Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 55, Number 16
Sunday–Tuesday, November 21–23, 2010; Long Beach, California
Session RS: Biofluids: General |
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Chair: Dimitrios Papavassiliou, University of Oklahoma Room: Long Beach Convention Center Grand Ballroom A |
Tuesday, November 23, 2010 3:05PM - 3:18PM |
RS.00001: Rolling up with the flow to reduce drag: A numerical and experimental study inspired by leaves Laura Miller, Christina Hamlet, Arvind Santhanakrishnan Flexible plants, fungi, and sessile animals reconfigure in wind and water to reduce the drag forces acting upon them. In strong winds and floodwaters, leaves roll up into cone shapes that reduce drag compared to rigid objects of similar surface area. Less understood is how a leaf attached to a flexible petiole (leafstalk) will roll-up stably in an unsteady flow. A combination of experiments and numerical simulation is used to describe the unsteady forces acting on flexible sheets attached to flexible beams. These flexible structures oscillate in steady and unsteady flow, and average drag forces are higher than those previously reported for flexible beams and sheets tethered to a rigid point. One important distinction between these models and the actual leaves is the ability to roll up into three-dimensional cone shapes. The experiments were repeated for flexible disks cut along a radius rather than rectangular sheets. The sheets reconfigured into stable cone shapes similar to leaves. [Preview Abstract] |
Tuesday, November 23, 2010 3:18PM - 3:31PM |
RS.00002: Flow characterization in vegetated marsh environments Jenahvive Morgan, Aline Cotel, Paul Webb The evaluation of wake flows due to aquatic vegetation is necessary to understand the response of the environment to flow through a marsh. Considering the influence of vegetation on the turbulent characteristics of the flow is important in understanding its effect on the surrounding environment and can be applied to the design and creation of artificial marsh environments for restoration projects. Vegetative environments, due to their structure, create turbulence in the flow which in turn affects the response of the native fish species, as well as contaminant and sediment transport. In an effort to model an aquatic vegetative environment, arrays of vertically aligned cylinders of diameter equal to 1/4" were set-up in staggered positions to create a variety of flow configurations in a re-circulating water tunnel. Particle Image Velocimetry (PIV) was used to determine flow characteristics at different velocities for each geometry. In particular, turbulence downstream of the cylinders was examined for different arrangements of the marsh model. The data reveal a strong relationship between the arrangement of the cylinder arrays and the wake turbulence downstream of the cylinders. These results have implications for fish responses to aquatic environment and the design of artificial wetlands. [Preview Abstract] |
Tuesday, November 23, 2010 3:31PM - 3:44PM |
RS.00003: Shell selection of hermit crabs is influenced by fluid drag Barbara Casillas, Rene Ledesma, Guillermina Alcaraz, Roberto Zenit The flow around gastropod shells used by hermit crabs (Calcinus californiensis) was visualized experimentally. These crabs choose their shells according to many factors; we found that the choice of shell (shape and weight) is directly related to the drag caused over them by the exposure to wave action. Tests were conducted in a wind tunnel to investigate flow differences for shells of various shapes. A particle image velocimetry (PIV) system was used to visualize the flow field. The images above show the flow field around two types of shells (Thais speciosa and Nerita scabircosta) for Reynolds numbers of O(10$^5$). Using a control volume analysis, the drag coefficient was inferred. Several shell geometries, orientations and mean flow velocities were tested. In this talk, the flow and drag force will be shown for the different arrangements. A discussion of the relation between drag and shape will be presented. [Preview Abstract] |
Tuesday, November 23, 2010 3:44PM - 3:57PM |
RS.00004: Numerical simulation on the assimilation of substrate by microorganisms in a turbulent flow Marion Linkes, Pascal Fede, Jerome Morchain, Philippe Schmitz A strong decrease in the conversion yield of substrate into biomass is constantly observed in fed-batch bioreactors when passing from a laboratory to an industrial scale because of concentration gradients that influence the biomass behaviour. In this work, the focus was emphasised on the effect of the mixing on the microorganisms. This was addressed through a one-dimensional diffusion model for the transport of substrate towards the cell with specific boundary conditions at the microorganism, that plans to simulate its limiting behaviour. Diversified far field concentrations in substrate were investigated and aimed to mimic the several states of mixing at the small scale of the flow. The influence of relevant parameters of the entering substrate concentration was scrutinized in term of interfacial response at the cell interface. This interfacial response takes into account the concentration and assimilitation rate at the microorganism interface, and its analysis shows results in good agreement with different experimental observations and the cell affinity for the substrate has been determined taking the mixing state of the latter. [Preview Abstract] |
Tuesday, November 23, 2010 3:57PM - 4:10PM |
RS.00005: Power generation by flagella-propelled Serratia Marcescens Trung-Hieu Tran, Min Jun Kim, Doyoung Byun In this study, we present electrical power generation by using swimming Serratia marcescens which is a rod shaped bacterium species and has about 10 um long and about 20 nm thin helical filaments. Flow in micro channel is driven by bacteria attached on the wall, which is around 25 to 50 $\mu$m/sec. The driven electrolyte solution flow (buffer solution containing high concentration of S. marcescens) may be considered as movement of conductor. If we place permanent magnets on the top and bottom of the micro channel and electrodes on side walls in the micro channel, electrical current could be generated by the principle of Lorentz force acting on the moving charges. The potential between the two electrodes was measured to be up to 10mV and the electrical current was about 10pA with external load 50 Ohm. Even if the energy generated by bacteria swimming is small, it demonstrated the possible generation of power, which requires in-depth further research. [Preview Abstract] |
Tuesday, November 23, 2010 4:10PM - 4:23PM |
RS.00006: ABSTRACT WITHDRAWN |
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