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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 9, Issue 4 - Dec 2004
Volume 9, Issue 3 - Sep 2004
Volume 9, Issue 2 - Jun 2004
Volume 9, Issue 1 - Mar 2004
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An Anomalous Bifurcation in Natural Convection between Two Horizontal Plates with Periodic Temperatures
Yoo Joo-Sik ; Kim Yong-Jin ;
Journal of computational fluids engineering, volume 9, issue 4, 2004, Pages 1~6
This study investigates the transition of flows in a natural convection problem with periodic wall temperatures of the form, T/sub L/=T₁＋δ Tsinκχ and T/sub L/=T₂＋δ Tsinκχ .The fluid considered is air with P/sub γ/=0.7. In the conduction-dominated regime with a small Rayleigh number, two large cells are formed over one wave length, for all wave numbers. When k≤1.8, the flow becomes unstable with increase of the Rayleigh number, and multicellular convection occurs above a critical Rayleigh number. The flow patterns are classified by the number of eddies over one wave length, and several kinds of transition phenomena, such as 2→3→4, 4→3→2, and 2→4 eddy flow, occur with increase( or decrease) of the Rayleigh number. Dual solutions are found above a critical Rayleigh number, and an anomalous bifurcation is observed.
The development of a mesh generation program using contour line data
Chin S. M. ; Won C. S. ; Hur N. ;
Journal of computational fluids engineering, volume 9, issue 4, 2004, Pages 7~12
In the present study a semi-automatic mesh generation program has been developed by using DXF file containing contour line data. The program consists of DXF file reader and mapping algorithm. Pre-generated 2-D planar mesh points are to be mapped one by one onto triangular surface whose three vertices are three nearest contour points surrounding the mapping point. The present program has been successfully tested for mesh generations for the road tunnel ventilation analysis and analysis of lava movement in mountain area.
Study of Flow Analysis of a Mid-size Vehicle in an Engine Room
Lee Dong-Ryul ;
Journal of computational fluids engineering, volume 9, issue 4, 2004, Pages 13~19
Flow distribution of a mid-size vehicle in engine room was investigated numerically to analyze the flow performance of given design cases in a front body of the mid-size vehicle. The data analyzed are the mass flow rate at the upper and lower openings, in the radiator, and the degree of non-uniformity of the velocity field at the inlet of the radiator. It is presented that the shape of the front end and the presence of the undercover greatly affect the flow fields, therefore, the flow performance.
Quantification of the Mixing Effect by Using the Method of Material-Stretching Mapping
Suh Y. K. ;
Journal of computational fluids engineering, volume 9, issue 4, 2004, Pages 20~33
In this study a stretching-mapping method is proposed for calculating the materials' stretching exponents, which are to be used in quantification of the mixing effect. In this method, the mapping tensor associated with the deformation of each fluid material is first obtained. Then deformations of a lot of materials are obtained by applying the mapping tensor. The local stretching rates and their space-average values are next computed with the mapped deformations. Application to a simple time-periodic flow within a cavity shows that the method is indeed effective compared with the conventional method; i.e. the mapping method is fast and yields the same results as the conventional one.
Influence of the Anastomosis Angle Variation on Flow Features and Wall Shear Stress of an Artery
Kim H. M. ;
Journal of computational fluids engineering, volume 9, issue 4, 2004, Pages 34~40
It is known that the non-planar model of bypass is more profitable to suppress the development of intimal hyperplasia that tends to occur preferentially in regions of low time averaged shear stress and rapid temporal changes in wall shear stress. In this study it was numerically simulated the blood flow in an coronary artery grafted by artificial bypass to determine the flow characteristic variations due to the anastomosis angle changing. 5 different non-planar anastomosis angle models such as 45°, 60°, 90°, 120° and 135° were considered. When the anastomosis angle is higher, the backward flow region is spatially extended near the downstream region of the anastomosis because of the development of horseshoes vortex. For the case of the nan-planar 45° and 60° of anastomosis, the area of low-OSI zone was decreased by 26% and 13% respectively and the time averaged wall shear stress was increased by more than 55% as compared with 45° of planar model. However, both of the area of the low-OSI zone and the time averaged wall shear stress of 90°, 120° model were significantly increased.
Unsteady 2-D Laminar Flow Simulation past a Circular Cylinder
Myong Hyon Kook ;
Journal of computational fluids engineering, volume 9, issue 4, 2004, Pages 41~47
The paper presents numerical simulations of laminar vortex-shedding flows past a circular cylinder for Re ≤ 500. The simulations are performed by solving the unsteady 2-D Navier-Stokes equations with a finite volume method using unstructured grid system. The resulting Reynolds number dependence of the Strouhal number and of the drag and lift coefficients is compared with experiments and with previous numerical results, showing good agreement. It is found that, for the truly laminar Reynolds number range the present calculation method described is capable of producing reasonably accurate results for the main practically relevant parameters such as Strouhal number, drag and lift coefficients.
Flow Simulation past a Circular Cylinder by 2-D URANS
Myong Hyon Kook ;
Journal of computational fluids engineering, volume 9, issue 4, 2004, Pages 48~54
Vortex-shedding flows past a circular cylinder for 200≤ Re ≤ 5000 are numerically simulated with the PowerCFD code, using a finite volume method and an unstructured grid system, developed by the author. The simulation is peformed by solving the unsteady 2-D Wavier-Stokes equations with both no model and turbulence model. The resulting Reynolds number dependence of the Strouhal number and of the drag and lift coefficients is compared with both experiments and previous numerical results. It is found that, in the range of 200≤ Re ≤ 5000 the calculation method with a turbulence model is capable of producing reasonably more accurate results than that with no model for the main practically relevant parameters such as Strouhal number, drag and lift coefficients.
Analysis of the Stokes Flow and Stirring Characteristics in a Staggered Screw Channel
Suh Y. K. ;
Journal of computational fluids engineering, volume 9, issue 4, 2004, Pages 55~63
The three-dimensional Stokes flow within a staggered screw channel is obtained by using a finite volume method. The geometry is intended to mimic the single screw extruder having staggered arrangement of flights. The flow solution is then subjected to the analysis of the stirring performance. In the analysis of the stirring performance, the stretching-mapping method developed by the author is employed for calculating the materials' stretching exponents, which are to be used in quantification of the mixing effect. The numerical results Indicate that the staggered geometry gives indeed far much better stirring-performance than the standard (nonstaggered) flight geometry. It was also shown that care must be given to the selection of the basis planes for evaluating the local stretching rate, and it turns out that the best method (H-method) has its basis plane just on the half way between the past and future evolution of fluid particles subjected to the defromation. In evaluating the stretching exponent, the expansion ratio must be considered which is one of the characteristic differences of the actual three-dimensional flows from the two-dimensionmal counterparts. The larger axial pressure-difference causes in general the smaller stirring performance while the flow rate is increased. The smaller channel length also increases the stirring performance.
Numerical Analysis of Ultra-Thin Gas Film Lubrication
Chung C. H. ;
Journal of computational fluids engineering, volume 9, issue 4, 2004, Pages 64~70
A kinetic theory analysis is used to study the ultra-thin gas flow field in a gas slider bearing. The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. Calculations are made for a flow in a micro-channel between an inclined slider and a moving disk drive platter The results are compared well with those from the DSMC method. The present method does not suffer from statistical noise which is common in particle-based methods and requires much less computational effort.
KAIST 항공우주공학전공 전산공기역학 및 최적설계 연구실 소개
Journal of computational fluids engineering, volume 9, issue 4, 2004, Pages 71~75