• Title/Summary/Keyword: 임계 Rayleigh수

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Dual Solutions for Steady Natural Convection of Air in Horizontal Cylindrical Annulus (수평 원주형 환형내에서의 정상상태의 공기의 자연대류에 대한 이중해)

  • Yu, Ju-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.9
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    • pp.2981-2990
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    • 1996
  • Dual solutions for steady natural convection of air between two horizontal concentric cylinders are numerically investigated in the range of $D_i$/TEX>/L(=diameter of inner cylinder/gap width)$\leq$10. It is found that, when the Rayleigh number based on the gap width exceeds a certain critical value, a new flow pattern forming two counter-rotating eddies in the half of the annulus can be realized, which is different from the crescent-shaped flow commonly observed. In the new flow pattern, the fluid near the top of the hot inner cylinder moves downward. This solution is found for D$_{i}$/L.geq.0.3, but not for$D_i$/TEX>/L$\leq$0.2. As $D_i$/TEX>/L increase, the critical Rayleigh number is decreased, and tends to a finite limit.t.

Oscillatory Motion of Natural Convective Flow in Partially Divided Square Enclosure (수평격판을 갖는 4각형 밀폐공간내에서 자연대류의 진동유동)

  • 김점수;정인기;송동주
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.10
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    • pp.1963-1970
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    • 1992
  • An oscillatory motion of the natural convection in a two dimensional, partially divided square enclosure heated from below, and fitted with a partition is investigated numerically. The enclosure was composed of the lower hot and the upper cold horizontal walls and the adiabatic vertical walls, and a partition was situated perpendicularly at the mid-height of the one vertical insulated wall. The governing equations are solved by using the finite element method with Galerkin method. The computations were performed with the variation of the length and the thermal conductivity of the partition, and Rayleigh number based on the temperature difference between horizontal walls and the enclosure height with water(Pr=4.95). also, the effect of the inclination angles was studied for the transition to the oscillating flow. As the results, it was found that the intensity and frequency of oscillatory motion were affected significantly by the Rayleigh number and the length of partition. The effect of oscillatory motion was weaken with the increase of the thermal conductivity of partition. The inclination angle for the transition was raised with the increase of Rayleigh number and the length of partition.