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냉방 모드에 대한 승용차 탑승부 내의 유동해석에 관한 연구
이공희(G.H.Lee),박준영(J.Y.Park),백제현(J.H.Baek) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.11_1
For the purpose of designing an effective air-conditioner, the flows in a vehicle passenger compartment have been simulated by the numerical analysis with a standard k - ε turbulence model. The effect of changing the direction and magnitude of an inlet velocity on the interior flow configuration was investigated. Comparisons are made with the published experimental and computational results, giving a good qualitative consistency.<br/>
설계조건에서 선형 익렬의 익단 간극 크기가 익단 간극 누설유동에 미치는 영향에 관한 수치해석
이공희(G.H. Lee),배준호(J.H. Bae) 한국전산유체공학회 2018 한국전산유체공학회지 Vol.23 No.4
A steady-state Reynolds averaged Navier-Stokes simulations was conducted to investigate the effect of tip clearance size on the distribution of tip leakage flow inside a linear cascade. Two different tip clearance size, t=2 mm and 4 mm, were considered under design condition(i.e. inlet flow angle β = 29.3°). As the tip clearance increased, the gradient of the static pressure trough at the endwall became larger and the tip leakage flow rolled-up more strongly in a helical form. In addition, high total pressure loss region corresponding to the distribution of tip leakage vortex was somewhat enlarged in the downstream positions of the blade trailing edge. The flow rate through the tip clearance increased in proportion to tip clearance size, and as a result, the swirling flow became stronger, so that the center of tip leakage vortex moved more from the blade tip to the hub. Additionally, the region with high turbulent intensity where the leakage flow exited the tip clearance in the form of jet, was extended to the inside of the flow path along the endwall. Finally, it was confirmed that there were several indicators to confirm the existence of tip leakage vortex. The defect of axial velocity in the tip region of blade flow path, the dimensionless helicity with a magnitude close to 1, the endwall pressure trough, the region with high total pressure loss, and strong roll-up of the particle trajectory were the typical examples. By taking these indicators as a comprehensive consideration, the existence of tip leakage vortex can be effectively found.
직경비 크기가 평판 오리피스 유량계 주위의 유동 형태에 미치는 영향에 관한 수치적 연구
이공희(G.H. Lee),배준호(J.H. Bae) 한국전산유체공학회 2019 한국전산유체공학회지 Vol.24 No.3
At present, domestic nuclear power plants are carrying out In-Service Test (IST) to check safety functions of safety-related pumps and monitor/evaluate the degree of vulnerability over time during reactor operation. When performing this pump IST, it is necessary to measure the differential pressure at the test flow rate indicated on the differential pressure type flowmeter, and check whether the corresponding differential pressure magnitude meets the acceptance criteria. Therefore, it is necessary to confirm whether a differential pressure type flowmeter, such as a flat orifice flowmeter, indicates the correct flow rate under wide operating conditions. In addition, depending on the ratio of pipe diameter to orifice hole diameter, the flow pattern around an orifice flowmeter may be changed, and measurement uncertainty for flow rate or pressure loss magnitude may be affected. Therefore, the selection of proper diameter ratio is essential for the orifice flowmeter design. In this study, the effect of diameter ratio magnitudes (0.5 and 0.75) on the flow pattern around a flat orifice flowmeter was investigated by using the commercial computational fluid dynamics software ANSYS CFX R18.1.
이공희(G. H. Lee),백제현(J. H. Baek) 한국전산유체공학회 1999 한국전산유체공학회지 Vol.4 No.1
This paper describes a numerical method for predicting the incompressible unsteady laminar three-dimensional flows with free-surface. The Navier-Stokes equations governing the flows have been discretized by means of finite-difference approximations, and the resulting equations have been solved via the SIMPLE-C algorithm. The free-surface is defined by the motion of a set of marker particles and the interface behaviour was investigated by means of a "Lagrangian" technique. Using the GALA concept of Spalding, the conventional mass continuity equation is modified to form a volumetric or bulk-continuity equation. The use of this bulk-continuity relation allows the hydrodynamic variables to be computed over the entire flow domain including both liquid and gas regions. Thus, the free-surface boundary conditions are imposed implicitly and the problem formulation is greatly simpJjfjed. The numerical procedure is validated by comparing the predicted results of a periodic standing waves problems with analytic solutions. The results show that this numerical method produces accurate and physically realistic predictions of three-dimensional free-surface flows.
수직축을 중심으로 회전하는 직관과 정지한 곡관 내부의 발달하는 층류 유동의 유사성에 관한 수치적 연구
이공희(G. H. Lee),백제현(J. H. Baek) 한국전산유체공학회 2001 한국전산유체공학회지 Vol.6 No.1
A numerical study on the similarity of the developing laminar flows between in a straight duct rotating about an axis perpendicular to that of the duct and in a stationary curved duct Was carried out. In order to clarify the analogy of two flows, dimensionless parameters KLR = Re/√Ro and Rossby number, λ, in a rotating straight duct were used as a set corresponding to Dean number, KLC'=Re/√λ, and curvature ratio, A, in a stationary curved duct. For the large values of Ro and λ, it is shown that the flow field satisfies the 'asymptotic invariance property', that is, there are strong quantitative similarities between the two flows such as flow patterns, friction factors, and maximum axial velocity magnitudes for the same values of KLR and KLC if they are correlated with dimensionless axial distances ZR= z/(d√Ro) for a rotating duct flow and Zc=z/(d√λ) for a stationary curved duct flow.
이공희(G. H. Lee),백제현(J. H. Baek) 한국전산유체공학회 1999 한국전산유체공학회지 Vol.4 No.1
This paper describes a numerical method for predicting the incompressible unsteady laminar three-dimensional flows with free-surface. The Navier-Stokes equations governing the flows have been discretized by means of finite-difference approximations, and the resulting equations have been solved via the SIMPLE-C algorithm. The free-surface is defined by the motion of a set of marker particles and the interface behaviour was investigated by means of a Lagrangian technique. Using the GALA concept of Spalding, the conventional mass continuity equation is modified to form a volumetric or bulk-continuity equation. The use of this bulk-continuity relation allows the hydrodynamic variables to be computed over the entire flow domain including both liquid and gas regions. Thus, the free-surface boundary conditions are imposed implicitly and the problem formulation is greatly simpJjfjed. The numerical procedure is validated by comparing the predicted results of a periodic standing waves problems with analytic solutions. The results show that this numerical method produces accurate and physically realistic predictions of three-dimensional free-surface flows.
이공희(G. H. Lee),백제현(J. H. Baek) 한국전산유체공학회 1998 한국전산유체공학회 학술대회논문집 Vol.1998 No.-
This describes a numerical method for predicting the incompressible unsteady laminar three-dimensional flows of fluid behaviour with free-surface. The elliptic differential equations governing the flows have been linearized by means of finite-difference approximations, and the resulting equations have been solved via a fully-implicit iterative method. The free-surface is defined by the motion of a set of marker particles and interlace behaviour was investigated by way of a "Lagrangian" technique. Using the GALA concept of Spalding. the conventional mass continuity equation is modified to farm a volumetric or bulk-continuity equation. The use of this bulk-continuity relation allows the hydrodynamic variables to be computed over the entire flow domain including both liquid and gas regions, Thus, the free-surface boundary conditions are imposed implicitly and the problem formulation is greatly simplified. The numerical procedure is validated by comparing the predicted results of a periodic standing waves problems with analytic solutions or experimental results from the literature. The results show that this numerical method produces accurate and physically realistic predictions of three-dimensional free-surface flows.