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 X04: Ecological Fluid Mechanics II |
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Chair: Donald Webster, Georgia Institute of Technology Room: Ballroom D |
Tuesday, November 26, 2024 8:00AM - 8:13AM |
X04.00001: Structures in smells: Coupling fluid dynamic cues to odor signals in olfactory landscapes Elle Stark, Aaron C True, John P Crimaldi Animals exploit olfactory cues for survival, requiring navigation of complex odor plumes in diverse environments. As organisms navigate, they encounter a rich set of fluid dynamic cues (e.g. accelerations, strains, vorticity) alongside odor cues, owing to the coupling of the Navier-Stokes and Advection-Diffusion equations. Lagrangian coherent structures (LCS) provide an intuitive framework for investigating coupled flow and odor structure; they are derived from the flow deformation field and have been shown to drive the spatial organization and temporal evolution of scalar fields in chaotic flows. We investigate this coupled structure using 2D numerical simulations of chaotic plume dispersion with passive scalars released downstream of an array of interacting cylinder wakes. We use event-based statistics centered on whiff occurrences to quantify relative timing between flow and odor cues across plume regions and candidate flow cues. We find significant differences in relative timing across plume regions, and provide a physical interpretation based on the LCS framework and considerations of local mixing regimes. Spatial structure in relative timing variations between flow and odor cues could inform fundamental olfactory search tasks like edge detection or source localization. |
Tuesday, November 26, 2024 8:13AM - 8:26AM |
X04.00002: How does aggregation influence filtration and particle encounter in the sea anemone Metridium senile? Adetokunbo Awonusi, Arvind Santhanakrishnan Metridium senile reproduces sexually or asexually, influenced by prey availability and size in the habitat. Asexual reproduction occurs when prey is abundant and intermediately sized. This could lead to clone aggregation, which may alter the fluid dynamics within the colony, thereby impacting flow and particle transport at different colony positions. This study hypothesizes that solitary anemones may feed more than aggregated counterparts. We tested this by creating spatial configurations of an individual within an aggregation, using a live model with physical model clonemates. Flow within the live model’s tentacle crown was measured under different continuous background flow conditions to examine filtration and prey encounter chances using leakiness and Peclet number (Pe). Findings suggest solitary anemones feed more efficiently under low-flow conditions, but feeding drops as background flow speed increases. Feeding by aggregated anemones was found to significantly improve as the background flow speed was increased. Under high flow speeds, both solitary and aggregated anemones have similar feeding opportunities, though solitary ones experience significant drag. Finally, we note that Pe could serve as a potential indicator of prey selectivity among passive suspension feeders. |
Tuesday, November 26, 2024 8:26AM - 8:39AM |
X04.00003: Exploring the trade-off of lift and thrust during shrimp swimming Sara Oliveira Santos, Mageean Brown, Minki Kim, Nils Bjorn Tack, Monica M Wilhelmus Shrimp use the dynamic morphology of their pleopods to maximize net thrust and produce the necessary lift to maintain their depth in the water column while cruising. Shrimp can achieve this by cupping the distal pleopod segment, composed of the endopodite and exopodite, which induces a change in the angle of incidence (AoI) of the exopodite. The exopodite AoI enables the distribution of forces into global lift and thrust. Using a biologically inspired robotic analog based on the Pleobot, we vary the cupping angle from 0° to 80° and the biologically relevant 35°. Through Particle Image Velocimetry, direct force measurements, and a reduced-order model, we investigate the mechanisms leading to the trade-off between lift and thrust-producing forces at different cupping angles. We found that changing the cupping angle modulates lift and thrust production, and drag-based thrust forces are primarily responsible for propulsion. Further, we show that propulsive forces produced by beating pleopods can be estimated using the linear superposition of drag and inertial forces based on measured morphological parameters. Our results elucidate the mechanism by which shrimp trade-off lift and thrust, which can be leveraged in developing and designing metachronal underwater vehicles. |
Tuesday, November 26, 2024 8:39AM - 8:52AM |
X04.00004: Roles of propulsor flexibility and aspect ratio in hybrid metachronal rowing Noel M Rajive, Mitchell P Ford, Arvind Santhanakrishnan Several crustaceans with widely varying body and appendage morphologies employ a swimming strategy called hybrid metachronal rowing, where closely spaced appendages (hereafter propulsors) perform an adlocomotory metachronal power stroke followed by a nearly synchronous recovery stroke. Many species of copepods use this strategy when performing escape maneuvers. A review of published images of the swimming legs of copepods showed that the range of aspect ratio (AR; paddle length/paddle width) varied between 1<=AR<=4. In addition, appendage flexibility also can vary across species. Previous studies have shown that the interaction of propulsor tip vortices plays a considerable role in metachronal rowing performance. This work examines the effects of varying AR and propulsor flexibility on tip vortex dynamics. We conducted 2D-2C PIV and three-dimensional PTV (shake-the-box) measurements on a dynamically scaled robotic model of hybrid metachronal rowing consisting of four propulsors. The strengths of propulsor tip vortices were observed to decrease with increase in AR. Additionally, vorticity was more diffuse along the length of flexible propulsors as compared to rigid propulsors. The implications of the tip vortex dynamics on rowing performance will be discussed. |
