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집중시스템 모델을 이용한 이중박동 생명보조장치 작동하의 관상순환계 반응해석
고형종(Hyung-Jong Ko),박종천(Jong-Cheon Park),심은보(Eun-Bo Shim) 한국산업융합학회 2009 한국산업융합학회 논문집 Vol.12 No.1
In this paper, a computational analysis using a lumped system model is performed to investigate the hemodynamics of coronary circulation under the operation of T-PLS relevant to the cardiac arrest cases. The coronary circulation system is assumed to be comprised of three compartments: coronary arteries, coronary capillaries, and coronary veins. The effect of myocardial muscle contraction or relaxation is represented by temporal variations in the bias pressure. To verify the present method, we analyzed the coronary circulation for normal case and then compared the results with the existing data. Numerical results on the cardiac arrest model showed that T-PLS can increase LAD flow significantly.
균일 두께의 자성유체 피막이 있는 평면 벽을 향하는 2차원 정체 유동
고형종(Hyung-Jong Ko),김경훈(Kyoung-Hoon Kim),김세웅(Se-Woong Kim) 한국전산유체공학회 2007 한국전산유체공학회지 Vol.12 No.4
Two-dimensional stagnation flow toward a plane wall coated with magnetic fluid of uniform thickness is investigated. The flow field is represented as a similarity solution of the Navier-Stokes equation for this incompressible laminar flow. The resulting third order ordinary differential equation is solved numerically by using the shooting method and by determining two shooting parameters so as to satisfy the boundary and interface conditions. Features of the flow including streamline patterns are investigated for the varying values of density ratio, viscosity ratio, and Reynolds number. An adverse flow with double eddy pair in magnetic fluid region is found to emerge as the Reynolds number becomes higher than a threshold value. The results for the interface velocity, interface and wall shear stress, and boundary layer and displacement thickness are also presented.
균일 두께로 자성유체가 피막된 평면 벽 주위의 축대칭 정체 유동
고형종(Hyung-Jong Ko),김경훈(Kyoung-Hoon Kim),김세웅(Se-Woong Kim) 한국전산유체공학회 2007 한국전산유체공학회 학술대회논문집 Vol.2007 No.-
A similarity solution of the Navier-Stokes equation for the axisymmentric stagnation flow near a plane wall coated with a magnetic fluid of uniform thickness is constructed. The shape functions representing the flow in two(magnetic and normal) fluid layer are determined from a third order boundary value problem, which is solved by the Runge-Kutta method with two shooting parameters. Features of the flow including streamline pattern and interface velocity are investigated for the varying values of density ratio, viscosity ratio, and Reynolds number. The results for the interface and wall shear stress, boundary layer and displacement thickness are also presented.
발사대기 중인 액체추진 로켓의 극저온 산화제 탱크 내 비정상 열해석
김경훈(Kyoung Hoon Kim),고형종(Hyung-Jong Ko),김경진(Kyoungjin Kim),조기주(Kie-Joo Cho),오승협(Seung-Hyub Oh) 한국추진공학회 2008 한국추진공학회지 Vol.12 No.4
The prelaunch thermal transients in the cryogenic oxidizer tank of liquid propulsion rocket subjected to uniform heat flux from outside are numerically analyzed through thermodynamic equations and heat and mass transfer relations. The prelaunch stage is assumed to be composed of five idealized sub-stages including pressurization process by helium gas injection. The Peng-Robinson equation of state is utilized in the lumped analysis of ullage gas. The liquid region is divided into a number of horizontal layers of uniform properties to account for the thermal stratification. The computational result for the typical case shows that the temperature rise of liquid oxidizer is less than 1K and the adsorbed helium into the liquid is approximately 10g.
압축기 출구 물분사가 있는 재생 가스터빈 시스템의 엑서지 해석
김경훈(Kyoung-Hoon Kim),고형종(Hyung-Jong Ko),김세웅(Se-Woong Kim) 한국산업융합학회 2010 한국산업융합학회 논문집 Vol.13 No.1
An exergy analysis is carried out for the regenerative gas turbine cycle which has a potential of enhanced thermal efficiency and specific power owing to the more possible water injection than that of inlet fogging under the ambient conditions. Using the analysis model in the view of the second law of thermodynamics, the effects of pressure ratio, water injection ratio and ambient temperature are investigated on the performance of the system such as exergetic efficiency, heat recovery ratio of recuperator, exergy destruction or loss ratios, and on the optimal conditions for maximum exergy efficiency. The results of computation for the typical cases show that the regenerative gas turbine system with afterfogging can make a notable enhancement of exergy efficiency.
정호열(Ho-Eyoul Jeong),정재택(Jae-Tack Jeong),고형종(Hyung-Jong Ko) 한국전산유체공학회 1999 한국전산유체공학회 학술대회논문집 Vol.1999 No.-
There have been many studies for heat transfer enhancement. Particularly, the study of flow in heat exchangers which have fin device has been main theme in heat transfer area. Practically, the circular tube which has internal fins is widely used for developing heat transfer rate. In this study, flow and heat transfer analysis of the circular tube with fins are investigated. The height and the number of fins are arbitrary. The flow field is assumed to be laminar. The conform mapping is used for analytic solution of the laminar flow field. Discretization of governing equation, namely, FDM was used for numerical analysis. The velocity field, flow rate and shear stress are calculated for some numbers of fins in circular tube and for some heights of fin. Temperature fields are plotted along the tube length. It can be shown that the numerical solution agrees with the analytical solution.
압축기 출구 물분사가 있는 재생 가스터빈 시스템의 성능해석
김경훈(Kyoung Hoon Kim),김세웅(Se Woong Kim),고형종(Hyung-Jong Ko) 대한설비공학회 2009 설비공학 논문집 Vol.21 No.8
A performance analysis of the regenerative gas turbine system with afterfogging is carried out. Because of the high temperature at the outlet of air compressor, afterfogging has a potential of improved recuperation of exhaust heat than inlet fogging. Thermodynamic analysis model of the gas turbine system is developed by using an ideal gas assumption. Using the model, the effects of pressure ratio, water injection ratio, and ambient temperature are investigated parametrically on thermal efficiency and specific power of the cycle. The dependency of pressure ratio giving peak thermal efficiency is also investigated. The results of numerical computation for the typical cases show that the regenerative gas turbine system with afterfogging can make a notable enhancement of thermal efficiency and specific power. In addition, the peak thermal efficiency is shown to decrease almost linearly with ambient temperature.
혈관계 시스템 모델과 CFD의 결합을 통한 관상동맥 내 혈류의 수치적 해석
심은보(Eun Bo Shim),박명수(Myung Soo Park),고형종(Hyung Jong Ko),김경훈(Kyung Hoon Kim) 한국전산유체공학회 1999 한국전산유체공학회 학술대회논문집 Vol.1999 No.-
For the simulation of the blood flow in coronary artery, the system modeling of coronary hemodynamics is combined with CFD technique. The blood flow in coronary artery interacts with the global coronary circulation. Especially in case of the coronary artery with stenosis, the interaction plays an important role in the hemodynamics of the circulation. In this study we present a combined numerical approach using both the CFD technique for flow simulation and the global system model of coronary circulation. We use a lumped parameter model for the global simulation of coronary circulation whereas the finite element method is employed to compute the viscous flow field in stenosed coronary artery. The time variation of the pressure drop due to stenosis is obtained from the proposed numerical method. Numerical results shows that the flow resistance and pressure drop due to stenosis has a relatively large value in systole.