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핵연료봉 주위에 형성되는 난류유동장에서 부수로 압력손실에 대한 해석적 연구
이계복,벽면마찰속도,Lee, Kye Bock 대한기계학회 1995 대한기계학회논문집 Vol.19 No.10
A theoretically based prediction for the determination of the subchannel friction factor at low pitch to the rod diameter ratio (P/D < 1.2) in the bare rod bundle flow has been developed. The present model assumes the validity of the Law of Wall over the entire flow area. The algebraic form of the Law of the Wall is integrated over the entire flow area and the local friction velocity variation along the rod periphery is considered in this study. The present method is applied to the rod bundles with P/D < 1.2, and the prediction results show good agreement with the available experimental data.
이계복 ( Kye Bock Lee ),조용 ( Yong Cho ) 충북대학교 건설기술연구소 2014 建設技術論文集 Vol.33 No.1
항구로 바닷물이 들어올 때 수문개도와 수위차에 따른 수문하부의 유동특성과 자려진동을 2차원 비정상 상태로 수치적으로 해석하였다. 진동수에 대한 결과는 수문아래의 외류에 의해 발생하였다. 수문 하부에서 발생하는 역류와 전단력, 와유출 등의 유동특성을 분석하였고 수문 개도가 증가할수록, 진동수는 감소하였다. 수문의 고유진동수에 근접하는 수위차와 수문개도의 유동조건을 예측하였다. The goal of the present work is to investigate the flow characteristics under the water gate and the flow induced vibration by 2-dimensional unsteady CFD simulation for different opening gaps of the water gate and the wawter level differences. The flow characteristics such as velocity profile. shear stress and vortex shedding under the water gate are analyzed. As the gate opening gap increases, the oscillated frequency decreases. The prediction results show the dangerous operating conditions on the gate opening gap and the water level difference which could be resonant.
다상모델을 이용한 탁도계 버블트랩 내부 유동장에 관한 고찰
이계복(Kye-Bock Lee),김영도(Young-Do Kim) 대한기계학회 2007 大韓機械學會論文集B Vol.31 No.11
The objectives of this study are to examine a bubble trap mechanism of the turbidimeter for low turbidity and to acquire it's technology concerned. Reynolds-Averaged Navier-Stokes equation and Laglangian discrete phase model were applied to analyze a flow field in the bubble trap. 3D hybrid grid system was used to simulate the flow field of bubble trap and numbers of it's node point are about 110,000. From the comparison between the standard k- ε model and the laminar state, it was found that the former estimated less the velocity in the outlet of bubble trap than the latter did, and that the former estimated more the shear stress at the wall of bubble trap than the latter did. And, it was possible to visualize the path of bubbles in the bubble trap and to copy the removal process of bubbles out bubble trap. Also, it was found that nearly most of bubbles in the bubble trap disappeared.
가열된 평판에서 원형 충돌제트의 열전달에 미치는 난류유동 특성의 영향
이계복 ( Kye Bock Lee ),윤지환 ( Ji Hwan Yun ) 충북대학교 산업과학기술연구소 2009 산업과학기술연구 논문집 Vol.23 No.1
An experimental study of jet impingement on the surface with linear temperature gradient is conducted with the presentation of the turbulent characteristics and the heat transfer rates measured when this jet impinges normal to a flat plate. The jet Reynolds number ranges from 10,000 to 70,000, the temperature gradient of the plate is 1.6~4.4 ℃ /cm and the dimensionless nozzle to plate distance(H/D) is from 4 to 12. The results show that the peak of heat transfer rate occurs at the stagnation point, and the heat transfer rate decreases as the radial distance from the stagnation point increases. A remarkable feature of the heat transfer rate is the existence of the second peak. This is due to the turbulent development of the wall jet. Maximum heat transfer rate occurs when the axial distance from the nozzle to nozzle diameter(H/D) is 6 or 8. It has been found that the heat transfer rate increases with increasing turbulent intensity. The numerical analysis using the CFD package FLUENT is executed to compare the experimental results and to find out whether the CFD package can be adopt for the design of impinging jet. CFD satisfactorily predicted performance of jet impingement.
유체기구를 이용한 유압계통의 충격치제어에 수탄되는 반응지연에 관한 연구
이주성,이계복,Lee, Joo-Seong,Lee, Kye-Bock 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.11
The response time represents how fast a system responds to a given disturbance at the system boundary. Flow restricting devices for controlling transients can result in a decrease in the peakm pressure, but may change response time. Response lag in a hydraulic system leads to inefficient working cycle and operator discomfort. The experiments were conducted in order to get information on the parameters which exert appreciable influence on the response time. The experimental apparatu including a hydraulic actuator, orifice and a hydraulic pump was an idealization of a bucket hydraulic shifting system. Experimental results show that the response time depends on operating pressure and flow rate. The effects of orifice type and size on the response time are quantified.
고체입자가 부상된 이상유동에서 운반유체의 난류강도에 대한 해석적 접근
김세윤,이충구,이계복,Kim, Se-Yun,Lee, Chung-Gu,Lee, Kye-Bock 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.6
The purpose of this research is to develop the model of turbulence modulation due to the presence of particles in various types of particle-laden flows Available experimental data are surveyed and the dependence of turbulence modulation of carrier-phase on particle size, concentration and. particle Reynolds number are examined. This study takes into account the effect of wake produced by particle, the drag between phases and the velocity gradient in the wake to estimate the production of turbulence. The model of turbulence modulation using the mixing length theory under the assumption of equilibrium flow is proposed. Numerical results show that the model is successful in predicting the characteristics of the particle-laden in various flow conditions both qualitatively and quantitatively.
송의혁 ( Eui-hyeok Song ),이계복 ( Kye-bock Lee ) 충북대학교 산업과학기술연구소 2020 산업과학기술연구 논문집 Vol.34 No.1
Recently, as interest in the environment has increased, electric vehicles instead of fossil fuel vehicles have been increasingly used to reduce global warming or exhaust gas pollution. Inside the electric vehicle, battery cells are built-in, and each battery cell generates heat, causing performance degradation and failure. Therefore, a cooling system is needed to cool this heat. In particular, heat pipes show efficient performances for cooling electronic equipment. Heat transfer through the phase change of the working fluid contained in the heat pipe chamber is very fast. The heat pipes have various thermal characteristics depending on the shape of the chamber, porosity of the wick, and filling ratio of the working fluid. In this study, the thermal performance of the heat pipe are calculated through computational fluid dynamics(CFD) by modeling heat pipes and applying boundary conditions. The prediction results show the velocity distribution, temperature distribution, condensation and evaporation phenomena inside the heat pipe and makes them available for future heat pipe research.
소수력 발전용 횡류수차의 최적설계를 위한 유동장 수치해석
임태은 ( Tae Eun Lim ),이계복 ( Kye Bock Lee ),정규원 ( Kyu Won Jeong ) 충북대학교 산업과학기술연구소 2010 산업과학기술연구 논문집 Vol.24 No.2
The CFD code is commonly used in many fields to reduce the cost and time of designing a product. Hydro-power attracts increasing attention in point of the effective use of water resources and it occupied as the circular energy system. The numerical study was conducted to find the optimal design of a cross flow turbine. In this paper several simple models were designed from the inlet nozzle to the outlet nozzle for numerical analysis of small sized cross flow turbine. For the analysis the Gambit was used and each model was composed of approximately 130,000 non-uniform grids. Solutions are conducted for the velocity distribution, velocity magnitude, internal flow, hydraulic characteristics for the cross flow turbine.