Tuesday, November 26, 2024 8:52AM - 9:05AM |
X04.00005: Pulsating Soft Corals Shilpa Khatri, Brittany Jae Leathers, Sarah Malone, Kevin A Mitchell, Laura A Miller Soft corals of the family Xeniidae have a pulsating motion, an active energetically expensive motion by a sessile organism. We are studying how this behavior may give these corals a competitive advantage, especially by allowing their symbiotic algae to photosynthesize to a greater extent. We will present a mathematical model and computational simulations of the pulsations of the coral and the resulting mixing due to this behavior. Direct numerical simulations of the pulsating corals and the resulting fluid flow by solving the Navier-Stokes equations coupled with the immersed boundary method will be discussed. We will present results of how the mixing created by the corals is modified as we vary parameters of the fluid flow and the pulsating motion. Furthermore, we will discuss the coupling of the fluid flow with a simplified photosynthesis model and resulting simulations. |
Tuesday, November 26, 2024 9:05AM - 9:18AM |
X04.00006: Effects of bidirectional deformation on colony-scale flow around a reticulate sea fan Adetokunbo Awonusi, Jacqueline Nwamaka Esimike, Arvind Santhanakrishnan Reticulate sea fans such as Gorgonia ventalina exhibit whole colony flexibility in habitats experiencing moderate to high flow currents. The entire colony can undergo unidirectional and bidirectional deformation (oscillatory motion) depending on the environmental flow conditions. While unidirectional deformation benefits attachment by reducing drag and feeding by influencing local flow, the impact of bidirectional deformation on filtration and drag forces remains unclear. To investigate this, PIV experiments and numerical simulations were conducted on an artificial stiffened model of G. ventalina under varying oscillation parameters (angular amplitude, frequency) with and without continuous background flow. Findings suggest that bidirectional deformation induces flow recirculation and fluid displacement across the downstream and upstream sides of the colony. Increased angular amplitude results in generating more vorticity, retaining particles within the vicinity for further encounters. Vorticity production is enhanced at lower frequencies. The effect of the unsteady pressure fields on drag generation during bidirectional deformation will be presented. |
Tuesday, November 26, 2024 9:18AM - 9:31AM |
X04.00007: Measuring seawater velocity using drone imaging of jellyfish swarms Uri Shavit Tracking individual jellyfish from a fixed drone provides information about their propagation velocity, the sum of the seawater and jellyfish swimming velocities. Using the drone to measure the jellyfish swimming velocity requires, therefore, measurements of the water velocity at the time and vicinity of the jellyfish. Obtaining such measurements is challenging. Instruments such as ADVs, ADCPs, and drifters are difficult to install, release, and operate, especially when the water velocity must be measured near the jellyfish individuals. To overcome this, we propose a method, by which each jellyfish pair provides a non-intrusive measurement of the horizontal water velocity near the jellyfish. The method is based on measuring the horizontal body orientation and the propagation velocity of two jellyfish relative to the drone frame of reference. A vector summation results in a formulation of the horizontal water velocity components from which the jellyfish swimming, relative to the water frame of reference, is calculated. We have tested the accuracy of the method by computer simulations and applied it in-situ by tracking >1100 jellyfish during three campaigns near the Haifa Bay. We found that the horizontal swimming velocity of Rhopilema nomadica is 10 +/- 1 cm/s. We will present the new method, the simulation results, and the impact of the swimming velocities on the where about of jellyfish swarms. The potential implementation of the method using other swimming and flying animals will be discussed. |
Tuesday, November 26, 2024 9:31AM - 9:44AM |
X04.00008: Exploring the Effects of Changing Climates on Symbiosis Establishment in the Bobtail Squid stephen williams, Elizabeth Heath-Heckman, Erica Rutter, Shilpa Khatri Symbioses allow many organisms to overcome challenges faced in their natural environments. Rapidly changing global climates have put great strains on such symbiosis relationships. The Hawaiian Bobtail Squid Euprymna scolopes is one such organism, which has co-evolved with the bioluminescent bacteria Vibrio fischeri. Vibrio provide squid with a light-source with which they can perform counter-illumination, a process enabling the squid to camouflage itself from potential predators. Crucially, juvenile squid must be colonised by symbionts in the first hours after they hatch for this relationship to form. One key step in this process is mediated by internal fluid-structure interactions within scolopes. By utilising their respiration, ciliated surfaces, and internal geometry squid are able to process bacteria carried in these flows. Notably, this enables the selective capture of bacteria using a specialised light organ, and filters out any unwanted particles and bacteria. Using the Method of Regularised Stokeslets, and motivated by experimental observations, we have been able to simulate these flows. Furthermore, we have explored the impacts of temperature stress on the resulting flow fields as mediated by the parameters that underpin these flows. |
