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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of computational fluids engineering
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Journal DOI :
Korea Society of Computational Fluids Engineering
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Volume & Issues
Volume 12, Issue 4 - Dec 2007
Volume 12, Issue 3 - Sep 2007
Volume 12, Issue 2 - Jun 2007
Volume 12, Issue 1 - Mar 2007
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WIND PRESSURE TRANSIENTS ON PLATFORM SCREEN DOOR OF SIDE PLATFORMS IN A SUBWAY STATION CAUSED BY PASSING TRAINS
Lee, Myung-Sung ; Lee, Sang-Hyuk ; Hur, Nahm-Keon ;
Journal of computational fluids engineering, volume 12, issue 4, 2007, Pages 1~6
In the present study, the wind pressure transients on platform screen door in side platforms caused by passing trains have been investigated numerically. The transient compressible 3-D full Navier-Stokes solution is used with actual operational condition of subway train by adopting the moving mesh technique considering the train movement. To achieve more accurate analysis, the entrance and exit tunnel connecting the stations are included in a computational domain with modeling the detailed shape of the train. Numerical analyses are conducted on five operational conditions which include the variation of the train speed, case with or without the train stopped in the other track, and case for two trains passing each other inside the station. The results show that pressure load on platform screen door is maximized when the two trains are passing each other. It is also seen from the computational results that the maximum pressure variation for the cases considered in the present study is found to be satisfactory to various foreign standards.
NUMERICAL STUDY ON COMBINED HEAT TRANSFER IN NIR HEATING CHAMBER
Choi, H.K. ; Yoo, G.J. ; Kim, I.H. ;
Journal of computational fluids engineering, volume 12, issue 4, 2007, Pages 7~13
Numerical analysis is carried out for combined heat transfer in an indirected NIR(Near Infrared Ray) heating chamber. Reynolds number and shapes of absorbed cylinder are known as important parameters on the combined heat transfer effects. Reynolds number based on the outer diameter of the cylinder is varied from
. Four difference heat transfer regimes are observed: forced convection and radiative heat transfer on the outer surface of the cylinder, pure conduction in the cylinder body, pure natural convection and radiation between lamp surface and inner surface of the cylinder, and radiation from the lamp. Flow and temperature characteristics are presented with iso-contour lines for the absorbed circular and elliptic cylinders to compare their differences. The convective and radiative heat transfer fluxes are also compared with different Reynolds numbers. As usual, Reynolds number is an important factor to estimate increasing convective heat transfer as it increases. The shape of absorbed cylinder results overall heat transfer rates remain unchanged.
DEVELOPMENT OF A NUMERICAL TECHNIQUE FOR CAPILLARY SPREADING OF A DROPLET CONTAINING PARTICLES ON THE SOLID SUBSTRATE
Hwang, Wook-Ryol ; Jeong, Hyun-Jun ; Kim, See-Jo ; Kim, Chong-Youp ;
Journal of computational fluids engineering, volume 12, issue 4, 2007, Pages 14~19
We present a direct numerical simulation technique and some preliminary results of the capillary spreading of a droplet containing particles on the solid substrate. We used the level-set method with the continuous surface stress for description of droplet spreading with interfacial tension and employed the discontinuous Galerkin method for the stabilization of the interface advection equation. The distributed Lagrangian-multipliers method has been combined for the implicit treatment of rigid particles. We investigated the droplet spreading by the capillary force and discussed effects of the presence of particles on the spreading behavior. It has been observed that a particulate drop spreads less than the pure liquid drop. The amount of spread of a particulate drop has been found smaller than that of the liquid with effectively the same viscosity as the particulate drop.
TWO-DIMENSIONAL STAGNATION FLOW TOWARD A PLANE WALL COATED WITH MAGNETIC FLUID OF UNIFORM THICKNESS
Ko, Hyung-Jong ; Kim, Kyoung-Hoon ; Kim, Se-Woong ;
Journal of computational fluids engineering, volume 12, issue 4, 2007, Pages 20~27
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.
