• Title, Summary, Keyword: Flow

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A Study on the Estimation of River Management Flow in Urban Basin (도시유역의 하천유지용수 산정에 관한 연구)

  • 이영화
    • Journal of Environmental Science International
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    • v.5 no.3
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    • pp.377-385
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    • 1996
  • This study aims at the estimation of a river management flow in urban basin analyzing Sinchun basin to be the tributary of Kumho river basin. The river management flow has to satisfy a low flow as natural flow and an environmental preservation flow estimated by a dilution flow to satisfy a target water quality in drought flow. Therefore for the estimation of a river management flow in Sinchun in this study, first Tank model as a basin runoff model estimates a low flow, a drought flow from a flow duration curve in Sinchun, second QUAL2E model as water quality model simulates water quality in Sinchun and estimates environmental preservation flow to satisfy a target water qua%its, BOD 8 mg/l by a dilution flow derived from Kumho river, Nakdong river and around water. And the river management flow is estimated by addition of a use flow and a loss flow to more flow between a low-flow and an environmental preservation flow.

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LDV Measurement, Flow Visualization and Numerical Analysis of Flow Distribution in a Close-Coupled Catalytic Converter

  • Kim, Duk-Sang;Cho, Yong-Seok
    • Journal of Mechanical Science and Technology
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    • v.18 no.11
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    • pp.2032-2041
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    • 2004
  • Results from an experimental study of flow distribution in a close-coupled catalytic converter(CCC) are presented. The experiments were carried out with a flow measurement system specially designed for this study under steady and transient flow conditions. A pitot tube was a tool for measuring flow distribution at the exit of the first monolith. The flow distribution of the CCC was also measured by LDV system and flow visualization. Results from numerical analysis are also presented. Experimental results showed that the flow uniformity index decreases as flow Reynolds number increases. In steady flow conditions, the flow through each exhaust pipe made some flow concentrations on a specific region of the CCC inlet. The transient test results showed that the flow through each exhaust pipe in the engine firing order, interacted with each other to ensure that the flow distribution was uniform. The results of numerical analysis were qualitatively accepted with experimental results. They supported and helped explain the flow in the entry region of CCC.

Hydraulic Behavior and Characteristic Analysis by Steady & Unsteady Flow Analysis of Natural Stream (하도 합류부의 정류.부정류해석에 따른 수리학적 변화 특성 분석)

  • Ahn, Seung-Seop;Yim, Dong-Hee;Park, Ro-Sam;Kwak, Tae-Hwa
    • Journal of Environmental Science International
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    • v.17 no.9
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    • pp.957-968
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    • 2008
  • The purpose of this study is to analyze the characteristics of hydraulic behavior of the natural channel flow according to the temporal classification mode, and thus propose the hydraulic analysis method for future channel design. For analysis, the temporal flow characteristics of the channel section was divided into the steady flow and the unsteady flow. For hydraulic analysis, the HEC-RAS model, which is a one-dimensional numerical analysis model, and the SMS-RAM2 model, which is a two-dimensional model, were used and the factors used for analysis of hydraulic characteristics were flood elevation and flow rate. The flow state was analyzed on the basis of the one-dimensional steady flow and unsteady flow for review. In the unsteady flow analysis the flow rate changed by $(-)0.16%{\sim}(+)0.26%$, and the flood elevation varied by $(-)0.35%{\sim}(+)0.51%$ as compared to the values in the steady flow analysis. Given these results, in the one-dimensional flow analysis based on the unsteady flow the flood elevation and flow rate were greater than when the analysis was done on the basis of the steady flow. The flow state was analyzed on the basis of the two-dimensional steady flow and unsteady flow. In the unsteady flow analysis the flow rate varied by $(-)0.16%{\sim}(+)1.08%$, and the flood elevation changed by $(-)0.24%{\sim}(+)0.41%$ as compared to the values in the steady flow analysis. Given these analysis results, in the two dimensional flow analysis based on the unsteady flow, the flood elevation and flow rate were greater than when the analysis was done on the basis of the steady flow.

