• Journal of Korean Society of Environmental Engineers
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• v.33 no.4
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• pp.251-257
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• 2011

In the present study, a 3-dimensional (3D) numerical model was developed to mimic the micro porous structure of a geological $CO_2$ storage reservoir. Especially, 3D modeling technique assigning random pore size to a 3D micro porous structure was devised. Numerical method using CFD (computational fluid dynamics) was applied for the 3D micro porous structure to calculate supercritical $CO_2$ flow field. The three different configurations of 3D micro porous model were designed and their flow fields were calculated. For the physical conditions of $CO_2$ flow, temperature and pressure were set up equivalent to geological underground condition where $CO_2$ fluid was stored. From the results, the characteristics of the supercritical $CO_2$ flow fields were scrutinized and the influence of the micro pore configuration on the flow field was investigated. In particular, the pressure difference and consequent $CO_2$ permeability were calculated and compared with increasing $CO_2$ flow rate.

• Journal of Korea Water Resources Association
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• v.45 no.3
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• pp.331-347
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• 2012

The downstream of the Nam River Dam is crucial region for long-term water resource planning for Busan and Gyeongnam Province. Thus, the analysis of flow behavior and water quality is necessary for the sustainable surface water management and the control of pollutant source. In this study, the flow field and BOD transport at the downstream of Nam River Dam were analyzed by incorporating 2-D water quality model, RAM4 and 3-D water quality model, WASP with the hydrodynamic model, RAM2 and EFDC, respectively. The application of 2-D flow analysis model, RAM2 showed that velocity distributions at the five transverse sections of the meandering part closely followed the measured values by ADCP, and the flow field and overflow characteristic at the submerged weir showed satisfactory performance compared with the result of 3-D EFDC model. In addition, the BOD concentration field obtained by RAM2-RAM4 coupled modeling was in good agreement with the result by EFDC-WASP model throughout the computational domain. The hydrodynamic characteristic and water quality at the downstream reach of Nam River Dam are mainly influenced by the Dam discharge, and the water quantity is closely related to the water quality control and fishery environment at the lower part of Nakdong River. Therefore, when further quantitative analysis is necessary regarding these issues, 2-D semi-coupled modeling is recommended in terms of computational effectiveness and model application aspect.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.2
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• pp.10-19
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• 2009

The working of diesel particulate filters(DPF) needs to periodically burn soot that has been accumulated during loading of the DPF. The prediction of the relation between an uniformity of gas velocity and soot regeneration efficiency with simulations helps to make design decisions and to shorten the development process. This work presents a comprehensive combined 'DOC+CDPF' model approach. All relevant behaviors of flow fluid are studied in a 3D model. The obtained flow fields in the front of DPF is used for 1D simulation for the prediction of the thermal behavior and regeneration efficiency of CDPF. Validation of the present simulation are performed for the axial and radial direction temperature profile and shows goods agreement with experimental data. The coupled simulation of 3D and 1D shows their impact on the overall regeneration efficiency. It is found that the flow non-uniformity may cause severe radial temperature gradient, resulting in degrading regeneration efficiency.

• The KSFM Journal of Fluid Machinery
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• v.18 no.1
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• pp.44-50
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• 2015

Labyrinth seals are commonly used in various kinds of turbomachinery to reduce leakage flow. In the present 3D CFD analysis of see-through-type labyrinth air seal, the methodology of determining leakage and rotordynamic coefficients is suggested with the relative coordinate system for steady-state simulation. The leakage flow and rotordynamic forces predicted by using different solvers and turbulent models of FLUENT are compared with the results of the existing bulk-flow analysis code LABYSEAL.FOR and experiment. The present CFD result of direct stiffness(K) shows only improvement in prediction. The results of leakage and rotordynamic coefficients as well as computing time are sensitive against the used solver and turbulent model.

• Particle and aerosol research
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• v.9 no.3
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• pp.163-171
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• 2013

