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Moving Fluid (moving + fluid)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Numerical investigation of heat transport and fluid flow during the seeding process of oxide Czochralski crystal growth Part 1: non-rotating seed

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2007
M. H. Tavakoli
Abstract For the seeding process of oxide Czochralski crystal growth, the flow and temperature field of the system as well as the seed-melt interface shape have been studied numerically using the finite element method. The configuration usually used initially in a real Czochralski crystal growth process consists of a crucible, active afterheater, induction coil with two parts, insulation, melt, gas and non-rotating seed crystal. At first the volumetric distribution of heat inside the metal crucible and afterheater inducted by the RF coil was calculated. Using this heat source the fluid flow and temperature field were determined in the whole system. We have considered two cases with respect to the seed position: (1) before and (2) after seed touch with the melt. It was observed that in the case of no seed rotation (,seed = 0), the flow pattern in the bulk melt consists of a single circulation of a slow moving fluid. In the gas domain, there are different types of flow motion related to different positions of the seed crystal. In the case of touched seed, the seed-melt interface has a deep conic shape towards the melt. It was shown that an active afterheater and its location with respect to the crucible, influences markedly the temperature and flow field of the gas phase in the system and partly in the melt. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Small-scale fluid motion mediates growth and nutrient uptake of Selenastrum capricornutum

FRESHWATER BIOLOGY, Issue 6 2006
T. A. WARNAARS
Summary 1. A fluid-flow reactor using submersible speakers was constructed to generate small-scale fluid motion similar to conditions measured in open water environments; flow was quantified by particle image velocimetry. Additionally a Couette-type rotating cylinder was used to generate shear flows; flow was quantified using an optical hotwire probe and torque measurements. Growth rates of the green alga Selenastrum capricornutum were determined from changes in cell counts and viability was tested using the fluorogenic probe fluoresceine diacetate. 2. Evidence that fluid motion directly affects growth rates was obtained as a significant difference between growth in a moving versus non-moving fluid. A near 2-fold increase in growth rate was achieved for an energy dissipation rate of , = 10,7 m2 s,3; a rate common in lakes and oceans. The onset of the viability equilibrium, identified as the day of the test period when the number of active cells equalled non-active cells, was delayed by 2 days for moving fluid conditions as compared with a non-moving fluid. 3. Nutrient uptake was determined by a decrease in the bulk fluid concentration and cellular phosphorus concentration was also estimated. The thickness of the diffusive sublayer surrounding a cell, a zone dominated by molecular diffusion, was estimated. Increasing fluid motion was found to decrease the thickness of this layer. The Sherwood number (ratio of total mass flux to molecular mass flux) showed that advective flux surrounding cells dominated molecular diffusion flux with regard to Péclet numbers (ratio of advective transport to molecular diffusion transport). Fluid motion facilitated uptake rates and resulted in increased growth rates, compared with no-flow conditions. The rate-of-rotation and the rate-of-strain in a moving fluid equally mediated the diffusive sublayer thickness surrounding the cells. Our study demonstrates that small-scale fluid motion mediates algal growth kinetics and therefore should be included in predictive models for algal blooms. [source]

Kinetic responses of Dunaliella in moving fluids

BIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010
Ahammed Anwar Chengala
Abstract The objective of this work was to quantify the kinetic behavior of Dunaliella primolecta (D. primolecta) subjected to controlled fluid flow under laboratory conditions. In situ velocities of D. primolecta were quantified by micron-resolution particle image velocimetry and particle tracking velocimetry. Experiments were performed under a range of velocity gradients and corresponding energy dissipation levels at microscopic scales similar to the energy dissipation levels of natural aquatic ecosystems. An average swimming velocity of D. primolecta in a stagnant fluid was 41,µm/s without a preferential flow direction. In a moving fluid, the sample population velocities of D. primolecta follow a log-normal distribution. The variability of sample population velocities was maximal at the highest fluid flow velocity in the channel. Local fluid velocity gradients inhibited the accrual of D. primolecta by twofold 5 days after the initiation of the experiment in comparison to the non-moving fluid control experiment. Biotechnol. Bioeng. 2010;107: 65,75. © 2010 Wiley Periodicals, Inc. [source]

Multiphase CFD Simulation of a Solid Bowl Centrifuge

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2009
X. Romaní Fernández
Abstract This study presents some results from the numerical simulation of the flow in an industrial solid bowl centrifuge used for particle separation in industrial fluid processing. The computational fluid dynamics (CFD) software Fluent was used to simulate this multiphase flow. Simplified two-dimensional and three-dimensional geometries were built and meshed from the real centrifuge geometry. The CFD results show a boundary layer of axially fast moving fluid at the gas-liquid interface. Below this layer there is a thin recirculation. The obtained tangential velocity values are lower than the ones for the rigid-body motion. Also, the trajectories of the solid particles are evaluated. [source]