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열전달에 의한 Gas Stirred Liquid Bath 내의 유동특성에 관한 연구
최정렬,김창녕 경희대학교 산학협력기술연구원 1998 산학협력기술연구논문집 Vol.4 No.-
The flow and temperature fields in Gas Stirred Liquid Bath Systems were numerically analyzed to predict flow characteristics under the influence of heat transfer. Eulerian-Eulerian approach was used for the formulation of both the continuous and dispersed phases. Turbulence in the liquid phase was modeled using a two-equation κ-ε model. Interphase friction and heat transfer coefficients were calculated by using correlations available in the literature. The modification of the general purpose computer program PHOENICS code was employed to predict the mean flow fields, volume fraction and temperature fields. Turbulence dispersion of the phases was modeled by introducing a "dispersion Prandtl number". The calculated results were compared with experimental measurements. Quantitatively it shows very satisfactory agreement with experimental results for almost regions of ladle. The results are of interest in the design and operation of wide variety of material processing.
Choi, Choeng Ryul,Kim, Chang Nyung Ovid Technologies (Wolters Kluwer) - Lippincott Wi 2009 ASAIO journal Vol.55 No.5
<P>Bileaflet mechanical heart valves (BMHVs) are widely implanted to replace diseased heart valves but still suffer from complications such as hemolysis and platelet activation. These complications are closely related to both flow characteristics through the valves and leaflet dynamics. In this study, a fluid-structure interaction (FSI) simulation is performed to investigate the characteristics of physiological flow interacting with moving leaflets in a BMHV. The present FSI model uses both a finite volume computational fluid dynamics code and a finite element structure dynamics code to solve the governing equations for fluid flow and leaflet dynamics. In addition, a structural analysis is performed with the forces acting on the leaflet surfaces. From the analysis, detailed flow information and leaflet behavior are quantified for a cardiac cycle. The results show that the present FSI model performs well at predicting the overall flow patterns interacting with the moving leaflets and leaflet behavior in the BMHV.</P>
Choi, Choeng-Ryul,Kim, Chang-Nyung The Korean Society of Mechanical Engineers 2000 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.14 No.12
Two phase flows have been numerically calculated to analyze plume characteristics and liquid circulation in gas injection through a porous plug. The Eulerian approach has been for formulation of both the continuous and dispersed phases. The turbulence in the liquid phase has been modeled using the standard $textsc{k}$-$\varepsilon$ turbulence model. The interphase friction coefficient has been calculated using correlations available in the literature. The turbulent dispersion of the phase has been modeled by the "dispersion Prand시 number". The predicted mean flows is compared well with the experimental data. The plume region area and the axial velocities are increased with the gas flow rate and with the decrease in the inlet area. The turbulent intensity also shows the same trend. Also, the space-averaged turbulent kinetic energy for various gas flow rates and inlet areas has been obtained. The results are of interest in the design and operation of a wide variety of materials and chemical processing operations.
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.
Choi, Choeng-Ryul,Kwon, Tae-Soon,Song, Chul-Hwa Elsevier 2007 Nuclear engineering and design Vol.237 No.7
<P><B>Abstract</B></P><P>The core bypass phenomenon of borated water injected through direct vessel injection (DVI) nozzles in APR1400 (Advanced Power Reactor 1400MWe) during main steam line break (MSLB) accidents with a reactor coolant pump (RCP) running mode has been simulated using a two-channel and one-dimensional system analysis model code (MARS), and a three-dimensional computational fluid dynamics (CFD) code (FLUENT). A visualization experiment has also been performed using a scaled-down model of the APR1400. The MARS analysis has predicted a serious core bypass phenomenon of borated water, while the CFD analysis has shown results opposite to the MARS results. The CFD analysis has shown that the flow pattern in the downcomer is fully three-dimensional and that vortex flow structures are formed near the cold legs so that the borated water might pass without difficulty into the high flow region of the cold legs and flow well into the lower downcomer. The visualization experiment has shown that the borated water flows well to the lower plenum, as in the CFD analysis. Both the CFD analysis and visualization experiment have proved that a serious core bypass phenomenon of borated water might not happen in the APR1400. These results are quite different from those predicted by MARS.</P>
Choeng Ryul Choi,chang Nyung Kim,Young Joo Kwon,Jae Won Lee 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.7
Many researchers have investigated the blood flow characteristics through bileaflet mechani- cal heart valves using computational fluid dynamics (CFD) models. Their numerical approach methods can be classified into three types; steady flow analysis, pulsatile flow analysis with fixed leaflets , and pulsatile floW analysis with moving leaflets. The first and second methods have been generally employed for two-dimensional and three-dimensional calculations. The pulsatile flow analysis interacted with moving leaflets has been recently introduced and tried only in two-dimensional analysis because this approach method has difficulty in considering simulta- neously two physics of blood flow and leaflet behavior interacted with blood flow. In this publication, numerical calculation for pulsatile flow with moving leaflets using a fluid-structure interaction method has been performed in a three-dimensional geometry. Also, pulsatile flow with fixed leaflets has been analyzed for comparison with the case with moving leaflets. The calculated results using the fluid-structure interaction model have shown good agreements with results visualized by previous experiments. In peak systole, calculations with the two approach methods have predicted similar flow fields. However, the model with fixed leaflets has not been able to predict the flow fields during opening and closing phases. Therefore, the model with moving leaflets is rigorously required for advanced analysis of flow fields.
Numerical Simulation of Blood Cell Motion in a Simple Shear Flow
Choeng-Ryul Choi,Chang-Nyung Kim,Tae-Hyub Hong 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
Detailed knowledge on the motion of blood cells flowing in micro-channels under simple shear flow and the influence of blood flow is essential to provide a better understanding on the blood rheological properties and blood cell aggregation. The microscopic behavior of red blood cell (RBCs) is numerically investigated using a fluid-structure interaction (FSI) method based on the Arbitrary-Lagrangian-Eulerian (ALE) approach and the dynamic mesh method (smoothing and remeshing) in FLUENT ( ANSYS Inc., USA). The employed FSI method could be applied to the motions and deformations of a single blood cell and multiple blood cells, and the primary thrombogenesis caused by platelet aggregation. It is expected that, combined with a sophisticated large-scale computational technique, the simulation method will be useful for understanding the overall properties of blood flow from blood cellular level (microscopic) to the resulting rheological properties of blood as a mass (macroscopic).