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최청렬,김창녕,Choi, Choeng Ryul,Kim, Chang Nyung 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.10
Characteristics of two-phase flow and heat transfer were numerically investigated in a submerged gas Injection system. Effects of both the gas flow rate and bubble size were investigated. In addition, heat transfer characteristic and effects of heat transfer were investigated when temperature of the injected gas was different from that of the liquid. The Eulerian approach was used for the formulation of both the continuous and the dispersed phases. The turbulence in the liquid phase was modeled by the use of the standard $k-{\varepsilon}$ turbulence model. The interphase friction and heat transfer coefficient were calculated by means of correlations available in the literature. The turbulent dispersion of the phases was modeled by introducing a "dispersion Prandtl number". The plume region and the axial velocities are increased with increases in the gas flow rate and with decreases in the bubble diameter. The turbulent flow field grows stronger with the increases in the gas flow rate and with the decreases in the bubble diameter. In case that the heat transfer between the liquid and the gas is considered, the axial and the radial velocities are decreased in comparison with the case that there is no temperature difference between the liquid and the gas when the temperature of the injected gas is higher than the mean liquid temperature. The results in the present research are of interest in the design and the operation of a wide variety of material and chemical processes.
판막 거동을 고려한 이엽 기계식 인공심장 판막에서의 맥동유동에 관한 수치해석
최청렬(Choeng-Ryul Choi),김창녕(Chang-Nyung Kim) 한국유체기계학회 2002 유체기계 연구개발 발표회 논문집 Vol.- No.-
Bileaflet mechanical valves have the complications such as hemolytic and thromboembolic events, leaflet damage, and leaflet break. These complications are related with the fluid velocity and shear stress characteristics of mechanical heart valves. This fact makes clear the importance of determining the fluid velocity and shear stress characteristics of mechanical heart valves, and requires a detailed understanding of these system properties and further substantial research.<br/> The first aim of current study is to introduce fluid-structure interaction method for calculation of unsteady and three-dimensional blood flow through bileaflet valve and leaflet behavior interacted with its flow, and to overcome the shortness of previous studies, where the leaflet motion has been ignored or simplified, by using FSI method. To accomplish this goal, a finite volume computational fluid dynamics code and a finite element structure dynamics code have been used concurrently to solve the flow and structure equations, respectively, to investigate the interaction between the blood flow and leaflet.<br/> Physiologic ventricular and aortic pressure waveforms were prescribed as flow boundary conditions. The interaction of aortic flow and valve motion were computed.
Direct numerical simulations on the migration of particles in tube flow
Choeng Ryul Choi(최청렬),Chang Nyung Kim(김창녕),Yong Jun An(안용준) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The cross-stream migration of a single neutrally buoyant rigid particle in tube flow is simulated by a direct numerical simulation. Numerical experiments using the method of constrained simulation generate data for the lift force and velocities of a freely rotating sphere in steady flows arising from initial-value problems in which the sphere is constrained to move at a fixed radius. The simulations give results in good agreement with previous results. Constrained simulations are very efficient. The lift and all velocities are obtained for different radii at each specified Reynolds number. The equilibrium position (the Segre?Silberberg radius) moves towards the wall as Re increases at each fixed radius.
최청렬,김창녕 慶熙大學校 大學院 院友會 1999 高凰論集 Vol.24 No.-
Characteristics of two-phase flow and heat transfer were numerically investigated in gas injected reactors. Heat transfer characteristic and effects of heat transfer were investigated when temperature of the injected gas is different from that of the liquid. The Eulerian approach was used for the formulation of both the continuous and dispersed phases. The turbulence in the liquid phase was modeled by the use of the standard κ-ε turbulence model. The interphase friction and heat transfer coefficient were calculated by means of correlations available in the literature. The turbulent dispersion of the phases was modeled in introducing a "dispersion Prandtl number". The results in the present research are of interest in the design and operation of a wide variety of material and chemical processes.