Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session G27: Biological Fluid Dynamics: Insect Flight II |
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Chair: Jane Wang, Cornell University Room: 609 |
Sunday, November 24, 2019 3:48PM - 4:01PM |
G27.00001: Dragonfly's Righting Reflex Z. Jane Wang, James Melfi Jr, Anthony Leonardo Insects must right themselves in air so as not to fall. Exactly how insects manage to right themselves via a succession of neural-motor actions is a large mystery in neural behavior of animals. The goal of our work is to find clues about their internal actions through careful measurements and analyses of their aerial acrobatics, in the case of a dragonfly. A dragonfly falling upside down can right itself in about 200ms. During this brief episode, not only it has to sense its perilous condition, it also has to respond with proper muscle actions so to modulate the flapping wing motions such that to generate enough aerodynamic torque in order to correct its orientation. Here, we measure the intricate wing modulations of all four wings that a dragonfly employs to make such a maneuver. We further develop a computational model to simulate the righting maneuver so to tease out the key wing asymmetry that leads to a successful recovery. By analyzing the falling trajectory, we calculate the muscle torque dragonfly used to drive the body rotation. We further conjecture a sensory motor pathway during the dragonfly’s righting reflex in response to the perceived horizon. [Preview Abstract] |
Sunday, November 24, 2019 4:01PM - 4:14PM |
G27.00002: Measurement of mosquito wake flow using time-resolved tomographic particle image velocimetry Zhongwang Dou, Pavlos Vlachos Recent strategies on the control of mosquito-borne diseases have been largely relying on the control of mosquito population. The flight dynamics of mosquito are closely related to their mating and courtship behavior, therefore understand the fluid dynamics can play an important role in developing novel strategies for mosquito population control. In this work, for the the first time, we measure the wake flow of a single tethered mosquito using time-resolved tomographic particle image velocimetry system. Mosquitos are tethered inside a transparent box, and fog particles are used to seed the area. Four cameras, synchronized with the illumination of a Nd: YLF laser, are employed to record the flow field at a speed of 700 Hz (frame straddling mode). The 4D flow structure, pressure field, and flow statistics at the wake of the mosquito are reconstructed and reported in this study. [Preview Abstract] |
Sunday, November 24, 2019 4:14PM - 4:27PM |
G27.00003: Measurement of starting vortex strength of a hovering hawkmoth Yun Liu From the high-speed Schlieren photography, salient flow structures were successfully visualized and captured on a near hovering hawkmoth Manduca. During the down-stroke, a vortex loop was formed with evolving size and strength. Originally, optical flow method was implemented on the Schlieren images and vortical flow field was quantified at certain time instants. However, owing to the three-dimensional nature of the flow structure and its corresponding complexities, the vortical flow field quantification is not always successful and significant uncertainties in starting vortex strength estimation exists. Therefore, in this work, a further step is taken for accurately measuring the strength of starting vortex. To achieve this goal, a time resolved 2D-PIV is conducted on a hovering hawkmoth which is feeding on an artificial flower. The high-speed Schlieren photography results, on the other hand, provide us clear guidelines about how to setup the experiment and when/where to expect the starting vortex. The flow field quantification from the conventional PIV provides us reliable vortex strength data while the high-speed Schlieren photography experiments provide us critical spatial information about the three-dimensional structure of the vortex loop. With those two temporal data quantified accurately, the instantaneous aerodynamic forces can be estimated in the end. [Preview Abstract] |
Sunday, November 24, 2019 4:27PM - 4:40PM |
