Individual-environment interactions in swimming: The smallest unit for analysing the emergence of coordination dynamics in performance?

Displacement in competitive swimming is highly dependent on fluid characteristics, since athletes use these properties to propel themselves. It is essential for sport scientists and practitioners to clearly identify the interactions that emerge between each individual swimmer and properties of an aquatic environment. Traditionally, the two protagonists in these interactions have been studied separately. Determining the impact of each swimmer’s movements on fluid flow, and vice versa, is a major challenge. Classic biomechanical research approaches have focused on swimmers’ actions, decomposing stroke characteristics for analysis, without exploring perturbations to fluid flows. Conversely, fluid mechanics research has sought to record fluid behaviours, isolated from the constraints of competitive swimming environments (e.g. analyses in two-dimensions, fluid flows passively studied on mannequins or robot effectors). With improvements in technology, however, recent investigations have focused on the emergent circular couplings between swimmers’ movements and fluid dynamics. Here, we provide insights into concepts and tools that can explain these on-going dynamical interactions in competitive swimming within the theoretical framework of ecological dynamics

Form, function and flow in the plankton : jet propulsion and filtration by pelagic tunicates

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2010Trade-offs between filtration rate and swimming performance among several salp species with distinct morphologies and swimming styles were compared. Small-scale particle encounter at the salp filtering apparatus was also explored. Observations and experiments were conducted at the Liquid Jungle Lab, off the pacific coast of Panama in January 2006 through 2009. First, time-varying body volume was calculated by digitizing salp outlines from in situ video sequences. The resulting volume flow rates were higher than previous measurements, setting an upper limit on filtration capacity. Though each species possessed a unique combination of body kinematics, normalized filtration rates were comparable across species, with the exception of significantly higher rates in Weelia cylindrica aggregates, suggesting a tendency towards a flow optimum. Secondly, a combination of in situ dye visualization and particle image velocimetry (PIV) measurements were used to describe properties of the jet wake and swimming performance variables including thrust, drag and propulsive efficiency. All species investigated swam via vortex ring propulsion. Though Weelia cylindrica was the fastest swimmer, Pegea confoederata was the most efficient, producing the highest weight-specific thrust and whole-cycle propulsive efficiency. Weak swimming performance parameters in Cyclosalpa affinis, including low weight-specific thrust and low propulsive efficiency, may be compensated by comparatively low energetic requirements. Finally, a low Reynolds number mathematical model using accurately measured parameters and realistic oceanic particle size concentrations showed that submicron particles are encountered at higher rates than larger particles. Results from feeding experiments with 0.5, 1 and 3 μm polystyrene microspheres corroborated model predictions. Though 1 to 10 μm-sized particles (e.g. flagellates, small diatoms) are predicted to provide four times as much carbon as 0.1 to 1 μm- sized particles (e.g. bacteria, Prochlorococcus), particles smaller than the mesh size (1.4 μm) can still fully satisfy salp energetic needs.Funding to support my thesis research, tuition and stipend primarily came from two NSF grants (OPP-0338290 and OCE-0647723). I also received support from the WHOI Academic Programs Office in the form of a Fye teaching fellowship, an Ocean Ventures Fund award and assistance with tuition and travel to meetings and two summer courses. I received funds from MIT, WHOI Biology Department and Friday Harbor Labs for travel and tuition for a summer course at Friday Harbor Labs. Further research support came from the WHOI Ocean Life Institute and the Journal of Experimental Biology

Jet propulsion and filtration by pelagic tunicates

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 91-99).Trade-offs between filtration rate and swimming performance among several salp species with distinct morphologies and swimming styles were compared. Small-scale particle encounter at the salp filtering apparatus was also explored. Observations and experiments were conducted at the Liquid Jungle Lab, off the pacific coast of Panama in January 2006 through 2009. First, time-varying body volume was calculated by digitizing salp outlines from in situ video sequences. The resulting volume flow rates were higher than previous measurements, setting an upper limit on filtration capacity. Though each species possessed a unique combination of body kinematics, normalized filtration rates were comparable across species, with the exception of significantly higher rates in Weelia cylindrica aggregates, suggesting a tendency towards a flow optimum. Secondly, a combination of in situ dye visualization and particle image velocimetry (PIV) measurements were used to describe properties of the jet wake and swimming performance variables including thrust, drag and propulsive efficiency. All species investigated swam via vortex ring propulsion. Though Weelia cylindrica was the fastest swimmer, Pegea confoederata was the most efficient, producing the highest weight-specific thrust and wholecycle propulsive efficiency. Weak swimming performance parameters in Cyclosalpa afinis, including low weight-specific thrust and low propulsive efficiency, may be compensated by comparatively low energetic requirements.(cont.) Finally, a low Reynolds number mathematical model using accurately measured parameters and realistic oceanic particle size concentrations showed that submicron particles are encountered at higher rates than larger particles. Results from feeding experiments with 0.5, 1 and 3 [mu]m po- lystyrene microspheres corroborated model predictions. Though 1 to 10 pm-sized particles (e.g. flagellates, small diatoms) are predicted to provide four times as much carbon as 0.1 to 1 pm- sized particles (e.g. bacteria, Prochlorococcus), particles smaller than the mesh size (1.4 [mu]m) can still fully satisfy salp energetic needs.by Kelly Rakow Sutherland.Ph.D

