Flow Induced by Collective Vertical Migration: Impact of Swimmer Distribution, Buoyancy, and Wake Interactions
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| Publicado en: | ProQuest Dissertations and Theses (2025) |
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ProQuest Dissertations & Theses
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| Acceso en línea: | Citation/Abstract Full Text - PDF Full text outside of ProQuest |
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| Resumen: | Various animal species exhibit collective motion, characterized by coordinated movement within groups of organisms. A prominent oceanic example is diel vertical migration (DVM), wherein zooplankton migrate vertically from deeper waters during the day to shallower regions at night, often covering distances of approximately 1 kilometer. Despite numerous field measurements, laboratory observations, and theoretical studies of biogenic mixing resulting from collective swimming, the scale of fluid mixing induced by DVM remains unresolved. A key challenge is linking the behavior and flows created by large numbers of individual organisms to collective-scale fluid dynamics. Since most swimmers involved in DVM operate at intermediate Reynolds numbers, the dynamics of these systems are nonlinear and span a wide range of spatial and temporal scales.This thesis investigates the scaling of flows generated by vertical migration of brine shrimp (Artemia salina) aggregates and parameterizes them through a combination of laboratory measurements and semi-analytical modeling. First, a volumetric, laser scanning system measured swimmer behaviors and flow interactions during vertical migrations induced in a laboratory setting. Swimmers demonstrated consistent vertical swimming velocities in varying environmental conditions and exhibited a Gaussian distribution within the tank cross-section while displaying a tendency to move inward toward the center of the tank, where illumination was brightest. A scaling relationship between swimmer buoyancy, ascent speeds, and the resulting flow speed was developed to contextualize these results. Finally, a semi-analytical model was developed to estimate the flow generated by the wakes of multiple swimmers in proximity. The behaviors of individual swimmers were informed by the empirical results of the previous section and superposed using an iterative method that conserves mass and momentum to solve for the aggregation-scale flow. Numerical results suggested that the induced flow upstream in the aggregation was insensitive to the presence of downstream swimmers, the average flow speed tended to reach a plateau beyond a threshold aggregation length, and that closer swimmer spacing led to higher induced flow speeds. |
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| ISBN: | 9798290652504 |
| DOI: | 10.7907/hz5j-g795 |
| Fuente: | Publicly Available Content Database |