G27.00004: New measure based solely on wake data for hovering performance Sachin Shinde, Jaywant Arakeri In case of hovering wherein forward speed (thus work) is zero, the conventional definition of efficiency does not hold; Figure of Merit (FM) is an alternative. However, both efficiency and FM require measurement of input power which is not trivial for hovering birds and insects. We propose a new measure, independent of measuring input power, called `jet effectiveness factor ($\Pi )$' defined based on mass, momentum and kinetic energy flux data, essentially requiring only wake velocity field which can be gathered using PIV, MTV. Inverse of $\Pi $ can be thought as efficiency. We theoretically calculate $\Pi $ for two-dimensional (2D) rectangular, triangular and Gaussian jets as 1, 1.1250 and 1.1548 respectively. Closer the value of $\Pi $ to 1, more effective would be the jet. From PIV experiments, we calculate $\Pi $ for 2D reverse Karman jet generated by flexible foil flapping in an otherwise quiescent ambient - situation relevant to hovering, and show that the value of $\Pi $ is close to that for Gaussian jet for several cases obtained by varying pitching amplitude and frequency. This new measure can be extended to calculate effectiveness of jet generated by MAVs, AUVs and cruising fish, birds, insects where measuring input power is non-trivial. [Preview Abstract] |
Sunday, November 24, 2019 4:40PM - 4:53PM |
G27.00005: ABSTRACT WITHDRAWN |
Sunday, November 24, 2019 4:53PM - 5:06PM |
G27.00006: Why are long sequences of steady flight less common at higher speeds of forward flight in Hawkmoth? Chengyu Li, Michael Corbi, Tyson Hedrick The hawkmoth is able to sustain a steady hover or level flight at lower speeds (0\textasciitilde 2 m/s). However, previous wind tunnel experiments suggested that long sequences of steady forward flight were less common at higher flying speeds (\textgreater 2.0 m/s) despite changes to the flight posture and muscle recruitment. Considering hummingbirds have about the same body size and can easily achieve \textasciitilde 10 m/s forward flight speed, it is unclear why hawkmoths were not observed achieving steady fast flight. In this work, high-speed photogrammetry and 3D surface reconstruction were used to investigate a hawkmoth's (Manduca sexta) wing kinematics at a forward flight speed of 4 m/s. The associated fluid dynamics and wing aerodynamic performance were then studied using an in-house computational fluid dynamics solver. Quantitative analysis has shown a significant amount of negative lift was generated during upstrokes at this high forward flying speed. Such a negative lift in the upstroke might reduce maximum sustained flight speeds in this species and might represent an adaptation for the hovering feeding mode for which this species is known. [Preview Abstract] |
Sunday, November 24, 2019 5:06PM - 5:19PM |
G27.00007: Effects of wing-wake interactions on the aerodynamic performances of a hovering rhinoceros beetle. Sehyeong Oh, Boogeon Lee, Hyungmin Park, Haecheon Choi We investigate the aerodynamic performance of a hovering rhinoceros beetle using numerical simulation and a quasi-steady aerodynamic model. The simulation shows that the wing-wake interactions significantly affect the aerodynamic performance. To examine the wake characteristics behind the wing, we obtain the temporal and spatial distributions of downwash motion from numerical simulation, and show that the downwash motion is non-uniform along the wing spanwise direction, of which magnitude is large immediately after the stroke reversal and small at the end of half stroke. Therefore, we model the wake behind the wing as a non-uniform (in spanwise direction) and sawtooth-type (in time) downwash motion. Also, we combine a quasi-steady aerodynamic model and a momentum theory, together with unsteady and non-uniform downwash motion. The aerodynamic performance predicted by the present aerodynamic model is in good agreement with that of the present numerical simulation. [Preview Abstract] |
Sunday, November 24, 2019 5:19PM - 5:32PM |
G27.00008: Generation of Sound from Flapping Wings of Mosquitoes Jung Hee Seo, Tyson Hedrick, Rajat Mittal It has long been recognized that mosquitoes use ``wing tones" (sound generated by flapping wings) for communication and signaling during mating. Previous experimental studies showed that the wing tone based ``communication" between conspecifics is complex, and it conveys important information about fitness and sexual interest. The mechanisms of wing tone generation and the characteristics of its sound field are however not well understood. Mosquitoes (e.g. \textit{Culex}) that employ wing-tone communication have very unique wing kinematics (high frequency and small stroke amplitude) compared to other insects of similar size and it has been speculated that this facilitated wind-tone communication. In the present study, the generation of wing-tones in a mosquito (\textit{Culex}) is computationally investigated to explore the speculation. The flow field around a hovering mosquito is simulated by solving the incompressible Navier-Stokes equations using a sharp-interface immersed boundary method, and the aeroacoustic sound is predicted by the Ffowcs Williams and Hawkings equation. The analysis of the simulation data suggests that the kinematics employed by these mosquitoes facilitates efficient generation of wing-tones. [Preview Abstract] |
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