Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session M17: Biofluids: Locomotion VIII - Bats and Butterfly Flight |
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Chair: Haibo Dong, University of Virginia Room: 305 |
Tuesday, November 26, 2013 8:00AM - 8:13AM |
M17.00001: Understanding the energy economy of a batoid-inspired flexible fin Florian H.J. Bremer, Stefano Chiazza, Alexander J. Smits Batoid-inspired autonomous underwater vehicles are interesting in that they offer the promise of fast and efficient motion. To investigate the effects of flexibility of the pectoral fins on the energy economy, free-swimming experiments are conducted an artificial fin in flapping motion. The experiments are conducted by initiating a flapping motion in the stationary fin, and by allowing the fin to accelerate to its free-swimming speed while keeping the amplitude and frequency of the actuation constant. The energy economy is derived by continuously measuring velocity and power input. Comparisons are then made among fins of varying flexibility to find the optimal energy economy. [Preview Abstract] |
Tuesday, November 26, 2013 8:13AM - 8:26AM |
M17.00002: The effect of aspect ratio on the generation of lift and drag of a compliant membrane flapping wing Cosima Schunk, Kristen Michaelson, Tristan Paine, Sharon M. Swartz, Kenneth S. Breuer Aspect ratio is frequently used to describe differences between the large variety of bat wing shapes. Bats with high aspect ratio wings are expected to fly with a high efficiency and to have superior lift-to-drag ratios. In contrast, bats with lower aspect ratio wings are thought to exhibit higher maneuverability. However, those assumptions are often based on theoretical models based on fixed wing aerodynamic theory. To examine the performance of highly compliant wings with different aspect ratios in flapping flight, we measure lift and drag generated by a mechanical flapping wing. A two degree of freedom shoulder joint allows for independent control of flapping amplitude and wing sweep. Several bat-like wings with different aspect ratios but identical surface area were built, and tested in a wind tunnel, and the variations of lift and drag over the wingbeat cycle are measured over a flapping frequency range of 2 - 10 Hz. [Preview Abstract] |
Tuesday, November 26, 2013 8:26AM - 8:39AM |
M17.00003: Deconstructing the Essential Elements of Bat Flight Danesh Tafti, Kamal Viswanath, Nagendra Krishnamurthy There are over 1000 bat species worldwide with a wide range of wing morphologies. Bat wing motion is characterized by an active adaptive three-dimensional highly deformable wing surface which is distinctive in its complex kinematics facilitated by the skeletal and skin membrane manipulation, large deviations from the stroke plane, and large wing cambers. In this study we use measured wing kinematics of a fruit bat in a straight line climbing path to study the fluid dynamics and the forces generated by the wing using an Immersed Boundary Method. This is followed by a proper orthogonal decomposition to investigate the dimensional complexity as well as the key kinematic modes used by the bat during a representative flapping cycle. It is shown that the complex wing motion of the fruit bat can mostly be broken down into canonical descriptors of wing motion such as translation, rotation, out of stroke deviation, and cambering, which the bat uses with great efficacy to generate lift and thrust. [Preview Abstract] |
Tuesday, November 26, 2013 8:39AM - 8:52AM |
M17.00004: Lift and thrust generation by a butterfly-like 3D flapping wing model Kosuke Suzuki, Takaji Inamuro The flapping flight of tiny insects such as a butterfly is of fundamental interest not only in biology itself but also in its practical use for the development of micro air vehicles. It is known that a butterfly flaps downward for generating lift force and backward for generating thrust force. In this study, we consider a simple butterfly-like 3D flapping wing model whose body is a thin rod, wings are rigid and rectangular, and wing motion is simplified. We investigate the lift and thrust generation by the butterfly-like flapping wing model by using the immersed boundary-lattice Boltzmann method. Firstly, we compute the lift and thrust forces when the body of the model is fixed for Reynolds numbers in the range of 50 - 1000. In addition, we evaluate the supportable mass for each Reynolds number by using the computed lift force. Secondly, we simulate the free flight where the body can move translationally but cannot rotate. As results, we find that the evaluated supportable mass can be supported even in the free flight, and the wing model with the mass and the Reynolds number of a fruit fly can go upward against the gravity. Finally, we simulate the effect of the rotation of the body. As results, we find that the body has a large pitching motion and consequently gets off-balance. [Preview Abstract] |
Tuesday, November 26, 2013 8:52AM - 9:05AM |
M17.00005: A Simple Analytical Model for Batoid Wake topology and Propulsive Forces Pablo Valdivia y Alvarado, Karthik Srivatsa Batoids swim by forcing waves along their large pectoral fins. These waves determine the topology of the shed wakes and the resulting propulsive forces. An understanding of the relation between fin kinematics and wake topology is essential to control vehicles that use batoid-like fin propulsion. Simulations of the fluid-structure interactions during fin motions provide information of the changes in wake topology and the propulsive forces that result with variations in fin kinematics. However, simulations require computing power usually not available in mobile robots and cannot be used for real time control. An alternative is to develop simple qualitative models whose errors can be compensated by closed loop feedback controllers. Here we describe an analytical model that can be used to predict wake geometry and resulting propulsive forces in batoid-like fins. The model incorporates important fin kinematic parameters such as wave number, amplitude envelope, and flapping frequency. Dye flow visualization and particle image velocimetry along with force measurements confirm the model applicability to batoid-like fin propulsion. [Preview Abstract] |
