• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.4
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• pp.251-256
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• 2002

The average diffusion time of a polyacrylamide solution was determined by measuring the terminal velocities of the falling balls. The diffusion time increased as the polyacrylamide concentration increased. The PIV (Particle Image Velocimetry) system was employed to visualize the flow phenomena around balls. For a time interval of 30 seconds in the 2000 wppm, velocity vectors were larger than in case of 0 seconds, 40 seconds and 50 seconds in the falling ball. However, in the Newtonian fluid, flow vsualization around balls were performed at both upstream and downstream of the falling ball.

• Transactions of the Korean Society of Mechanical Engineers
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• v.5 no.3
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• pp.238-243
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• 1981

An empirical formula for the mass flow rate in natural convection flume above a spherical heated body which is submerged in a finite fluid contained in a tank was determined. The ratio of depth of submergence to diameter of the sphere for which the sphere sensed as infinite medium was found to be bigger than 7. A dimensionless heat transfer correlation for the natural convection from a sphere was determined for Gr.Prq etween 7x10$\^$7/ and 2x10$\^$8/ also.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.106-109
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• 2006

A large eddy simulation with explicit filters on unstructured mesh is presented. Two explicit filters are adopted for reducing the aliasing error of the nonlinear convective term and measuring the level of subgrid scale velocity fluctuation, respectively. The developed subgrid scale model is basically eddy viscosity model which depends on the explicitly filtered fields and needs no additional ad hoc wall treatment such as van Driest damping function. As a validation problem, the flows around a sphere at several Reynolds numbers, including laminar and turbulent regimes, are calculated and compared to experimental data and numerical results in the literature.