• 설비공학논문집
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• 제6권3호
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• pp.302-314
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• 1994

The effects of the inclination of enclosure and partition on natural convective flow and heat transfer were 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 positioned perpendicularly at the mid-height of one vertical insulated wall. The governing equations are solved by using the finite element method with Galerkin method. The computations were performed with the variations of the partition length and Rayleigh number based on the temperature difference between two horizontal walls and the enclosure height with water(Pr=4.95). The effects of the inclination angle of enclosure and partition on the heat transfer within an enclosure were also studied. As the results, the increase of the inclination angle of enclosure rapidly raised the heat transfer rate, while the inclination angle for the maximum Nusselt number was retarded with the increase of the partition length and the decrease of the heat transfer rate became larger in proportion to the increase of the partition length. The Nusselt number obtained by the inclination of partition was smaller than that of the inclination of enclosure. However, the difference of the heat transfer rates was considerably decreased at the longer partition lengths and the trends for the variation of the average Nusselt number were more similar with that of the inclination of enclosure. The upward oriented partition increases the convective heat transfer distinctly in contrast to that of the inclination of enclosure as the partition length increases.

• 대한기계학회논문집B
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• 제40권3호
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• pp.181-189
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• 2016

수평 관군에 대하여 수직이고 상향으로 흐르는 2상 유동에 의한 감쇠비를 예측하기 위한 해석모델이 Sim에 의하여 개발되었다. 이 모델에서 평가된 2상 유동의 기공률, 압력손실 등의 유동변수는 기존의 실험식을 사용하여 계산하였다. 그러나 관군의 경우에 사용하기에는 약간의 개선이 요구된다. 따라서 관군 내에 흐르는 2상 유동의 유동 변수에 대한 더 많은 정보를 획득하기 위하여 실험적으로 연구할 필요가 있다. 실험은 공기 - 물의 2상 유동이 흐르는 정사각형 배열 관군에서의 압력계수와 2상 유동 마찰승수를 계산하기 위하여 수행되었다. 피치 직경 비는 1.35이었고, 실린더의 직경은 18 mm이다. 압력센서와 신호처리 장치를 이용하여 관군에서의 압력차를 측정하였다. 2상 유동 마찰승수와 오일러수를 계산하기 위하여 관군에 적용되는 비균질 유동의 기공률은 Feenstra 등의 실험식을 사용하여 계산하였다. 균질과 비균질 2상 유동의 마찰승수와 오일러의 수를 실험적으로 구하고 Sim의 어림적 모델에 근거한 이론적 해석 결과와 비교 분석하였다.

• 한국기후변화학회지
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• 제34권22호
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• pp.9093-9113
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• 2021

This study examines the role of the relative wind (RW) effect (wind relative to ocean current) in the regional ocean circulation and extratropical storm track in the south Indian Ocean. Comparison of two high-resolution regional coupled model simulations with and without the RW effect reveals that the most conspicuous ocean circulation response is the significant weakening of the overly energetic anticyclonic standing eddy off Port Elizabeth, South Africa, a biased feature ascribed to upstream retroflection of the Agulhas Current (AC). This opens a pathway through which the AC transports the warm and salty water mass from the subtropics, yielding marked increases in sea surface temperature (SST), upward turbulent heat flux (THF), and meridional SST gradient in the Agulhas retroflection region. These thermodynamic and dynamic changes are accompanied by the robust strengthening of the local low-tropospheric baroclinicity and the baroclinic wave activity in the atmosphere. Examination of the composite life cycle of synoptic-scale storms subjected to the high-THF events indicates a robust strengthening of the extratropical storms far downstream. Energetics calculations for the atmosphere suggest that the baroclinic energy conversion from the basic flow is the chief source of increased eddy available potential energy, which is subsequently converted to eddy kinetic energy, providing for the growth of transient baroclinic waves. Overall, the results suggest that the mechanical and thermal air-sea interactions are inherently and inextricably linked together to substantially influence the extratropical storm tracks in the south Indian Ocean.

• 대기
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• 제22권1호
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• pp.29-45
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• 2012

An unusual autumn storm developed rapidly in the western part of the East sea on the early morning of 23 October 2006. This storm produced a record-breaking heavy rain and strong wind in the northern and middle part of the Yeong-dong region; 24-h rainfall of 304 mm over Gangneung and wind speed exceeding 63.7 m $s^{-1}$ over Sokcho. In this study, MTSAT-1R (Multi-fuctional Transport Satellite) water vapor and infrared channel imagery are examined to find out some features which are dynamically associated with the development of the storm. These features may be the precursor signals of the rapidly developing storm and can be employed for very short range forecast and nowcasting of severe storm. The satellite features are summarized: 1) MTSAT-1R Water Vapor imagery exhibited that distinct dark region develops over the Yellow sea at about 12 hours before the occurrence of maximum rainfall about 1100 KST on 23 October 2006. After then, it changes gradually into dry intrusion. This dark region in the water vapor image is closely related with the positive anomaly in 500 hPa Potential Vorticity field. 2) In the Infrared imagery, low stratus (brightness temperature: $0{\sim}5^{\circ}C$) develops from near Bo-Hai bay and Shanfung peninsula and then dissipates partially on the western coast of Korean peninsula. These features are found at 10~12 hours before the maximum rainfall occurrence, which are associated with the cold and warm advection in the lower troposphere. 3) The IR imagery reveals that two convective cloud cells (brightness temperature below $-50^{\circ}C$) merge each other and after merging it grows up rapidly over the western part of East sea at about 5 hours before the maximum rainfall occurrence. These features remind that there must be the upward flow in the upper troposphere and the low-layer convergence over the same region of East sea. The time of maximum growth of the convective cloud agrees well with the time of the maximum rainfall.