Marine macroinvertebrates as indicators to assess the effects of Marine Protected Areas on temperate rocky reefs

Tese de mestrado, Ecologia Marinha, Universidade de Lisboa, Faculdade de Ciências, 2021The increasing degradation of marine coastal habitats due to many types of anthropogenic pressures (e.g. overfishing, water pollution, underwater tourism, etc.), led governments and intergovernmental organizations to create directives and regulations for the protection of marine ecosystems (e.g. Marine Strategy Framework Directive) and establish Marine Protected Areas (MPA), which are now widely accepted as adequate tools to protect, maintain, and restore marine ecosystems. However, in order to well manage their effectiveness, periodic monitoring is required. Biological indicators are typically used to access the protection effect of a MPA. Nevertheless, for temperate marine subtidal rocky reefs, most of these indicators are based on fish and commercial invertebrates’ traits, whereas for the overall invertebrates’ assemblages, information is lacking. Therefore, the present study assessed the taxonomic and functional response of invertebrate assemblages to the protection effect of the Arrábida Marine Protected Area (Portugal), in order to define specific traits, useful to be used as biological indicators. The combined results of PERMANOVA and discriminant analyses showed an overall strong environmental gradient along the MPA, revealing an already expected situation of multiple stressors (natural and anthropogenic) influencing the local invertebrate communities. This environmental gradient is evident and seemed capable of weakening protection effects. Nevertheless, some potentially good biological indicators of protection effects were detected, namely “density of high value species”, “density of bycatch species with high value”, “densities of scavengers and omnivores” and “densities of grazers and herbivores” showed responsive trends to fishing pressure; Bryozoa and Gorgoniidae taxa showed responsive trends to diving pressure, even though no functional trait responded significantly to this pressure. Although most of these trends could not provide clear insights, this study improves the understanding of rocky reefs invertebrate assemblage’s response to protection effect and their potential use as biological indicators of anthropogenic pressures, contributing to the future development of environmental assessment tools.O aumento da degradação dos habitats marinhos costeiros, como consequência de diversos tipos de pressões antropogénicas (ex.: excesso de pesca, poluição da água, turismo subaquático, etc.), levou a que os governos e organizações intergovernamentais criassem diretivas e regulamentos para proteger os ecossistemas marinhos (ex.: Diretiva Quadro Estratégia Marinha) e estabelecessem Áreas Marinhas Protegidas (AMP), que são atualmente consideradas uma ferramenta adequada para a manutenção e recuperação de ecossistemas marinhos. Contudo, para uma gestão eficiente, são necessárias monitorizações periódicas, nas quais são frequentemente utilizados indicadores biológicos, que suportem a avaliação do efeito de proteção de uma AMP. No entanto, para os recifes rochosos de zonas temperadas, a maior parte destes indicadores são atualmente baseados em grupos funcionais de peixes e invertebrados com valor comercial, enquanto que os restantes grupos de invertebrados são pouco representados devido à falta de informações. Por isso, neste estudo foi avaliada a resposta destes grupos ao efeito de proteção da Área Marítima Protegida da Arrábida (Portugal), de modo a definir grupos funcionais específicos, úteis como indicadores biológicos. Os resultados da PERMANOVA e das análises discriminantes mostraram um forte gradiente ambiental ao longo da AMP, revelando uma situação já esperada de vários fatores de stress (naturais e antropogénicos) que influenciam as comunidades de invertebrados locais. Este gradiente ambiental tornou difícil a identificação clara de eventuais efeitos da proteção nas comunidades de invertebrados. No entanto, foram detetadas algumas tendências que sinalizam potenciais indicadores biológicos, nomeadamente a “densidade de espécies com alto valor comercial”, a “densidade de espécies acessórias com elevado valor comercial” , as “densidades de necrófagos e omnívoros”, e ainda as “densidades de raspadores e herbívoros” revelaram tendências de resposta à pressão de pesca, e apesar de nenhum grupo funcional ter respondido significativamente à pressão da atividade de mergulho recreativo, os taxa Bryozoa e Gorgoniidae mostraram capacidade de resposta a esta pressão. Embora, a maioria destas tendências sejam fracas e não providenciem uma resposta clara, (pelo que estudos adicionais sobre a sensibilidade destes indicadores são necessários), este estudo contribui para uma melhor compreensão da resposta das comunidades de invertebrados de recifes rochosos ao efeito de proteção, e o seu potencial uso como indicador biológico dos efeitos antropogénicos, contribuindo para o futuro desenvolvimento de ferramentas de avaliação ambiental