DEVELOPMENT OF A THREE-DIMENSIONAL MULTI-BLOCK STRUCTURED GRID DEFORMATION CODE FOR COMPLEX CONFIGURATIONS
Hoang, A.D. ; Lee, Y.M. ; Jung, S.K. ; Nguyen, A.T. ; Myong, R.S. ;
Journal of computational fluids engineering, volume 12, issue 4, 2007, Pages 28~37
In this study, a multi-block structured grid deformation code based on a hybrid of a transfinite interpolation algorithm and spring analogy was developed. The configuration was modeled by a Bezier surface. A combination of the spring analogy for block vertices and the transfinite interpolation for interior grid points helps to increase the robustness and makes it suitable for distributed computing. An elliptic smoothing operator was applied to the block faces with sub-faces in order to maintain the grid smoothness and skewness. The capability of this code was demonstrated on a range of simple and complex configurations including an airfoil and a wing-body configuration.
A COMPUTATIONAL STUDY ON THE CHARACTERISTICS OF FLOWFIELDS IN MICRONOZZLES
Seo, J.H. ; Cho, H.G. ; Lee, D.H. ; Jung, S.C. ; Myong, R.S. ; Huh, H.I. ;
Journal of computational fluids engineering, volume 12, issue 4, 2007, Pages 38~43
Owing to the rapid progress in manufacturing technology of microscale devices, there are active research works in developing microscale propulsion systems. In this study, gas flows in nozzles with size of milli and sub-millimeter are investigated by using a CFD code based on the Navier-Stokes equations. The prediction results were compared with theoretical results of quasi-one-dimensional nozzle flow and experiment data. In general, theoretical values agree very well with the CFD results. However, theoretical values begin to deviate from the CFD and experimental data for relatively small Reynolds numbers and the nozzle shape with rectangular cross section. The primary reason for this discrepancy is due to the existence of the thick boundary layer at the wall in low Reynolds flows.
HYDRODYNAMIC SOLVER FOR A TRANSIENT, TWO-FLUID, THREE-FIELD MODEL ON UNSTRUCTURED GRIDS
Jeong, J.J. ; Yoon, H.Y. ; Kim, J. ; Park, I.K. ; Cho, H.K. ;
Journal of computational fluids engineering, volume 12, issue 4, 2007, Pages 44~53
A three-dimensional (3D) unstructured hydrodynamic solver for transient two-phase flows has been developed for a 3D component of a nuclear system code and a component-scale analysis tool. A two-fluid three-field model is used for the two-phase flows. The three fields represent a continuous liquid, an entrained liquid, and a vapour field. An unstructured grid is adopted for realistic simulations of the flows in a complicated geometry. The semi-implicit ICE (Implicit Continuous-fluid Eulerian) numerical scheme has been applied to the unstructured non-staggered grid. This paper presents the numerical method and the preliminary results of the calculations. The results show that the modified numerical scheme is robust and predicts the phase change and the flow transitions due to boiling and flashing very well.
NUMERICAL INVESTIGATION OF THE FLOW IN A MICRONOZZLE FOR DISPENSING A HIGHLY VISCOUS SEALNT
Park, G.J. ; Kwak, H.S. ; Son, B.C. ; Kim, K. ;
Journal of computational fluids engineering, volume 12, issue 4, 2007, Pages 54~60
A theoretical and numerical investigation is performed on the flow in a micronozzle for precision-controlled sealant dispenser. The working fluid is a highly viscous epoxy used as sealant in producing LCD panels, which contains a number of tiny solid spacers. Flow analysis is conducted in order to achieve the optimal design of internal geometry of a nozzle. A simplified design analysis methodology is proposed for predicting the flow in the nozzle based on the assumption that the Reynolds number is much less than O(1). The parallel numerical computations are performed by using a CFD package FLUENT. Comparison discloses that the theoretical model gives a good prediction on the distribution of pressure and wall shear stress in the nozzle. However, the theoretical model has a difficulty in predicting the maximum wall shear stress as found in a limited region near edge by numerical computation. The theoretical and numerical simulations provide the good guideline for designing a dispensing micronozzle.
