Bulletin of the American Physical Society
74th Annual Meeting of the APS Division of Fluid Dynamics
Volume 66, Number 17
Sunday–Tuesday, November 21–23, 2021; Phoenix Convention Center, Phoenix, Arizona
Session P13: Biological Fluid Dynamics: Flying Insects |
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Chair: David Murphy, University of South Florida Room: North 127 ABC |
Monday, November 22, 2021 4:05PM - 4:18PM |
P13.00001: Micro-PIV Measurements of a Tiny Insect Performing Clap and Fling Evan J Williams, David W Murphy Tiny sub-millimeter insects in flight use the clap and fling mechanism to generate lift, but the aerodynamics of this mechanism are not well understood owing to the small spatial and fast temporal scales involved and the difficulty of experimentally observing the flow around the insect’s wings. To examine tiny insect flight, we implemented a novel ultra-high speed brightfield micro PIV system to measure time-resolved (10 kHz) flows generated by a freely flying sweet potato whitefly (Bemisia tabaci). An orthogonally placed and time synchronized camera was used to implement 3D stereophotogrammetry that was calibrated via direct linear transformation to determine the insect’s position in the PIV measurement plane, provide flow visualization, and measure body and wing kinematics. The whitefly, which has two pairs of high aspect ratio wings, has a body length of 0.8 mm, forewing length of 0.9 mm, hindwing length of 0.75 mm, stroke amplitude of 123○, beat frequency of 150 Hz, and a chordwise Reynolds number of 14. We present time-resolved flow fields of the clap and fling, which reveals a downwards jet ejected from between the wings with flow speeds up to 400 mm/s during clap and a medial spanwise flow during the fling as the wings create a V-shaped gap. |
Monday, November 22, 2021 4:18PM - 4:31PM |
P13.00002: Experimental and Computational Investigation of the Aero-Acoustics of Flying Beetles John S Allen, Rintaro Hayashi, Kevin O'Rourke The sounds of flapping wing insects are typically dominated by a fundamental with higher harmonics, but the underlying structure and aero-acoustics beyond the frequency and amplitude are not well understood especially for beetles. However, the aerodynamics and acoustics of invasive species of beetles are of interest in terms of fundamentals of flight and passive detection methods. The Coconut Rhinoceros Beetle (Oryctes rhinoceros) and the Oriental Flower Beetle (Protaetia orientalis) have been studied during tethered flight with synchronized microphone array measurements and high speed videos (1000-10,000 fps). The larger Coconut Rhinoceros Beetles have fundamental ~ 50 Hz with a distinctive torsional wing rotation compared that of the Oriental Flower Beetle (~100 Hz). Computational fluid dynamics simulations were performed using an unsteady compressible flow solver (CAESIM, from Adaptive Research) using a high resolution (TVD) methodology. Models of the wing flapping motion were accomplished using mesh deformation techniques with the flapping following from rotation with a prescribed bending, coupled rotation and an originating translation from the wing’s hinge position. Fluid structure interaction simulations, with respect to the wing’s flexibility, are planned for an extended experimental comparison. |
Monday, November 22, 2021 4:31PM - 4:44PM Not Participating |
P13.00003: Sub-laminar drag reduction over butterfly inspired grooves due to the roller-bearing effect Amy W Lang, Sashank Gautam, Leonardo M Santos It has long been thought that the scales found on butterfly wings perform an aerodynamic function. A motion capture flight test study of live Monarch specimens revealed that removing the scales covering their wings reduced their flight efficiency (measured as Joules per flap) by 38%. One possible function of the scales is to reduce the skin friction of the air passing over their wings through the microscopic grooves found within the roof-shingle pattern formed by the scales. Tow tank studies were performed to measure the flow over butterfly inspired grooved geometries embedded in a flat plate which confirmed the formation of trapped embedded vortices within the cavities that resulted in sub-laminar surface drag due to the roller-bearing effect. In other words, at low enough Re (Re below 100 based on cavity depth) stable vortices form in the grooves that allow the outer boundary layer flow to pass over the grooved surface with lower drag due to the partial slip condition when passing over the embedded cavity vortices. Various geometries were tested based on the butterfly scale geometry. The highest drag reduction measured 26.3% over grooves with a 45 degree wall angle and 2:1 aspect ratio at a Re of 8.5, which is dynamically similar to the flow over butterfly wings. |
Monday, November 22, 2021 4:44PM - 4:57PM |
P13.00004: Circulatory flow patterns in a dragonfly wing elucidated from a microfluidic model Sangjin Ryu, Haipeng Zhang, Mary Salcedo, John J Socha, Günther Pass Insect wings consist of a network of tubular veins and thin inter-connected membrane. Within these veins are hemolymph (blood), tracheal branches (oxygen delivery), and nerves connected to vital sensory organs on the wing. Since blood flow supplies water and nutrients to the sensory organs and other tissues and removes waste products, veins and hemolymph flow are crucial for stability, flexibility, and functionality of the delicate wing blade. However, the relationship of wing venation on hemolymph circulation remains poorly studied. Previous experiments tracking hemocytes (blood cells) in transparent veins of living specimen gave some insight into some flow patterns. To investigate detailed hemodynamics in complex wing venation, we used photo/soft-lithography to create a microfluidic wing vein model of the dragonfly, Anax junius. Blood flow was simulated by injecting dyed water into the veins using a range of flow velocities and input locations. Microbeads were used to characterize local flow patterns within the veins. Visualized flow patterns suggested that advection dominates near the wing base, whereas diffusion dominates toward the wing tip. Biomimetic wing vein devices allow for further investigation into the insect wing’s unique circulatory system and transport phenomena. |