Tuesday, November 26, 2024 9:44AM - 9:57AM |
X04.00009: Effect of Stiffness on Batoid Undulation Bart Aron Robertus Boom, John Michael Racy, Spencer Stephen Truman, Charbel El Khoury, Tadd T Truscott, Adam Summers, Ed Habtour Batoids (e.g., stingrays, skates, mobulas) have been a source of inspiration for engineering fast, maneuverable, and highly efficient propulsion systems. In emulating batoids’ most studies often employ a high number of actuators, leading to inefficient designs. This is because those studies ignore the influence of batoids’ fin morphology in combination with their skeletal system on swimming kinematics and efficiency. This study intends to induce batoid-like kinematics with simple excitation by emulating batoid internal and external morphology. The pectoral fin models are actuated vertically at different frequencies and amplitudes in different flow regimes Re=300 and Re=4000. By recording input force, amplitude and frequency and measuring thrust, output amplitude and chord wise flow we reveal the relationships between the structural properties and the hydrodynamics. By testing oscillator and undulator species and altering their internal stiffness by changing the number of artificial radials we map the effect of stiffness and shape on both structural response (output kinematics) and fluid flow. The results suggest that the different body styles show that oscillating batoid generate more thrust at higher stiffness, however undulating batoids create more thrust with lower stiffness. Additionally, we show the different vortex structures at different Strouhal numbers. The insights into pectoral fin shape and stiffness will help us design more efficient engineered propulsive surfaces. |
Tuesday, November 26, 2024 9:57AM - 10:10AM |
X04.00010: BlueGuppy: a miniature free-swimming robot for studying hydrodynamic interaction among schooling fish Hungtang Ko, Valeria Saro-Cortes, Brian Mmari, Di Ni, Girguis Sedky, Aimy Wissa, Radhika Nagpal Schooling fish are known to take advantage of hydrodynamic interaction to save metabolic energy as they traverse the ocean. While fluid simulations and hydrofoil experiments have provided tremendous insights, it remains unclear how free-swimming fish-like swimmers interact with each other in formations. In this work, we designed a miniature fish-like robot, BlueGuppy, that can swim up to three body lengths per second. We characterize how a BlueGuppy's swimming speed increases with flapping frequency and how it turns with temporally asymmetric flapping. In addition, using PIV and force measurements, we reveal the flow field and the hydrodynamic consequences of a BlueGuppy following a leader at different relative locations. This project demonstrates the tremendous potential of free-swimming robots for revealing fluid-swarm interaction in biological collectives. |
Tuesday, November 26, 2024 10:10AM - 10:23AM |
X04.00011: TRACKING SCHOOLING FISH IN THREE DIMENSIONS Koen Muller, Jerry Westerweel, Daniel S Tam Large schools of fish are observed to execute rich patterns of collective dynamics. The three-dimensional dynamics of schooling fish is a startling display of group behavior and continues to intrigue many scientists including fluid-dynamicists. Our current understanding of the physical and social principles underlying the emergence of coordinated group motion is limited due to a lack of three-dimensional experimental data. In this work, we perform three-dimensional tracking of a school of 2000 Harengula Clupeola (false herring) in the large 3,000 cubic meter tank in the aquarium of the Rotterdam Zoo. This tank reproduces a semi-natural tropical ecosystem, in which different fish species swim and interact in a relatively unconstrained environment. Here, we present an experimental setup and a tracking approach, which allows us to track the 2000 fish in the school. We use our dataset to derive quantitative metrics to characterize the variability of the school in terms of geometry, shape, internal structure and kinematics. |
Tuesday, November 26, 2024 10:23AM - 10:36AM |
X04.00012: Wake Flow Characteristics of Rotating Beetle Wings Kiruthika Sundararajan, Gal Ribak, Roi Gurka In our efforts to advance bio-inspired flight systems, understanding the wake dynamics and aerodynamic performance is crucial. We focused on the long-horn beetle (Batocera rufomaculata), known for its enduring flight capabilities at low Reynolds number (Re~104). Our study examines fluid-structure interactions pivotal to their performance in a rotating setting akin to current quadcopter UAVs. Using Particle Image Velocimetry (PIV), we conducted flow field measurements on rotating beetle wings to explore the intricate aerodynamics of this motion. We analyzed various Angles of Attack (α) combined with rotational motion to discern their impact on flow dynamics. The near wake flow field was characterized by mean velocity field, vorticity field, Reynolds stress and Turbulent Kinetic energy. Our investigation highlights changes in momentum and energy relative to Angles of Attack (α) within a rotational frame of reference, revealing higher turbulence activity at lower angles of Attack (α). Additionally, employing numerical eduction techniques like Proper Orthogonal Decomposition (POD) and swirl ratio elucidate the formation of flow structures and their correlation with wing aerodynamics. This study offers essential insights into the intricate interplay among wing morphology, kinematics, and fluid dynamics. It aims to advance the design and optimization of rotating-wing UAV systems for enhanced performance and maneuverability across diverse environments. |
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