Predictions of non-uniform tip clearance effects on the flow field in an axial compressor

  • Kang, Young-Seok;Kang, Shin-Hyoung
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.743-750
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    • 2008
  • Asymmetric tip clearance in an axial compressor induces pressure and velocity redistributions along the circumferential direction in an axial compressor. This paper presents the mechanism of the flow redistribution due to the asymmetric tip clearance with a simple numerical modeling. The flow field of a rotor of an axial compressor is predicted when an asymmetric tip clearance occurs along the circumferential direction. The modeling results are supported by CFD results not only to validate the present modeling but also to investigate more detailed flow fields. Asymmetric tip clearance makes local flow area and resultant axial velocity vary along the circumferential direction. This flow redistribution 'seed' results in a different flow patterns according to the flow coefficient. Flow field redistribution patterns are largely dependent on the local tip clearance performance at low flow coefficients. However, the contribution of the main flow region becomes dominant while the tip clearance effect becomes weak as the flow coefficient increases. The flow field redistribution pattern becomes noticeably strong if a blockage effect is involved when the flow coefficient increases. The relative flow angle at the small clearance region decreases which result in a negative incidence angle at the high flow coefficient. It causes a recirculation region at the blade pressure surface which results in the flow blockage. It promotes the strength of the flow field redistribution at the rotor outlet. These flow pattern changes have an effect on the blade loading perturbations. The integration of blade loading perturbation from control volume analysis of the circumferential momentum leads to well-known Alford's force. Alford's force is always negative when the flow blockage effects are excluded. However when the flow blockage effect is incorporated into the modeling, main flow effects on the flow redistribution is also reflected on the Alford's force at the high flow coefficient. Alford's force steeply increases as the flow coefficient increases, because of the tip leakage suppression and strong flow redistribution. The predicted results are well agreed to CFD results by Kang and Kang(2006).

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Flow Entry & Vacancy of Flow table in SDN (SDN에서 Flow table의 Flow Entry 및 Vacancy)

  • Yoo, Seung-Eon;Lym, Hwan-Hee;Kim, Kyung-Tae;Youn, Hee-Young
    • Proceedings of the Korean Society of Computer Information Conference
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    • pp.43-44
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    • 2018
  • SDN(Software Defined Network)는 데이터 부분과 컨트롤 부분을 분리하여 하나의 컨트롤러가 모든 데이터를 담당하는 기술이다. SDN에서 표준 프로토콜 역할을 하는 OpenFlow가 있으며 컨트롤러가 이 OpenFlow 프로토콜을 사용하여 Flow 테이블의 항목을 추가하고 삭제하도록 OpenFlow 스위치를 제어한다. OpneFlow 스위치는 하나 이상의 Flow table을 사용하여 조회하고 채널을 톨해 컨트롤러에 전달한다. 본 논문에서는 Flow Entry 구성도와 Flow가 Flow table에 도달하는 확률, Flow Entry를 분류하는 Vacancy에 대해 설명하였다.

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A Numerical Investigation of Flow and Performance Characteristics of a Small Propeller Fan Using Viscous Flow Calculations

  • Oh, Keon-Je;Kang, Shin-Hyoung
    • Journal of Mechanical Science and Technology
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    • v.16 no.3
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    • pp.386-394
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    • 2002
  • The present work is aimed at investigating an unusual variation in flow and performance characteristics of a small propeller fan at low flow rates. A performance test of the fan showed dual performance characteristics, i.e., radial type characteristics at low flow rates and axial type at high flow rates. Dual performance characteristics of the fan are numerically investigated using viscous flow calculations. The Finite Volume Method is used to solve the continuity and Navier-Stokes equations in the flow domain around a fan. The performance parameters and the circumferentially averaged velocity components obtained from the calculations are compared with the experimental results. Numerical values of the performance parameters show good agreement with the measured values. The calculation simulates the steep variations of performance parameters at low flow rates and shows the difference in the flow structure between high and low flow rates. At a low flow coefficient of $\Phi$=0.2, the flow enters the fan in an axial direction and is discharged radially outward at its tip, which is much like the flow characteristics of a centrifugal fan. The centrifugal effect at low flow rates makes a significant difference in performance characteristics of the fan. As the inlet flow rate increases, flow around the fan changes into the mixed type at $\Phi$=0.24 and the axial discharge at $\Phi$=0.4.