Monday, November 22, 2021 4:57PM - 5:10PM Not Participating |
P13.00005: Fluid Filled Flapper: Modeling hemolymph circulation in a microfluidic insect wing replica Afreen E Khoja, Mary Salcedo, Sevak Tahmasian, John J Socha, Anne Staples Insect wings bend, twist, and deform during flapping flight. The insect’s circulatory system is made up of thin membranes and tubular veins. Respiratory organs, called trachea, extend into the veins creating a circuit of liquid and air flow in the wing. Distribution of hemolymph (insect blood) is needed for wing hydration and flexibility, sustaining living organs in the wing, and supplying active mechanosensing during flapping. Although insects possess a specific thoracic pump employed for driving hemolymph flow in the wing, the flapping frequency during flight (20-500 Hz) is much higher than that of pumping (1-3 Hz). How the nominally creeping (Re = 0.1) hemolymph flows in the wing are influenced by this high frequency flapping during flight is unknown. Using the North American grasshopper (Schistocerca americana), a dynamic flier with a complex wing vein network, we built a microfluidic flapping wing model to test hypotheses that flapping motions influence hemolymph circulation in a wing. The flapper was scaled up by a factor of 2.4x with a flow channel design that maintains dynamic similarity (Re = 0.1, Wo = 1.88), and printed using a stereolithography FormLabs Form 3 printer. The channels were seeded with dye droplets and microbeads in two separate experiments, sealed, attached to a sinusoidal oscillator, and then flapped at 3.45 Hz. Fluid movement was visualized in the channels using a high-speed camera (Photron Mini UX100) and analyzed using image processing (FIJI, ImageJ). The experiments confirmed that flapping does influence hemolymph circulation in the wing. |
Monday, November 22, 2021 5:10PM - 5:23PM |
P13.00006: Effects of wing-induced flow on the odor plume structures in an upwind surging flight of monarch butterfly Zhipeng Lou, Menglong Lei, Haibo Dong, Kai Zhao, Chengyu Li Butterflies rely on their olfaction to sense the odors emitted from nectar. During the odor tracking flight, flapping wings have been speculated to actively draw odor plumes to the antennae, an action analogous to “sniffing” in mammals. Observations have long indicated that wing beating is a critical part of active olfactory sampling for butterflies, while limited studies have been carried out to evaluate how the body and wing kinematics perturb the odor plumes structures and impact the mass transport of odorant to the antennae. In this study, we reconstructed both body and wings kinematics of a forward flying monarch butterfly’s (Danaus plexippus) based on high-speed images. Computational Fluid Dynamics (CFD) simulations were adopted here as a non-intrusive approach to investigate the unsteady flow field and odorant transport process by solving the Navier-Stokes and the advection-diffusion equations. Our results showed that the flapping motion enhanced the peak odor intensity around its antennae by approximately five times. In addition, the flapping motion extended the duration of peak odor intensity attachment near the head. A longer peak period potentially provides the butterfly with more time to process odor information. |
Monday, November 22, 2021 5:23PM - 5:36PM Not Participating |
P13.00007: The effect of bio-inspired butterfly wing tip scales on the growth of a leading edge vortex Julia Barefoot, Amy W Lang, Sashank Gautam Previous studies with live Monarch butterflies have shown that removal of the scales can have a large effect on flight efficiency. One potential mechanism is if the scales found on the wing tips can affect tip-vortex growth. This study investigates the effect of butterfly wing tip scales on leading edge vortex (LEV) formation and growth. It is hypothesized that the addition of wing tip scales will decrease the vortex growth as the scales impede the motion of the flow around the tip of the wing. This would result in less energy loss to the tip vortices occurring during butterfly flight. A tow tank experiment was used to replicate the butterfly wing tip scales' effect through the movement of two plates in mineral oil. The first model is a smooth-edged flat plate while the other has 3D printed scales covering the leading edge which mimic the long, thin scales found on the wing tips of the Monarch butterfly. Digital Particle Image Velocimetry (DPIV) was then used to track the development of LEVs. Results will be presented. |
Monday, November 22, 2021 5:36PM - 5:49PM |