Tuesday, November 26, 2013 9:05AM - 9:18AM |
M17.00006: Investigation into the Role of Dragonfly Wing Flexibility During Passive Wing Pitch Reversal Yousaf Bajwa, Ventress Williams, Yan Ren, Haibo Dong Wing deformation is a characteristic part of flapping wing flight. In dragonflies, a torsion wave can be observed propagating from the tip to the root during stroke reversal. In this paper, we utilize high-speed photogrammetry and 3d surface reconstruction techniques to quantify wing deformation and kinematics of a dragonfly. We then use finite elements in the absolute nodal coordinate formulation to estimate strain energy in the wing during wing pitch reversal. We use this data to analyze the role of wing structure in facilitating wing rotation and bringing about the characteristic torsion wave. The influence of the elastic force in facilitating wing rotation is then compared with inertial and aerodynamic forces as well. A quantitative look into the variation of strain energy within the insect wing during wing rotation could lead to more efficient design of dynamic wing pitching mechanisms. [Preview Abstract] |
Tuesday, November 26, 2013 9:18AM - 9:31AM |
M17.00007: Analysis of Dragonfly Take-off Mechanism: Initial Impulse Generated by Aerodynamic Forces Ruijie Zhu, Ayodeji Bode-Oke, Yan Ren, Haibo Dong Take-off is a critical part of insect flight due to not only that every single flight initiates from take-off, but also that the take-off period, despite its short duration, accounts for a relatively large fraction of the total energy consumption. Thus, studying the mechanism of insect take-off will help to improve the design of Micro Air Vehicles (MAVs) in two major properties, the success rate and the energy efficiency of take-off. In this work, we study 20 cases in which dragonflies (species including \textit{Pachydiplax longipennis}, \textit{Epitheca Cynosura}, \textit{Epitheca princeps} etc.) take off from designed platform. By high-speed photogrammetry, 3-d reconstruction and numerical simulation, we explore how dragonflies coordinate different body parts to help take-off. We evaluate how aerodynamic forces generated by wing flapping create the initial impulse, and how these forces help save energy consumption. [Preview Abstract] |
Tuesday, November 26, 2013 9:31AM - 9:44AM |
M17.00008: Force production of a hovering hummingbird Haoxiang Luo, Jialei Song, Tyson Hedrick A three-dimensional numerical study is performed for a hovering Ruby-throated hummingbird ({\it Archilochus colubris}) based on an immersed-boundary method. To accurately model the unsteady aerodynamics, realistic 3D wing kinematics is reconstructed from high-speed images of the wing motion filmed at 1000 frames per second, resulting in 25 frames per flapping cycle. A high-resolution grid is employed to resolve the vortices shed from the wing. The results are validated by comparing the spanwise vorticity and circulation with the previous PIV data and also by calculating the average lift. The force production shows significant asymmetry with the downstroke producing lift 2.6 times as high as the upstroke, despite a nearly horizontal stroke plane. The total power consumption is around 55 W/kg, which is twice of previous estimate. In this presentation, we will discuss several mechanisms that lead to the force asymmetry, including the drag-based lift and the leading-edge vortex behavior. We will also address the role of wing-wake interaction, which appears to be different for the hummingbird than some of the insects such as fruit flies. [Preview Abstract] |
Tuesday, November 26, 2013 9:44AM - 9:57AM |
M17.00009: Investigation of sharp-turning mechanism of damselfly via motion kinematics and vortex dynamics Yu-Chen Tsai, Jing-Tang Yang Damselflies often perform unconventional backward flight to make sharp turns while changing direction in forward flight. The mechanism of rapid transition between forward and backward flight of the free-flying damselfly (Psolodesmus mandarinus) is experimentally investigated in this study. The flapping kinematics of the damselflies during flight reversal is observed and recorded by using two high-speed cameras. The flow field is examined first and the vortex structure is further analyzed by using particle imaging velocimetry (PIV) technique. The relation between the kinematic parameters of a moving damselfly and its excellent turning ability is revealed; the damselfly makes a sharp turn in merely tens of milliseconds by altering body posture, flapping frequency, and angle of attack. The strong interaction between the wings and the surrounding vortices is proved crucial in producing forces needed for turning. This study provides insights into the maneuvering strategy of flying insects. [Preview Abstract] |
Tuesday, November 26, 2013 9:57AM - 10:10AM |
M17.00010: The mechanism of body rotation in the flapping flight of butterflies Yueh-Han Fei, Jing-Tang Yang The aerodynamic effects of the body rotation on the flapping flying of butterflies are experimentally and numerically investigated. We first observe and record the flying motion of a butterfly (Kallima inachus) in free flight, focusing especially on the body rotation, via two high speed video cameras and PIV. The body rotation is found in phase with wing flapping while the abdomen is out of phase with wing flapping. Further, we establish the model of flexible wings of a butterfly and exploit the fluid dynamics analysis via the dynamic mesh technique to study the contribution of body rotation to the lift. The results reveal that the body rotation is capable of strengthening the vortex ring structure and correspondingly enhancing the efficiency of lift production. Our simulation model shows the body rotation contributes 15{\%} of total lift. The results of this study may serve as a useful guide for designing insect-like MAVs in the future. [Preview Abstract] |
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