Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session T02: Ecological Fluid Mechanics I |
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Chair: Donald Webster, Georgia Institute of Technology Room: Ballroom B |
Monday, November 25, 2024 4:45PM - 4:58PM |
T02.00001: The swim-and-sink behavior of copepods: a revisit to mechanical power requirement and a new hypothesis on function Houshuo Jiang Many copepods display a swim-and-sink behavior, which is not energetically efficient but likely aids in perceiving and capturing diatom chains. Here, computational fluid dynamics was employed to calculate the mechanical power required by a negatively buoyant, self-propelled copepod in swim-and-sink versus hovering. The results show that upward swim-and-sink about a fixed depth always demands more power than hovering. Subsequently, high-speed microscale imaging was employed to observe the copepod Centropages sp. in swim-and-sink, specifically its encounter and handling of diatom chains for capture, along with the measured alternating swimming and sinking currents imposed by the swim-and-sink copepod. The findings suggest that during upward swimming, the copepod uses its swimming current to scan the fluid for detecting embedded diatom chains, presumably through chemoreception. Once a diatom chain is perceived, the copepod sinks and uses its sinking current to manipulate the orientation of the diatom chain before swimming upward to capture it. Overall, these results propose a hypothesis that swim-and-sink is an innate behavior that assists copepods in perceiving and maneuvering diatom chains for capture. In contrast with near-spherical algae, diatom chains predominately exhibit a horizontal orientation in the ocean, necessitating vertically oriented copepods to possess a handling behavior that maneuvers diatom chains for capture. |
Monday, November 25, 2024 4:58PM - 5:11PM |
T02.00002: 3D feeding currents of the predatory ctenophore Mnemiopsis leidyi Mitchell P Ford, Sean P Colin, John H Costello Lobate ctenophores such as Mnemiopsis leidyi are voracious predators of marine zooplankton, forming critical links in costal and oceanic food. As the global shipping industry has grown over the past century, Mnemiopsis has invaded costal waterways worldwide, unbalancing ecosystems and devastating biodiversity. Mnemiopsis is carnivorous, but not particularly picky in the prey that it consumes. The beating of cilia on the auricles generates a feeding current that is largely hydrodynamically inconspicuous to prey, drawing flow through the lobes and towards the tentillae where slow-moving or sessile prey items are captured. Prey that can perform a fast escape, such as copepods, often attempt to perform an escape after initially coming near to or contacting the lobes. However, Mnemiopsis, sensing the disturbance caused by these larger prey items, is able to close the lobes and surround the prey to prevent its escape. In this study, we present 3D velocity field data on the flows generated by Mnemiopsis during cruising and station-holding in the presence of potential prey. We show how the swimming behaviors of predator and prey can affect predation performance. |
Monday, November 25, 2024 5:11PM - 5:24PM |
T02.00003: Air-water interface deformation by impacting bioinspired cylinder arrays of varying geometry Snigdha Shiuly S Tikader, Thomas Steinmann, Jérôme Casas, Margaret L Byron Many animals have bristled appendages whose function varies depending on inter-bristle spacing, orientation, Weber number, Bond number, and Reynolds number. In a single-phase environment (e.g. water or air), such appendages may function as paddles for swimming or rakes for sensing. Some semi-aquatic insects use these appendages to facilitate takeoff from the water surface; however, the fluid mechanical interaction of the bristled appendage with the water surface is poorly understood compared to the single-phase case. We idealize the bristled appendage as a parallel array of long cylinders at equidistant spacing (ranging from 2 to 8 cylinder diameters), and experimentally investigate how such an array impacts and interacts with an air-water interface when the forces of surface tension and buoyancy are equally important (Bo~1). We also vary the geometry of the array: while each cylinder remains parallel to the undisturbed air-water interface (so that the problem is two-dimensional), we raise the outer cylinders, so that the overall array takes on a "flattened vee" shape from the side view. Using high-speed videography, we measure the deformation of the air-water interface as the array impacts the surface and infer the resulting vertical reaction force on the cylinder array. We find that by varying its geometry, the array can achieve a greater plunge depth without breaking the surface. Using computational modeling, we also explore the effects of decreasing cylinder diameter, thereby investigating the relative roles of surface tension vs. buoyancy. Our findings offer insight into the biomechanics of interfacial locomotion and open new possibilities in designing bio-inspired devices. |
Monday, November 25, 2024 5:24PM - 5:37PM |
T02.00004: Daphnia: A Master in Microfluidics J Rudi STRICKLER, Amorina Purpora, Abdessamad Talioua, Moshe Gophen, Jian Sheng Extracting particles such as live cells from a fluid, sorting those cells in a microflow, and adding small concentrations of info-chemicals to create a minute chemical landscape in the flow, are current research topics both for researchers in microfluidics and for biologists interested in the biomechanics of aquatic and marine zooplankton. Our model animal, Daphnia spp., a microcrustacean of 1 to 3 mm (about 0.12 in) size, features four pairs of appendages that are covered by the carapace. These appendages move at around 10 Hz and generate an in/out-current system to extract algae for food. |
Monday, November 25, 2024 5:37PM - 5:50PM |
T02.00005: Emergent flow asymmetries from the metachronal paddling of gossamer worm parapodia Alexander P Hoover Metachronal waves are ubiquitous in propulsive and fluid transport systems across many different scales and morphologies in the biological world. Tomopterids, or gossamer worms, are soft-bodied, holopelagic polychaetes that use metachrony with their flexible, gelatinous parapodia to deftly navigate the midwater ocean column that they inhabit. In the following study, we develop a three-dimensional, computational, fluid–structure interaction model of a tomopterid parapodium to explore the emergent metachronal waves formed from the interplay of passive body elasticity, active muscular tension, and hydro- dynamic forces. Using this fluid-structure interaction modeling framework, we will examine the role that the interplay of body elasticity, wave speed, resonance, and tension play in the resulting vortex structures and fluid transport due to their collective motion. Preliminary work will be shown including a flexible body as a base structure for the parapodia. |