P13.00008: Wing Flexabilty impacts LEV Bursting location on hawkmoth wings Marc A Guasch, Megan Matthews, Alexander Gehrke, Karen Mulleners, Simon Sponberg Flapping flight involves a variety of phenomena that allow centimeter scale aviation. These phenomena act on both the flapping wing and environment in complex ways. In the hawkmoth (Manduca sexta) vortices develop along the leading edge of the wing which allows for an increase in lift; however, as this leading-edge vortex (LEV) gets further from the root, the LEV can destabilize, losing its quasi-stable circulation and becoming disordered in a process known as bursting. Here we show how aging effects the flexibility, and shape of hawkmoth wings, impacting flow dynamics and leading to an earlier bursting of LEVs along the span. By measuring the flexural stiffness (EI) and digitally capturing the deformation of a mounted hawkmoth wing, we show how aging decreases wing flexibility and causes irregular shape change. Additionally, by comparing smoke visualization of mounted wings, we find that aging effects shifts the transition point of bursting along the spanwise direction by about 10%. Further experiments utilizing rigid 3D printed wings quantify the impact of shape on force production and circulation along the wings. Our results show how aging acts as an aerodynamic inhibitor in the stability of leading-edge vortices, and suggest that changes in flexibility and shape due to aging may be a key factor in LEV stability. |
Monday, November 22, 2021 5:49PM - 6:02PM |
P13.00009: Unsteady lift generation of corrugated wing by lambda vortex collapse Yusuke Fujita, Makoto Iima Dragonfly wing is not smooth but corrugated; its vertical cross-section consists of connected series of line segments. Some previous studies suggest that the aerodynamic performance of the corrugated wing is higher than that of the flat wing at the low Reynolds numbers (Re \simeq O(10^3)). However, the details are not fully investigated. In particular, the aerodynamic characteristics and flow property during unsteady wing motion has not been studied in detail because of the complicated flow characteristics. |
Monday, November 22, 2021 6:02PM - 6:15PM |
P13.00010: Search strategies in a turbulent flow using a POMDP framework Robin Heinonen, Luca Biferale, Antonio Celani, Massimo Vergassola When searching for a distant food source, an insect (such as a moth or mosquito) generally cannot rely on chemotactic strategies which climb the concentration gradient of an emitted cue (such as heat, carbon dioxide, or an odor). On the macroscopic scales of interest, turbulence mixes the cue into patches of relatively high concentration over a background of very low concentration, so that the insect will only detect the cue intermittently. In the face of such limited information, locating the source becomes a nontrivial problem. In this work, we cast this search problem in the language of a partially observable Markov decision process and compute strategies that are near-optimal with respect to the arrival time. The trajectories and arrival time pdfs associated with these near-optimal strategies are compared with those associated with a number of heuristic strategies. |
Monday, November 22, 2021 6:15PM - 6:28PM |
P13.00011: Gust responses in flying insects: Insights into their kinematic response and recovery strategies Dipendra Gupta, Jaywant H Arakeri, Sanjay P Sane Although large aircraft can fly in all sorts of turbulent wind conditions, smaller crafts such as micro air vehicles (MAVs) are more susceptible to ambient fluctuations in wind speed and, therefore, more difficult to control. MAVs are inspired by insects that can stabilize themselves rapidly when perturbed by natural gusts, yet there are few studies that directly address the gust responses of either flying insects or small crafts. Here, we investigated the flight of freely flying black soldier flies subjected to a discrete head-on aerodynamic gust in the form of a repeatable vortex ring generated under controlled laboratory conditions. We recorded their flight motion using two high-speed cameras and analyzed body and wing kinematics in 14 trials. Our aim was to characterize various flight parameters that insects control when they encounter these abrupt gusts. Under these conditions, the body roll angles of insects typically undergo a large change in about 2 wing beats (WB) (~20 ms). The insect recovers from these perturbations in about 9 WB. This roll is countered by the insect with highly asymmetric wing stroke amplitudes, presumably to generate the necessary counter torques. They are also accompanied by changes in pitch-down attitude and flight deceleration. From these readings, we can gain insights into how the flapping insects become unstable and how they recover their stability through passive and active mechanisms. |
Monday, November 22, 2021 6:28PM - 6:41PM |
P13.00012: Adaptive numerical simulations of insect flight using wavelet techniques Thomas Engels, Dmitry Kolomenskiy, Kai Schneider We present a wavelet-based adaptive approach to compute the aerodynamics of flapping insects. Dynamically evolving grids using regular Cartesian blocks allow significant reduction of memory and CPU time requirements while monitoring the precision of the computation. Distributing the blocks among MPI processes permits an efficient parallelization on large scale supercomputers. The numerical approximation uses artificial compressibility to avoid solving elliptic problems and volume penalization is applied to impose boundary conditions on the Cartesian grids. A centered 4th-order finite difference discretization is combined with biorthogonal interpolating wavelets as grid refinement indicators. Different validation cases are presented to assess the accuracy and performance of the open access code WABBIT on massively parallel computer architectures (Engels et al., Commun. Comput. Phys., doi:10.4208/cicp.OA-2020-0246). Flow simulations of flapping insects demonstrate its applicability to complex, bio-inspired problems. First computations using realistic fly bodies obtained from mirco-CT scans are likewise presented. |
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