Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session L15: Biofluids: Insect Flight |
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Chair: Tadd Truscott, Brigham Young University Room: 28A |
Monday, November 19, 2012 3:35PM - 3:48PM |
L15.00001: Low Reynolds Number Drag Alteration Inspired by Butterfly Scales Brent LaForte, Courtney Kronenberger, Amy Lang Biomimetics is the process of looking towards nature's adaptations for answers to today's engineering obstacles. An age-old engineering dilemma is trying to find new methods to reduce the amount of drag over a body. This research finds inspiration from butterfly scales which are hypothesized to alter surface friction over the wings. Drop testing was performed on axisymmetric, streamlined, teardrop models which were rapid-prototyped such that the surface was covered with either streamwise or transverse cavities modeled after the Monarch butterfly. The drop tank contained silicone oil with a viscosity two hundred times that of water insuring flow similarity between the model cavities (2.5 mm cavity depth) and the butterfly scale structures (about 30 microns cavity depth). A variation in Reynolds number was achieved by altering the model weight such that terminal speeds ranged from 5 to 70 cm/s. Results showed a reduction in surface friction for the transverse cavity configurations based on the roller-bearing effect. These findings suggest that the cavity shape and ratio is directly correlated to the amount of drag alteration. [Preview Abstract] |
Monday, November 19, 2012 3:48PM - 4:01PM |
L15.00002: Rock and Roll - How Do Flies Recover From Serial Stumbles? Tsevi Beatus, John Guckenheimer, Itai Cohen Flying insects manage to maintain aerodynamic stability despite the facts that flapping flight is inherently unstable and that they are constantly subject to mechanical perturbations, such as gusts of wind. To maintain stability against such perturbations, insects rely on fast and robust flight control mechanisms, which are poorly understood. Here, we \textit{directly} study flight control in the fruit fly \textit{D. melanogaster} by applying mechanical perturbations in mid-air and measuring the insects' correction maneuvers. On each fly we glue a small magnet and use pulses of magnetic field to apply torque perturbations along the fly's roll axis. We then use high-speed filming and 3D reconstruction to characterize the kinematics of their correction maneuver and show how the flies fully recover from roll perturbations of up to 70$^{\circ}$ within 7-8 wing beats (30-40ms), which is faster than their visual response time. In addition, we study the dynamics of the maneuver by calculating the aerodynamic forces and torques the fly produces. Finally, we present a control mechanism that can explain the roll correction maneuver. These results have implications ranging from the neurobiological mechanisms that underlie flight control to the design of flapping robots. [Preview Abstract] |
Monday, November 19, 2012 4:01PM - 4:14PM |
L15.00003: Scales affect performance of Monarch butterfly forewings in autorotational flight Anya Demko, Amy Lang Butterfly wings are characterized by rows of scales (approximately 100 microns in length) that create a shingle-like pattern of cavities over the entire surface. It is hypothesized that these cavities influence the airflow around the wing and increase aerodynamic performance. A forewing of the Monarch butterfly (\textit{Danus plexippus}) naturally undergoes autorotational flight in the laminar regime. Autorotational flight is an accurate representation of insect flight because the rotation induces a velocity gradient similar to that found over a flapping wing. Drop test flights of 22 forewings before and after scale removal were recorded with a high-speed camera and flight behavior was quantified. It was found that removing the scales increased the descent speed and decreased the descent factor, a measure of aerodynamic efficacy, suggesting that scales increased the performance of the forewings. [Preview Abstract] |
Monday, November 19, 2012 4:14PM - 4:27PM |
L15.00004: Flow Modulation and Force Control in Insect Fast Maneuver Chengyu Li, Haibo Dong, Wen Zhang, Kuo Gai In this work, an integrated study combining high-speed photogrammetry and direct numerical simulation (DNS) is used to study free flying insects in fast maneuver. Quantitative measurement has shown the significant differences between quad-winged flyers such as dragonfly and damselfly and two-winged flyers such as cicada. Comparisons of unsteady 3D vortex formation and associated aerodynamic force production reveal the different mechanisms used by insects in fast turn. This work is supported by NSF CBET-1055949. [Preview Abstract] |
Monday, November 19, 2012 4:27PM - 4:40PM |
L15.00005: On the Optimal Dynamic Camber Formation in Insect Flight Yan Ren, Haibo Dong It is widely thought that wing flexibility and wing deformation could significantly affect aerodynamic force productions over completely rigid wings in insect flights. However, there is a lack of quantitative discussion of dynamic formation of wing camber and its effect on wing's aerodynamic performance. In this work, a deformable wing is used to model the wing camber and its dynamic formation. A Direct Numerical Simulation (DNS) based computational optimization frame has been developed to obtain the optimal dynamic camber formation of dragonfly in takeoff and cruising flight. Comparative study is then performed between the optimized flexible wing and real dragonfly wing. Results have shown the maximum camber happens around 30{\%} (downstroke) and 80{\%} (upstroke) of one wing beat. Force production and unsteady flows of the flexible wing are also discussed. [Preview Abstract] |
Monday, November 19, 2012 4:40PM - 4:53PM |
