• The Korean Journal of Rheology
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• v.8 no.2
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• pp.92-102
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• 1996

두 종류의 열방성 액정고분자와 세종류의 엔지니어링 고분자와의 블렌드들에 대해 유변학적/형구학적 연구를 한 결과 블렌드의 유동거동과 물성이현저히 다른 두 그룹으로 나 뉘어짐을 발견하였다. 즉 연속상의 조업온도가 분산상의 전이온도보다 높은 그룹A에 속하 는 블렌드의 전단점도/신장점도는 액정고분자를 첨가할수록 첨가할수록 감소하고 블렌드의 신장점도는 연속상의 그것처럼 신장변형률속도가 커질수록 증가하였다. 또한 분산상의 점도 가 연속상의 그것보다 작아서 분산상이 미세섬유구조의 형태로 존재하였다. 이와 대조적으 로 연속상의 조업온도가 액정고분자의 전이온도보다 낮은 그룹 B에 속하는 블렌드는 반대 의 거동을 보였고 분산상의 미세섬유구조가 존재하지 않았다. 그러나 연신변형이 주가 되는 방사공정을 거치면 그룹A와 B블렌드 공히 분산상이 비슷한 미세섬유구조의 형태로 존재하 고 기계적 성질도 크게 향상되는 결과를 보였다. 이는 블렌드내의 신장유동이 분산상의 섬 유구조형상에 결정적 역할을 하기 때문이라 판단된다.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.505-514
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• 1998

Flow pattern of air-water two phase flow depends on the conditions of pressure void fraction and channel geometry. We classify the flow pattern by measuring the output signal of the conductivity probe. under the classified flow pattern we mount a visualization equipment on the test section and take pictures. We vary the concentration of pure solvent and polymer to measure local void fraction. We know that the maximum point position of local void fraction distribution move from the center of the pipe to the wall of the pipe as JSL increase when JSA is constant in two phase flow. But we find that the maximum point position of local void friction move from the wal of the pipe to the center of the pipe when polymer concentration increase.

• Journal of Energy Engineering
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• v.18 no.2
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• pp.87-92
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• 2009

An experimental investigation is conducted to study a 2-phase vertically upward hydraulic transport of solid particles by water and non-Newtonian fluids in a slim hole concentric annulus with rotation of the inner cylinder. Rheology of particulate suspensions in viscoelastic fluids is of importance in many applications such as particle removal from surfaces, transport of proppants in fractured reservoir and cleaning of drilling holes, etc. In this study, a clear acrylic pipe was used in order to observe the movement of solid particles. Annular velocities varied from 0.3 m/s to 2.0 m/s. The mud systems included fresh water and CMC solutions. Main parameters considered in the study were inner-pipe rotation speed, fluid flow regime and particle injection rate. A particle rising velocity and pressure drop in annulus have been measured for fully developed flows of water and of aqueous solutions. For both water and 0.2% CMC solutions, the higher the concentration of the solid particles is, the larger the pressure gradients become.

• Journal of the Korean Institute of Gas
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• v.2 no.4
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• pp.53-59
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• 1998

Flow pattern of air-water two phase flow depends on the conditions of pressure drop, void fraction, and channel geometry. Drag reduction in the two phase flow can be applied to the transport of crude oil, phase change systems such as chemical reactor, pool and boiling flow, and to present cavitation which occurs in pump impellers. But the research on drag reduction in two phase flow is not intensively investigated. Therefore, experimental investigations have been carried out to analyze the drag reduction produced and void fraction by Co-polymer(A611p) addition in the two phase flow system. We find that the maximum point position of local void friction moves from the wall of the pipe to the center of the pipe when polymer concentration increases. Also we find that the polymer solution changes the characteristics of the two phase flow. And then we predict that it is closely related with the drag reduction.

• Proceeding of EDISON Challenge
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• 2016.11a
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• pp.55-57
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• 2016

본 연구에서는 초고속 자기부상열차의 단면도를 통하여 2-D형상을 모델링하고 이를 기반으로 항력과 유동 특성에 대한 분석을 수행하였다. 유동의 마하수가 0.3 이상임을 고려하여 압축성 모델이 사용되었고, 난류모델은 Menter's k-w SST(Shear Stress Transport)모델을 적용시켰다. 2-D 해석과 자기부상열차의 특성상 열차가 공기중에서 주행하고 있는 것으로 가정하고 공력 특성을 해석하였다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.1
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• pp.107-119
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• 1995

Turbulent flow characteristics and heat transfer in a three-dimensional room with a desk-type heat generating obstacle have been investigated numerically by the k-$\varepsilon$ two equation turbulence model. The room mole has one supply opening on the ceiling and two exhaust openings on the side walls. Th results of the flow structure and heat transfer have been represented for air for the inlet velocities in the range 0.1-10.0m/s. As the results of the three dimensional simulations, the relationships between mean Nusselt number and Reynolds number are clarified.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.2
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• pp.1-12
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• 1996

Hydrodynamic characteristics of shipping water on deck are investigated by using a simplified two-dimensional model. Formulation of the shipping water on deck leads to a nonlinear hyperbolic system of equations based on the shallow-water wave theory. Time-domain solution of these equations are obtained numerically using a finite difference method which adopts predictor-corrector method for time-marching and 2nd upwind differencing method for convection term calculation. To confirm the validity of the present numerical method, we calculated some shallow-water wave problems accompanying a bore and compared the obtained results with the analytic solutions. We found good agreements between them. Though the calculation results of shipping water on deck, we show that the shipping water flows into the deck as a rarefying wave arid grows into a bore after colliding with a deck structure. Also we examined the effects of acceleration and slope of deck and found that they have significant influences on the flow of shipping water.

• Environmental engineer
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• s.137
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• pp.30-36
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• 1998

• Journal of Korean Society of Environmental Engineers
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• v.27 no.5
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• pp.542-548
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• 2005

A fluidized bed reactor containing porous media has been known to be effective for nitrogen and organic matters removal in wastewater. The porous media which attached microbes plays important roles in simultaneous nitrification/denitrification (SND) due to coexistence of oxic, anaerobic and anoxic zone. For SND reaction, oxygen and organic substrates should be effectively diffused from wastewater into the intra-carrier zone. However, the overgrowth heterotrophic microbes at the surface of porous media may restrict from substrates diffusion. From these viewpoints, the existence and effect of heterotrophic bacteria at surface of porous media might be the key point for nitrogen removal. A porous media-membrane hybrid process was found to have improved nitrogen removal efficiency, due to stimulated denitrification as well as nitrification. Microelectrode studies revealed that although intra-media denitrification rate in a conventional fluidized bed was limited by organic carbon, this limitation was reduced in the hybrid process, resulting in the increased denitrification rate from 0.5 to $4.2\; mgNO_3-N/L/hr$.

• Journal of Energy Engineering
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• v.17 no.4
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• pp.218-226
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• 2008

A component-scale two-phase analysis code has been developed for a realistic simulation of two-phase flow transients in a light water nuclear reactor component. In the code, a two-fluid three-field model is adopted and the governing equations are solved on an unstructured mesh. For the numerical solution scheme, the semi-implicit method used in the RELAP5 code was selected, which has been proved to be very stable and accurate for most of practical applications. However, some modifications were needed for its application to an unstructured non-staggered grid. This paper presents the modified semi-implicit numerical method for unstructured grid and the preliminary results of the calculations.