WAKE CHARACTERISTICS BEHIND TWO SPHERES IN A SIDE-BY-SIDE ARRANGEMENT
Kim, Dong-Joo ;
Journal of computational fluids engineering, volume 12, issue 4, 2007, Pages 61~67
Numerical simulation of laminar flow over two spheres in a side-by-side arrangement is carried out to investigate the effect of the inter-sphere spacing on the flow characteristics. The Reynolds numbers considered are 100, 250, and 300, covering the steady axisymmetric, steady planar-symmetric, and unsteady planar-symmetric flows in the case of a single sphere. Results show that the drag and lift coefficients and wake structures are significantly modified depending on both the Reynolds number and the spacing between the spheres. At Re=100, the flow is steady planar-symmetric irrespective of the spacing, but it shows some variation according to the spacing at Re=250 and 300. That is, the flow maintains planar symmetry of the single-sphere wake at large spacings, while it loses the symmetry at small spacings due to the generation of new asymmetric vortical structures. It is also shown that the drag and lift coefficients generally increase with decreasing inter-sphere spacing because the high pressure region is formed near the gap between the spheres.
AUTOMATIC GENERATION OF UNSTRUCTURED SURFACE GRID SYSTEM USING CAD SURFACE DATA
Lee, B.J. ; Kim, B.S. ;
Journal of computational fluids engineering, volume 12, issue 4, 2007, Pages 68~73
Computational Fluid Dynamics (CFD) approach is now playing an important role in the engineering process in these days. Generating proper grid system in time for the region of interest is prerequisite for the efficient numerical calculation of flow physics using CFD approach. Grid generation is, however, usually considered as a major obstacle for a routine and successful application of numerical approaches in the engineering process. CFD approach based on the unstructured grid system is gaining popularity due to its simplicity and efficiency for generating grid system compared to the structured grid approaches, especially for complex geometries. In this paper an automated triangular surface grid generation using CAD(Computer Aided Design) surface data is proposed. According to the present method, the CAD surface data imported in the STL(Stereo-lithography) format is processed to identify feature edges defining the topology and geometry of the surface shape first. When the feature edges are identified, node points along the edges are distributed. The initial fronts which connect those feature edge nodes are constructed and then they are advanced along the CAD surface data inward until the surface is fully covered by triangular surface grid cells using Advancing Front Method. It is found that this approach can be implemented in an automated way successfully saving man-hours and reducing human-errors in generating triangular surface grid system.
NUMERICAL STUDIES ON FLOWS WITH STRONG PROPERTY VARIATIONS THROUGH STRAIGHT RECTANGULAR CHANNELS
Choi, Nam-Jung ; Choi, Yun-Ho ;
Journal of computational fluids engineering, volume 12, issue 4, 2007, Pages 74~84
The flowfield characteristics in a straight rectangular channel have been investigated through a numerical model to analyze the regenerative cooling system that is used in rocket engine cooling. The supercritical hydrogen coolant introduces strong property variations that have a major influence on the developing flow and heat transfer characteristics. Of particular interest is the improved understanding of the physical characteristics of such flows through parametric studies. The approach used is a numerical solution of the full Navier-Stokes equations in the three dimensional form including the arbitrary equation of state and property variations. The present study compares constant and variable property solutions for both laminar and turbulent flow. For laminar flow, the variation of aspect ratio is examined, while for turbulent flow, the effects of variation of channel length and Reynolds number are discussed.
FLOW ANALYSIS AND PERFORMANCE EVALUATION OF HIGH PRESSURE DOUBLE STAGE RING BLOWER
Lee, K.D. ; Kim, K.Y. ;
Journal of computational fluids engineering, volume 12, issue 4, 2007, Pages 85~89
In the present work, flow analysis has been performed for side channel type double stage ring blower by solving three-dimensional Reynolds-averaged Navier-Stokes equation. Shear stress transport model is used as turbulent closure. The commercial CFD code CFX 11.0 is used for the calculations. Each of two stage is calculated separately and the second stage inlet flow is same as the first stage outlet flow so that consecutive calculation is possible. Velocity and pressure fields have been analyzed at the mid-plane between blades. The numerical results are validated with experimental data for head coefficients at different flow coefficients.