L15.00006: Quantifying Dragonfly Kinematics During Unsteady Free-Flight Maneuvers James Melfi, Huai-ti Lin, Matteo Mischiati, Anthony Leonardo, Z. Jane Wang What make dragonflies such interesting fliers are the unsteady high-speed aerial maneuvers they perform. Until recently, the study of dragonflies in mid-flight has been limited to steady-state motions such as hovering and forward flight. In this talk, we report our kinematic analyses of the dragonfly flight recorded in a custom dragonfly arena at HHMI, Janelia Farm. Dragonfly's turning motions often involve all three degrees of freedom about its body axes: yaw, roll, and pitch. We examine the wing kinematics changes associated with different turning maneuvers, and seek the key variables in the wing kinematics that are responsible for each specific maneuver. [Preview Abstract] |
Monday, November 19, 2012 4:53PM - 5:06PM |
L15.00007: Whole-field, time resolved velocity measurements of flow structures on insect wings during free flight Kenneth Langley, Scott Thomson, Tadd Truscott The development of micro air vehicles (MAVs) that are propelled using flapping flight necessitates an understanding of the unsteady aerodynamics that enable this mode of flight. Flapping flight has been studied using a variety of methods including computational models, experimentation and observation. Until recently, the observation of natural flyers has been limited to qualitative methods such as smoke-line visualization. Advances in imaging technology have enabled the use of particle image velocimetry (PIV) to gain a quantitative understanding of the unsteady nature of the flight. Previously published PIV studies performed on insects have been limited to velocities in a single plane on tethered insects in a wind tunnel. We present the three-dimensional, time-resolved velocity fields of flight around a butterfly, using an array of high-speed cameras at 1 kHz through a technique known as 3D Synthetic Aperture PIV (SAPIV). These results are useful in understanding the relationship between wing kinematics and the unsteady aerodynamics generated. [Preview Abstract] |
Monday, November 19, 2012 5:06PM - 5:19PM |
L15.00008: Mosquito flight failure in heavy fog Andrew Dickerson, Luke Telljohann, Lee-Ellen Thornton, Caitlin Moyer, David Hu Mosquitoes thrive during rainfall and high humidity. We previously found that mosquitoes are successful fliers through rainfall. Heavy fog, consisting of drops three orders of magnitude smaller in mass than raindrops, presents an environment in which mosquitoes cannot maintain flight. Through high-speed videography, we observe mosquitoes reduce wingbeat frequency in heavy fog, but retain the ability to generate sufficient force to lift their bodies, even after significant dew deposition. They are unable, however, to maintain an upright position required for sustainable flight. A mosquito's primary flight control mechanism is its halteres, small knobbed structures evolved from the hind wings, which flap anti-phase with the wings and provide gyroscopic feedback through Coriolis forces. Though the halteres are hydrophobic, repeated collisions with 10-micron fog particles hinders flight control, leading to flight failure. [Preview Abstract] |
Monday, November 19, 2012 5:19PM - 5:32PM |
L15.00009: Numerical study of insect free hovering flight Di Wu, Khoon Seng Yeo, Tee Tai Lim In this paper we present the computational fluid dynamics study of three-dimensional flow field around a free hovering fruit fly integrated with unsteady FSI analysis and the adaptive flight control system for the first time. The FSI model being specified for fruitfly hovering is achieved by coupling a structural problem based on Newton's second law with a rigorous CFD solver concerning generalized finite difference method. In contrast to the previous hovering flight research, the wing motion employed here is not acquired from experimental data but governed by our proposed control systems. Two types of hovering control strategies i.e. stroke plane adjustment mode and paddling mode are explored, capable of generating the fixed body position and orientation characteristic of hovering flight. Hovering flight associated with multiple wing kinematics and body orientations are shown as well, indicating the means by which fruitfly actually maintains hovering may have considerable freedom and therefore might be influenced by many other factors beyond the physical and aerodynamic requirements. Additionally, both the near- and far-field flow and vortex structure agree well with the results from other researchers, demonstrating the reliability of our current model. [Preview Abstract] |
Monday, November 19, 2012 5:32PM - 5:45PM |
L15.00010: Numerical Simulation of \textit{Drophila} Flight Based on Arbitrary Langrangian-Eulerian Method Belkis Erzincanli, Mehmet Sahin A parallel unstructured finite volume algorithm based on Arbitrary Lagrangian Eulerian (ALE) method has been developed in order to investigate the wake structure around a pair of flapping \textit{Drosophila} wings. The numerical method uses a side-centered arrangement of the primitive variables that does not require any \textit{ad-hoc} modifications in order to enhance pressure coupling. A radial basis function (RBF) interpolation method is also implemented in order to achieve large mesh deformations. For the parallel solution of resulting large-scale algebraic equations, a matrix factorization is introduced similar to that of the projection method for the whole coupled system and two-cycle of BoomerAMG solver is used for the scaled discrete Laplacian provided by the HYPRE library which we access through the PETSc library. The present numerical algorithm is initially validated for the flow past an oscillating circular cylinder in a channel and the flow induced by an oscillating sphere in a cubic cavity. Then the numerical algorithm is applied to the numerical simulation of flow field around a pair of flapping \textit{Drosophila} wing in hover flight. The time variation of the near wake structure is shown along with the aerodynamic loads and particle traces. [Preview Abstract] |
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