• 한국수자원학회논문집
• /
• 제37권5호
• /
• pp.375-386
• /
• 2004

갈수량은 수자원의 개발 및 관리에 매우 중요한 인자중의 하나이다. 신뢰성 높은 갈수량을 측정하기 위해 한국수자원공사는 2000년도에 용담댐 시험유역에 5피트 규격의 파샬플륨을 설치하였다. 파샬플륨은 유량측정을 하기 위해 독특한 모양을 가지고 있으며, 부정확한 유량관측을 유발하는 퇴사문제를 거의 해결한 시설물이다. 본 연구에서는 3차원 CFD (Computational Fluid Dynamics) 모형으로 5가지 수위에 대해서 완전월류(free flow)시 파샬플륨의 유동을 해석하였다. CFD모형에 의해 산정된 결과와 ISO에 제시된 유량공식, USBR에 제시된 유량공식 및 수위-유량관계식으로 산정한 유량을 비교하였다. 그 결과 ISO와 USBR의 공식에 의해 산정된 유량은 거의 동일했으나, 3차원 CFD모형에 의한 유량은 경험공식에 의한 유량보다 9%정도 크게 나타났고 수위-유량관계식에 의한 유량은 경험공식에 의한 유량보다 16%정도 작게 나타났다.

• 멤브레인
• /
• 제27권4호
• /
• pp.358-366
• /
• 2017

연료전지용 전해질막의 성능에 있어서 가장 중요한 요소는 수소이온이 전해질막 내부에 형성된 수화채널을 따라서 얼마나 빨리 전달될 수 있느냐이다. 여기에는 수화채널의 모폴로지 및 수소이온의 확산도 등이 매우 중요한 요소가 되는데, 이를 규명하기 위하여 다양한 분자동역학 전산모사 연구가 진행되고 있다. 분자동역학 계산에 있어서 각 원자의 움직임 및 상호작용을 미리 변수화 시켜 놓은 force-field는 필수 요소 중 하나로서, 본 연구에서는 이러한 force-field의 종류가 전해질막 전산모사에 미치는 영향을 분석하기 위하여, 다양한 force-field를 이용하여 연료전지용 전해질막의 수소이온 확산도를 계산하였다. 이 과정에서 non-bonding interaction을 결정하는 전하 값이 수화채널 모폴로지 형성에 매우 중요한 역할을 한다는 것이 밝혀졌으며, COMPASS force-field가 가장 정확한 수소이온 확산도 값을 얻음으로써 연료전지용 전해질막의 전산모사에 있어서 가장 적절한 force-field일 것으로 판단된다. 이러한 force-field의 적절한 선정은 최종 분자 구조 뿐만 아니라 수소이온 확산도에도 큰 영향을 주는 것을 알 수 있었으며, 연료전지용 전해질막 전산모사 수행 시에는 이러한 부분을 충분히 감안하여 force-field를 선택하여야 할 것이다.

• Bulletin of the Korean Chemical Society
• /
• 제34권9호
• /
• pp.2711-2719
• /
• 2013

Hydrogen bonding interaction between alcohols and water molecules is an important characteristic in the aqueous solutions of alcohols. In this paper, a series of molecular dynamics simulations have been performed to investigate the aqueous solutions of low molecular weight alcohols (methanol, ethylene glycol and glycerol) at the concentrations covering a broad range from 1 to 90 mol %. The work focuses on studying the effect of the alcohols molecules on the hydrogen bonding of water molecules in binary mixtures. By analyzing the hydrogen bonding ability of the hydroxyl (-OH) groups for the three alcohols, it is found that the hydroxyl group of methanol prefers to form more hydrogen bonds than that of ethylene glycol and glycerol due to the intra-and intermolecular effects. It is also shown that concentration has significant effect on the ability of alcohol molecule to hydrogen bond water molecules. Understanding the hydrogen bonding characteristics of the aqueous solutions is helpful to reveal the cryoprotective mechanisms of methanol, ethylene glycol and glycerol in aqueous solutions.

• 한국소음진동공학회논문집
• /
• 제24권6호
• /
• pp.462-469
• /
• 2014

After drilling operations at the offshore plant, crude oil is producted under high pressure. After that time, oil recovery is reduced, because the pressure of the pipe inside is low during the secondary produce. At that time injection sea water at the pipe inside through water injection pump that the device increase to recovery. A variety of mathematical analysis during the detailed design analysis was not made through the dynamics characteristic at the domestic company. 2D model has reliability of analysis results for the uncomplicated model. Also element and the node the number of significantly less than in the 3D model. So, the temporal part is very effective. In addition, depending on the quality of mesh 3D is a real model and FEM model occurs error. So, user needs a lot of skill. In this paper, a 2D finite element analysis was performed through the dynamics analysis and the study model was validated.