Aerodynamics of Track Cycling

The aim of this thesis was to identify ways in which the velocity of a track cyclist could be increased, primarily through the reduction of aerodynamic drag, and to determine which factors had the most significant impact on athlete performance. An appropriate test method was set up in the wind tunnel at the University of Canterbury to measure the aerodynamic drag of different cycling positions and equipment, including helmets, skinsuits, frames and wheels, in order to measure the impact of specific changes on athlete performance. A mathematical model of the Individual Pursuit (IP) event was also created to calculate the velocity profile and finishing time for athletes competing under different race conditions. The model was created in Microsoft Excel and used first principles to analyse the forces acting on a cyclist, which lead to the development of equations for power supply and demand. The mathematical model was validated using SRM data for eleven, elite track cyclists, and was found to be accurate to 0.31s (0.16%). An analysis of changes made to the bike, athlete, and environmental conditions using the mathematical model showed that the drag area and air density had the greatest impact on the finishing time. The model was then used to predict the finishing times for different pacing strategies by generating different power profiles for a given athlete with a fixed stock of energy (the work done remained the same for all generated power profiles) in order to identify the optimal pacing strategy for the IP. The length of time spent in the initial acceleration phase was found to have a significant impact on the results, although all strategies simulated with an initial acceleration phase resulted in a faster finishing time than all other strategies simulated. Results from the wind tunnel tests showed that, in general, changes made to the position of the cyclist had the greatest impact on the aerodynamic drag compared to changes made to the equipment. Multiple changes in position had a greater impact on drag than individual changes in position, but the changes were not additive; the total gain or loss in drag for multiple changes in position was not the sum of individual gains or losses in drag. Actual gains and losses also varied significantly between athletes, primarily due to differences in body size and shape, riding experience, and reference position from which changes were made from. Changes in position that resulted in a reduction of the frontal area, such as lowering the handlebars and head, were the most successful at reducing the aerodynamic drag, and a change in skinsuit was found to have the greatest impact on drag out of all equipment changes, primarily due to the choice of material and seam placement. The mathematical model was used to quantify the impact of changes in position and equipment made in the wind tunnel on the overall finishing time for a given athlete competing in an IP event. Time savings of up to 8 seconds were seen for multiple changes in position, and up to 5 seconds for changes to the equipment. Overall this thesis highlights the significance of aerodynamics on athlete performance in track cycling, suggesting that it is worthwhile spending time and money on research and technology to find new ways to reduce the aerodynamic drag and maximise the speed of cyclists. Although this thesis primarily concentrates on the Individual Pursuit event in track cycling, the same principles can be applied to other cycling disciplines, as well as to other sports

Numerical modeling of thermal bar and stratification pattern in Lake Ontario using the EFDC model

Thermal bar is an important phenomenon in large, temperate lakes like Lake Ontario. Spring thermal bar formation reduces horizontal mixing, which in turn, inhibits the exchange of nutrients. Evolution of the spring thermal bar through Lake Ontario is simulated using the 3D hydrodynamic model Environmental Fluid Dynamics Code (EFDC). The model is forced with the hourly meteorological data from weather stations around the lake, flow data for Niagara and St. Lawrence rivers, and lake bathymetry. The simulation is performed from April to July, 2011; on a 2-km grid. The numerical model has been calibrated by specifying: appropriate initial temperature and solar radiation attenuation coefficients. The existing evaporation algorithm in EFDC is updated to modified mass transfer approach to ensure correct simulation of evaporation rate and latent heatflux. Reasonable values for mixing coefficients are specified based on sensitivity analyses. The model simulates overall surface temperature profiles well (RMSEs between 1-2°C). The vertical temperature profiles during the lake mixed phase are captured well (RMSEs < 0.5°C), indicating that the model sufficiently replicates the thermal bar evolution process. An update of vertical mixing coefficients is under investigation to improve the summer thermal stratification pattern. Keywords: Hydrodynamics, Thermal BAR, Lake Ontario, GIS

Bowdoin Orient v.135, no.1-25 (2005-2006)

https://digitalcommons.bowdoin.edu/bowdoinorient-2000s/1006/thumbnail.jp