Soot particles emitted from combustion processes are often coated by non-absorbing organic materials, which enhance the global warming effect of soot particles. It is of importance to study the condensation characteristics of soot particles experimentally and theoretically to reduce the uncertainty of the climate impact of soot particles. In this study, the condensational growth of soot particles in a tubular coater was modeled by a one-dimensional (1D) plug flow model and a two-dimensional (2D) laminar flow model. The effects of 2D heat and mass transports on the predicted particle growth were investigated. The temperature and coating material vapor concentration distributions in radial direction, which the 1D model could not accounted for, affected substantially the particle growth in the coater. Under the simulated conditions, the differences between the temperatures and vapor concentrations near the wall and at the tube center were large. The neglect of these variations by the 1D model resulted in a large error in modeling the mass transfer and aerosol dynamics occurring in the coater. The 1D model predicted the average temperature and vapor concentration quite accurately but overestimated the average diameter of the growing particles considerably. At the outermost grid, at which condensation begins earliest due to the lowest temperature and saturation vapor concentration, condensing vapor was exhausted rapidly because of the competition between condensations on the wall and on the particle surface, decreasing the growth rate. At the center of the tube, on the other hand, the growth rate was low due to high temperature and saturation vapor concentration. The effects of Brownian diffusion and thermophoresis were not high enough to transport the coating material vapor quickly from the tube center to the wall. The 1D model based on perfect radial mixing could not take into account this phenomenon, resulting in a much higher growth rate than what the 2D model predicted. The result of this study indicates that contrary to a previous report for a thermodenuder, 2D heat and mass transports must be taken into account to model accurately the condensational particle growth in a coater.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.4
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• pp.363-371
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• 2008

The aim of this study is to compare the numerical results obtained by 2-D and 3-D models which are used to examine the wave field around a permeable submerged breakwater. At first, the numerical model, which is able to consider the flow through a porous medium with inertial, laminar and turbulent resistance terms and determine the eddy viscosity with LES turbulent model, is used and validated by comparing with existing experimental data. And then, the numerical test on the wave field around a permeable submerged breakwater is performed. It is revealed from the numerical results that, at the onshore side of the submerged breakwater, the wave height by 2-D analysis is higher than that by 3-D analysis. Also, the time-averaged mean flow around a submerged breakwater is discussed in detail.

• Journal of computational fluids engineering
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• v.8 no.2
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• pp.49-56
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• 2003

Three-dimensional endwall flow within a linear cascade passage of high performance turbine blade is simulated with a 3-D Navier-Stokes CFD code (MOSA3D), which is based on body-fitted coordinate system, pressure-correction and finite volume method. The endwall flow characteristics, including the development and generation of horseshoe vortex, passage vortex, etc. are clearly simulated, consistent with the generally known tendency. The effects of both turbulence model and convective differencing scheme on the prediction performance of endwall flow are systematically analyzed in the present paper. The convective scheme is found to have stronger effect than the turbulence model on the prediction performance of endwall flow. The present simulation result also indicates that the suction leg of the horseshoe vortex continues on the suction side until it reaches the trailing edge.

• Journal of computational fluids engineering
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• v.8 no.3
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• pp.1-6
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• 2003

Three-dimensional endwall flow within a linear cascade passage of high performance turbine blade is simulated with a 3-D Wavier-Stokes CFD code (MOSA3D), which is based on body-fitted coordinate system, pressure-correction and finite volume method. the endwall flow characteristics, including the development and generation of horseshoe vortex, passage vortex, etc. are clearly simulated, consistent with the generally known tendency The effects of both turbulence model and convective differencing scheme on the Prediction performance of endwall flow are systematically analyzed in the present paper. The convective scheme is found to have stronger effect than the turbulence modei on the prediction performance of endwall flow. The present simulation result also indicates that the suction leg of the horseshoe vortex continues on the suction side until it reaches the trailing edge.

• Journal of computational fluids engineering
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• v.8 no.1
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• pp.8-15
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• 2003

Three-dimensional endwall flow within a linear cascade passage of high performance turbine blade is simulated with a 3-D Wavier-Stokes CFD code (MOSA3D), which is based on body-fitted coordinate system, pressure-correction and finite volume method. The endwall flow characteristics, including the development and generation of horseshoe vortex, passage vortex, etc. are clearly simulated, consistent with the generally known tendency. The effects of both turbulence model and convective differencing scheme on the prediction performance of endwall flow are systematically analyzed in the present paper. The convective scheme is found to have stronger effect than the turbulence model on the prediction performance of endwall flow. The present simulation result also indicates that the suction leg of the horseshoe vortex continues on the suction side until it reaches the trailing edge.

• Journal of computational fluids engineering
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• v.20 no.3
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• pp.1-7
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• 2015

When the steam is used as working fluid in fluid machinery, different from other gases as air, phase transition (steam condensation) can occur and it affects not only the flow fields, but also machine performance & efficiency. Therefore, considering phase transition phenomena in CFD calculation is required to achieve accurate prediction of steam flow and non-equilibrium wet-steam model is needed to simulate realistic steam condensing flow. In this research, non-equilibrium wet-steam model is implemented on in-house code(T-Flow), the flow fields including phase transition phenomena in convergent-divergent nozzle are studied and compared to results of advance researches.