Monday, November 25, 2024 5:50PM - 6:03PM |
T02.00006: Simultaneous fluid flow and active particle tracking in three dimensions during collective swimming Nina Mohebbi, Siddhartha R Shendrikar, Matthew K Fu, John O. Dabiri Hydrodynamic interactions among swimming or flying organisms can lead to complex flow patterns at the group scale. Utilizing brine shrimp (Artemia salina) as a model organism, we investigate the effects of collective movement on the fluid environment within a 20x20x24 cm measurement volume inside a larger 3000-liter tank. By leveraging the positive phototaxis of brine shrimp, we induce synchronized vertical migration. The technique, which uses a single camera and a scanning laser sheet, combines Particle Tracking Velocimetry (PTV) to track swimmers, which are 1 cm in size, and Particle Image Velocimetry (PIV) for flow measurement. This method provides a detailed analysis of the coupling between individual movements and the resulting fluid dynamics. This approach enables further investigation into collective swimming, offering new insights into collective behavior in aquatic and aerial environments. |
Monday, November 25, 2024 6:03PM - 6:16PM |
T02.00007: Propulsive Efficiency of Robotically Controlled Jellyfish for Ocean Exploration Simon R Anuszczyk, John O. Dabiri Propulsive efficiency is a limiting factor for mission duration of ocean monitoring tools. In contrast, Aurelia aurita jellyfish have a propulsive efficiency 97% lower than some underwater vehicles and are adaptable to a wide range of ocean environments. Ocean monitoring tools could potentially capitalize on jellyfish regenerative capabilities and inexpensive electronics by equipping jellyfish with microelectronic swim controllers. One key question is the physiological endurance of jellyfish for long-duration swimming. Here we experimentally investigate swimming durations commensurate with a dive to the deep ocean (e.g. greater than 6000m). While previous work found stimulated jellyfish vertical swimming speeds of up to 4.5 times baseline speeds without swim controllers, propulsive efficiency during free-swimming experiments has not been measured. We utilize a 6-meter tall water tank treadmill to characterize jellyfish swimming endurance and performance experimentally. This apparatus uses computer vision to provide a flow current that opposes the animal and enables continuous swimming without encountering the vertical limits of the tank. Swimming efficiency is inferred from oxygen consumption and measurements of changes in body mass. These experiments inform an analytical model of stimulated jellyfish swimming dynamics and predict performance of jellyfish of different geometries. |
Monday, November 25, 2024 6:16PM - 6:29PM |
T02.00008: The Kinematics and Flight Behaviors of Fruit Flies and Fungus Gnats in a Vertical Wind Tunnel Evan Joseph Williams, Ignazio Maria Viola, Laura Ross, Robert Baird, David W Murphy Insects utilize atmospheric flows for long range migration and dispersal. As these beneficial flows are located several kilometers above the ground, tiny insects must use convective upwellings as a transport mechanism to reach them. However, insect flight behaviors and mechanisms in these vertical upwellings are not well understood, prompting questions about how tiny insects control their flight in vertical flows. Here we investigate the flight behavior of two tiny insect species, the 3 mm fruit fly (Drosophila melanogaster) and the 2 mm fungus gnat (Lycoriella ingenua), while exposed to quiescent air and to a steady 0.5 m/s upwards flow (characterized via PIV) within a vertical wind tunnel. We use high-speed 3D photogrammetry, recording at 300 Hz (106 events) and 4700 Hz (43 events) at different magnifications, to capture flight trajectories and wingbeat kinematics, respectively. In the upwards flow as compared to quiescent air, both species exhibited an increased body pitching frequency, likely in an effort to maintain stability. With flow, flight trajectory sinuosity increased for the smaller, more weakly flying fungus gnats but decreased for the larger, stronger fruit flies. These results provide insight into how tiny insects may adapt their flight to a convective upwelling. |
Monday, November 25, 2024 6:29PM - 6:42PM |
T02.00009: The effects of macro- & micro-scale morphology on drag and odor capture around honey bee antennae Derek John Goulet, Aaron C True, Brian H Smith, John P Crimaldi Insects explore environments using chemoreceptors on their antennae. Antennae exhibit diverse morphologies at both the macro-scale (antennal lengths, diameters, and structure) and micro-scale (pore plates and hairs). Presently, we focus on understanding the effect of these morphologies on odor capture efficiency (ratio of odor reaching binding sites to supplied odor) and fluid drag forces for a model organism, the honey bee. We built numerical models of honey bee antennae in representative flows transporting a uniform odor field, resolving three-dimensional flow and odor fields around the antenna. We evaluated effects of Reynolds number (a function of wind speed and antennal diameter) and pore packing density (ratio of pore plate diameter to distance between pores) on capture efficiencies. Increasing Reynolds number increases viscous stresses (predominant contribution to drag) and diminishes the relative strength of diffusive fluxes to the antennal surface (primary mechanism of capture efficiency). Increasing pore packing density does not change viscous stresses but allows more odor to reach binding sites (increasing capture efficiency) asymptotically, driven by competition between adjacent pores. This suggests an optimal spatial configuration of odor binding sites on a given antennal surface area within a uniform odor field. Future efforts will explore unsteadiness in the flow and odor fields and additional macro- and micro-scale effects on drag and odor capture. |
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