragonflies control the direction of the flight like a helicopter. In addition, our detailed analysis of the flow in these flights shows important differences in the wake capture phenomena among these flight modes. [Preview Abstract] |
Monday, November 23, 2015 5:36PM - 5:49PM |
L27.00008: Beetle wings are inflatable origami Rui Chen, Jing Ren, Siqin Ge, David Hu Beetles keep their wings folded and protected under a hard shell. In times of danger, they must unfold them rapidly in order for them to fly to escape. Moreover, they must do so across a range of body mass, from 1 mg to 10 grams. How can they unfold their wings so quickly? We use high-speed videography to record wing unfolding times, which we relate to the geometry of the network of blood vessels in the wing. Larger beetles have longer unfolding times. Modeling of the flow of blood through the veins successfully accounts for the wing unfolding speed of large beetles. However, smaller beetles have anomalously short unfolding times, suggesting they have lower blood viscosity or higher driving pressure. The use of hydraulics to unfold complex objects may have implications in the design of micro-flying air vehicles. [Preview Abstract] |
Monday, November 23, 2015 5:49PM - 6:02PM |
L27.00009: Comparative study of solid and bristled wings in flapping flight of tiny insects Christopher Terrill, Arvind Santhanakrishnan Small insects such as thrips that are less than 1 mm in size fly at Reynolds numbers (Re) on the order of 10 and use wing-wing interaction during flapping. In this interaction, referred to as `clap-and-fling', the wings come in close contact with each other at the end of upstroke and rotate about the trailing edge during start of downstroke. The wings of these tiny insects consist of an array of bristles as opposed to a solid membrane. The goal of this study is to examine the effects of bristled wings on aerodynamic force generation and flow structures compared to solid wings. We used an experimental model for the study in which two model wings were prescribed to move along a simplified 2D representation of clap-and-fling kinematics. Forces were measured through the use of strain gauges and 2D phase-locked particle image velocimetry (PIV) was used to visualize the flow generated from flapping. The PIV results show that circulation of the leading edge vortices (LEVs) is attenuated when bristled wings are used. However, improved drag reduction is observed in the bristled wings. Aerodynamic efficiency variation with Re will be discussed. [Preview Abstract] |
Monday, November 23, 2015 6:02PM - 6:15PM |
L27.00010: Aerodynamics of a beetle in take-off flights Boogeon Lee, Hyungmin Park, Sun-Tae Kim In the present study, we investigate the aerodynamics of a beetle in its take-off flights based on the three-dimensional kinematics of inner (hindwing) and outer (elytron) wings, and body postures, which are measured with three high-speed cameras at 2000 fps. To track the highly deformable wing motions, we distribute 21 morphological markers and use the modified direct linear transform algorithm for the reconstruction of measured wing motions. To realize different take-off conditions, we consider two types of take-off flights; that is, one is the take-off from a flat ground and the other is from a vertical rod mimicking a branch of a tree. It is first found that the elytron which is flapped passively due to the motion of hindwing also has non-negligible wing-kinematic parameters. With the ground, the flapping amplitude of elytron is reduced and the hindwing changes its flapping angular velocity during up and downstrokes. On the other hand, the angle of attack on the elytron and hindwing increases and decreases, respectively, due to the ground. These changes in the wing motion are critically related to the aerodynamic force generation, which will be discussed in detail. [Preview Abstract] |
Monday, November 23, 2015 6:15PM - 6:28PM |
L27.00011: Interaction of the elytra and hind wing of a rhinoceros beetle (\textit{Trypoxylus dichotomus}) during a take-off mode Seungyoung Oh, Sehyeong Oh, Haecheon Choi, Boogeon Lee, Hyungmin Park, Sun-Tae Kim The elytra are a pair of hardened wings that cover the abdomen of a beetle to protect beetle’s hind wings. During the take-off, these elytra open and flap in phase with the hind wings. We investigate the effect of the elytra flapping on beetle’s aerodynamic performance. Numerical simulations are performed at Re=10,000 (based on the wingtip mean velocity and mean chord length of the hind wing) using an immersed boundary method. The simulations are focused on a take-off, and the wing kinematics used is directly obtained from the experimental observations using high speed cameras. The simulation result shows three-dimensional vortical structures generated by the hind wing of the beetle and their interaction with the elytra. The presence of elytra has a negative effect on the lift generation by the hind wings, but the lift force on the elytra themselves is negligible. Further discussions on the elytra - hind wing interaction will be provided during the presentation. [Preview Abstract] |
Monday, November 23, 2015 6:28PM - 6:41PM |
L27.00012: Numerical and Experimental Investigation of Flow Structures During Insect Flight Camli Badrya, James D. Baeder Insect flight kinematics involves complex interplay between aerodynamics structural response and insect body control. Features such as cross-coupling kinematics, high flapping frequencies and geometrical small-scales, result in experiments being challenging to perform. In this study OVERTURNS, an in-house 3D compressible Navier–Stokes solver is utilized to simulate the simplified kinematics of an insect wing in hover and forward flight. The flapping wings simulate the full cycle of wing motion, i.e., the upstroke, downstroke, pronation and supination.The numerical results show good agreement against experimental data in predicting the lift and drag over the flapping cycle. The flow structures around the flapping wing are found to be highly unsteady and vortical. Aside from the tip vortex on the wings, the formation of a prominent leading edge vortex (LEV) during the up/down stroke portions, and the shedding of a trailing edge vortex (TEV) at end of each stroke were observed. Differences in the insect dynamics and the flow features of the LEV are observed between hover and forward flight. In hover the up and downstroke cycles are symmetric, whereas in forward flight, these up and downstroke are asymmetric and LEV strength varies as a function of the kinematics and advance ratio. [Preview Abstract] |
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