• 한국수산과학회지
• /
• 제37권1호
• /
• pp.24-32
• /
• 2004

A mathematical model is used to investigate nitrogen dynamics in the intensive aquaculture ponds in the western coast of Korea. Parameters associated with water quality, sediments and growing of shrimp (Fenneropenaeus chinensis) are measured to calibrate the model for feeding ponds A and B and storage ponds. The model describes the fate of nitrogen including loadings of ammonia from feeds, phytoplankton assimilation, nitrification, sedimentation, volatilization and discharge. The model obtains good agreements with the measured values of TAN $(NH_4,\;NH_3),\;NO(NO_2,\;NO_3)$ and Chl (chlorophyll a). Impacts of water exchange on TAN and Chl are investigated, showing that the range of 0.01-0.2 (/day) cannot effectively reduce TAN but reduces Chl. Nitrogen in the ponds A is removed by sedimentation $66\%,$ volatilization $8\%,$ discharge of particulate and dissolved $8\%.$ The pond B shows $56\%\;and\;26\%$ of sedimentation and volatilization, respectively, to yield $10\%.$ decrease and 8c/o increase compared to those in the pond A. While the pond A has larger area (1.02:0.66 ha) and same stocking density (0.025 md./L) at the beginning of culture, the pond B obtains higher stocking density (0.0065:0.0091 md./L), longer feeding period (103:121 day) and resultant higher shrimp production (1.15:2.13 t/ha/cycle) at harvest. This is possibly due to the hydraulic characteristics driven by paddlewheels. At low ratio of the low speed area and the pond area, the rate of sedimentation is high, while the rate of gas exchange is low. Thus, the measurement and model analysis suggest that water quality and shrimp production are positively correlated with the hydraulic characteristics in the shrimp ponds.

• Environmental Engineering Research
• /
• 제25권4호
• /
• pp.498-505
• /
• 2020

This study analyzes the velocity and pressure incurred by protruding shapes installed within the inlet part of a pressurized membrane module during operation to determine the fluid flow distribution. In this paper, to find the flow distribution within a module, it investigates the velocity and pressure values at cross-sectional and outlet planes, and 9 sections classified on outlet plane using computational fluid dynamics. From the Reynolds number (Re), the fluid flow was estimated to be turbulent when the Re exceeded 4,000. In the vertical cross-sectional plane, shape 4 and 6 (round-type protrusion) showed the relatively high velocity of 0.535 m/s and 0.558 m/s, respectively, indicating a uniform flow distribution. From the velocity and pressure at the outlet, shape 4 also displayed a relatively uniform fluid velocity and pressure, indicating that fluid from the inlet rapidly and uniformly reached the outlet, however, from detailed data of velocity, pressure and flowrate obtained from 9 sections at the outlet, shape 6 revealed the low standard deviations for each section. Therefore, shape 6 was deemed to induce the ideal flow, since it maintained a uniform pressure, velocity and flowrate distribution.

• 한국전산유체공학회지
• /
• 제20권2호
• /
• pp.1-6
• /
• 2015

In this study, a numerical prediction on propulsive performance of a ducted propeller in open water condition was carried out by solving Reynolds averaged Navier-Stokes(RANS) equation using computational fluid dynamics(CFD). A configuration of propeller Ka-470 inside duct 19A was considered. Hexahedral grid system was generated by dividing whole computational domain into three separate regions; propeller, duct and outer flow region. A commercial CFD software, ANSYS-CFX was used for numerical simulations. Results were compared with experimental data and showed considerable improvement in accuracy, in comparison to those from surface panel method which is based on potential flow assumption. The results also exhibited the importance of grid system within the gap between the inner surface of duct and blade tip for accurate prediction of propulsive performance of ducted propeller.

• 한국해양공학회지
• /
• 제28권4호
• /
• pp.345-350
• /
• 2014

A special usage impeller pump for ballast water treatment is part of an offshore plant's structure. It has to maintain a high corrosion resistance in an extreme environment, in which it can contact several kinds of aqueous solutions. The duplex stainless steel used in such severe environments is known to have corrosion resistance and excellent mechanical properties. This study estimated the performance of an impeller pump system designed using duplex stainless steel through a computational fluid dynamics analysis. As a result, it was determined that the pressure drop increases and the impeller performance is lowered if the equivalent roughness is enlarged. The surface precision of the duplex stainless steel must be consistently maintained. If thisis the case, it was determined that the existing STS steel can be substituted for the Duplex stainless steel.

• 상하수도학회지
• /
• 제28권2호
• /
• pp.225-233
• /
• 2014

This paper presents a Computational Fluid Dynamics(CFD) based simulation and experimental tracer test of flow pattern and turbulent energy dissipation inside a serpentine flocculation basin with continuous operation. Research focused on the evaluation of a specific flow pattern on the hydraulic behavior on the flocculation basin. From the results of CFD simulation and actual tracer test, both results were in good accordance with each other. Also, each Morill index were calculated as 1.5 from CFD simulation and 1.7 from actual tracer test, respectively. Especially, turbulence energy was dissipated relatively higher in the vicinity of inlet to the flocculation basin than other region. The differences between the CFD simulation and actual tracer test were 1.4 min in $T_{50}$, and 1.3 min in $T_p$, respectively.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제2권3호
• /
• pp.139-145
• /
• 2010

In the present study, we conducted resistance test, propeller open water test and self-propulsion test for a ship's resistance and propulsion performance, using computational fluid dynamics techniques, where a Reynolds-averaged Navier-Stokes equations solver was employed. For convenience of mesh generation, unstructured meshes were used in the bow and stern region of a ship, where the hull shape is formed of delicate curved surfaces. On the other hand, structured meshes were generated for the middle part of the hull and the rest of the domain, i.e., the region of relatively simple geometry. To facilitate the rotating propeller for propeller open water test and self-propulsion test, a sliding mesh technique was adopted. Free-surface effects were included by employing the volume of fluid method for multi-phase flows. The computational results were validated by comparing with the existing experimental data.