• Title, Summary, Keyword: 에크만경계층

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Flow Analysis in a Rotating Container with Axial Injection and Radial Ejection (축방향 유입과 반경방향 유출이 있는 회전용기 내의 유동해석)

  • Park, Jun-Sang;Sohn, Jin-Gug
    • Journal of the Korean Society of Visualization
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    • v.9 no.1
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    • pp.49-54
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    • 2011
  • An investigation has been made of a viscous incompressible flow in a circular cylindrical tank. The flow is driven by the spinning bottom disk of tank together with/without central injection and radial uniform-ejection through the sidewall. Numerical solutions of steady and unsteady flows to 3-dimensional Navier-Stokes equation were obtained for several cases of injection strength. In a moderate flow rate of injection, the mass transfer occurs through the boundary layers but, as the flow rate increases, the inner region far from the container walls takes part in mass transfer.

Effects of Angular Velocity Change on the Flow Field and Heat Transfer in the Bridgman Crystal Growth Process (Bridgman 결정성장공정에서 각속도변화가 유동장 및 열전달에 미치는 영향)

  • 문승재;노승탁
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.3
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    • pp.771-783
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    • 1995
  • A simplified model for the so-called ACRT(accelerated crucible rotation technique) Bridgman crystal growth was considered in order to investigate the principal effects of the periodic variation of angular velocity. Numerical solutions were obtained for Ro=0.5, Ra=4.236*10$_{6}$ and E=2.176*10$^{-3}$ . The effects of spin-up process combined with natural convection was investigated as a preliminary study. The spin-up time scale for the present problem was a little larger than that observed for homogeneous spin-up problems. Numerical results reveal that over a time scale of (H$^{2}$/.nu..omega.$_{f}$)$^{1}$2/ the forced convection due to the formation of Ekman layer predominates. When the state of rigid body rotation is attained, natural convection due to buoyancy emerges as the main driving force and them the steady-state is approached asymptotically. Based on our preliminary results with simple spin-up, several fundamental features associated with variation of rotation speed are successfully identified. When a periodic variation of angular velocity was imposed, the system response was also periodic. Due to effect of mixing, the heat transfer was enlarged. From the analysis of time-averaged Nusselt number along the bottom surface the effect of a periodic variation of angular velocity on the interface location could be indirectly identified.d.