A Study on Flow Rate Characteristics of a Triangular Separate Bar Differential Pressure Flow Meter according to the Variation of Gas Flow Temperature (유동 가스 온도 변화에 따른 삼각 분리 막대형 차압 유량계 유량 특성에 관한 연구)

  • Kim, Kwang-Il;Yoo, Won-Yuel;Lee, Choong-Hoon
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.17 no.4
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    • pp.89-94
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    • 2008
  • Differential pressure flow meters which have a shape of triangular separate bar(TSB) were tested for investigating the flow rate characteristics of the flow meters with varying the temperature of the gas flow. Three kinds of the triangular separate bar flow meters whose aerodynamic angles are different one another are used. The mass flow rate of the flow meters are evaluated using a non-dimensional parameter which includes the gas temperature, exhaust gas pressure and differential pressure at the flow meters, and atmospheric pressure. A burner system which is similar to gas turbine was used for raising the gas flow temperature. The burner system was operated with varying the air/fuel ratio by controlling both the fuel injection rate from the fuel nozzle and air flow rate from a blower. An empirical correlation between the mass flow rate at the TSB flow meter and the non-dimensional parameter was obtained. The empirical correlation showed linear relationship between the mass flow rate and the non-dimensional parameter H. Also, the mass flow rate characteristics at the TSB flow meter was affected by the gas temperature.

COMPUTATIONAL ASSESSEMENT OF OPTIMAL FLOW RATE FOR STABLE FLOW IN A VERTICAL ROTATING DISk CHEMICAL VAPOR DEPOSITION REACTOR (회전식 화학증착 장치 내부의 유동해석을 통한 최적 유량 평가)

  • Kwak, H.S.
    • Journal of computational fluids engineering
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    • v.17 no.1
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    • pp.86-93
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    • 2012
  • A numerical investigation is conducted to search for the optimal flow rate for a rotating-disk chemical vapor decomposition reactor operating at a high temperature and a low pressure. The flow of a gas mixture supplied into the reactor is modeled by a laminar flow of an ideal gas obeying the kinetic theory. The axisymmetric two-dimensional flow in the reactor is simulated by employing a CFD package FLUENT. With operating pressure and temperature fixed, numerical computations are performed by varying rotation rate and flow rate. Examination of the structures of flow and thermal fields leads to a flow regime diagram illustrating that there are a stable plug-like flow regime and a few unfavorable flow regimes induced by mass unbalance or buoyancy. The criterion for sustaining a plug-like flow regime is discussed based on a theoretical scaling argument. Interpretation of the flow regime map suggests that a favorable flow is attainable with a minimum flow rate at the smallest rotation rate guaranteeing the dominance of rotation effects over buoyancy.

sFlow Monitoring for a Virtualization Testbed in KREONET (KREONET에서 가상 환경을 위한 sFlow 모니터링 시스템)

  • Fitriyani, Norma Latif;Kim, Jae-rin;Song, Wang-Cheol;Cho, Buseung;Kim, Sunghae
    • Proceedings of the Korea Information Processing Society Conference
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    • pp.234-237
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    • 2014
  • This paper provides insights into the sFlow monitoring system of OF@KREONET. OF@KREONET is software defined network (SDN) testbed adapted by KREONET (Korea Research Environment Open NETwork). OF@KREONET uses SDN-based network virtualization to slice the network among multiple concurrent experimenter. Flow Monitoring of OF@KREONET using sFlow. sFlow and OpenFlow can be used to provide an integrated flow monitoring system where OpenFlow controller can be used to define flows to be monitored by sFlow. OF@KREONET flow monitoring system supports monitoring of per slice FlowSpace. An Experimental can monitor his/her own FlowSpace while network administrator can monitor all spaces.

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Reactive Reserve based Contingency Constrained Optimal Power Flow to Enhance Interface Flow Limits in Terms of voltage Stability

  • Hwachang Song;Lee, Byongjun
    • KIEE International Transactions on Power Engineering
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    • v.11A no.4
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    • pp.27-32
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    • 2001
  • This paper presents a concept of reactive reserve based contingency constrained optimal power flow (RCCOPF). RCCOPF for enhancement of interface flow limit is composed of two modules, which are the modified continuation power flow (MCPF) and reactive optimal power flow (ROPF). In RCCOPF, two modules are repeatedly performed to increase interface flow margins of selected contingent states until satisfying the required enhancement of interface flow limit. In numerical simulation, a simple example with New England 39-bus test system is shown.

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