Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of computational fluids engineering
Journal Basic Information
Journal DOI :
Korea Society of Computational Fluids Engineering
Editor in Chief :
Volume & Issues
Volume 14, Issue 4 - Dec 2009
Volume 14, Issue 3 - Sep 2009
Volume 14, Issue 2 - Jun 2009
Volume 14, Issue 1 - Mar 2009
Selecting the target year
NUMERICAL OPTIMIZATION OF TEMPERATURE DISTRIBUTION IN HRSG SYSTEM USING INLET GUIDE VANE
Lee, Soo-Yoon ; Ahn, Joon ; Shin, Seung-Won ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 1~8
Diverging channel from gas engine exit to the inlet section of Heat Recovery Steam Generator (HRSG) has been re-designed for 1 MW system. To improve the uniformity in velocity and temperature distribution of existing design(Case A and B), two additional test geometries have been chosen for the numerical simulation. At first, gas burner exit section has been centered to the inlet section of the boiler(Case C) and uniformity in velocity and temperature distribution has been improved considerably. Secondly, the diverging channel length can be further reduced to compact geometry with new guide vane design (Case D and E). Proposed design shows overall improvement in uniformity in velocity and temperature distribution compared to existing one.
FLOW-INDUCED FORCES ON AN INCLINED SQUARE CYLINDER
Yoon, Dong-Hyeog ; Yang, Kyung-Soo ; Choi, Choon-Bum ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 9~15
Numerical investigation has been carried out for laminar flow past an inclined square cylinder in cross freestream. In particular, inclination of a square cylinder with respect to the main flow direction can cause sudden shift of the separation points to other edges, resulting in drastic change of flow-induced forces on the cylinder such as Strouhal number (St) of vortex shedding, drag and lift forces on the cylinder, depending upon the inclination angle. Collecting all the numerical results obtained, we propose contour diagrams of drag/lift coefficients and Strouhal number on an Re-Angle plane. This study would be the first step towards understanding flow-induced forces on cylindrical structures under a strong gust of wind from the viewpoint of wind hazards.
THE EFFECT OF RADIAL TEMPERATURE GRADIENT ON THE CIRCULAR-COUETTE FLOW
Kang, Chang-Woo ; Yang, Kyung-Soo ; Mutabazi, Innocent ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 16~24
Numerical simulation has been carried out to investigate the influence of radial temperature gradient on the Circular-Couette flow. Varying the Grashof number, we study the detailed flow and temperature fields. The current numerical results show good agreement with the analytical and experimental results currently available. It turns out that spiral vortices are generated by increasing temperature gradient. We classify the flow patterns for various Grashof number based on the characteristics of flow fields and spiral vortices. The correlation between Richardson number with wave number shows that the spiral angle and size of spiral vortices increase with increasing Richardson number.
THE STUDY OF AERO-ACOUSTICS CHARACTERISTICS BY THE BOUNDARY CONDITIONS OF HIGH ORDER SCHEME
Lee, S.S. ; Kim, J.S. ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 25~32
The present paper focuses on the analysis of aero-acoustics characteristic by appling different four boundary conditions. The high-order and high-resolution numerical schemes are used for discrete accurate computation of compressible flow. The four boundary conditions include extrapolation, characteristic boundary condition, zonal characteristic boundary condition. These boundary conditions are applied to the computation of two dimensional circular cylinder flows with Mach number of 0.3 and Reynolds number of 400. The computation results are validated against measurement data and other computation results for the Strouhal frequency of vortex shedding, the mean drag coefficient and root-mean-square lift for the unsteady periodic flow regime. The characteristics of secondary frequency is predicted by three kinds of boundary conditions.
NUMERICAL ANALYSIS OF UNSTEADY VISCOUS FLOWS USING A FAST GRID DEFORMATION TECHNIQUE ON HYBRID UNSTRUCTURED MESHES
Lee, H.D. ; Jung, M.S. ; Kwon, O.J. ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 33~48
In the present study, a fast grid deformation technique has been incorporated into the unsteady compressible and incompressible viscous flow solvers on unstructured hybrid meshes. An algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements, and a ball-vertex spring analogy was adopted for inviscid elements among several spring analogy methods due to its robustness. The present method was validated by comparing the results obtained from the grid deformation and the rigid motion of entire grids. Fish swimming motion of an NACA0012 airfoil and flapping wing motion of a generic fighter were also simulated to demonstrate the robustness of the present grid deformation technique.
NUMERICAL STUDY ON THE CHARACTERISTICS OF VORTEX FREQUENCY AND LAMINAR MIXING OF A PASSIVE SCALAR IN COAXIAL JET FLOWS
Kim, Won-Hyun ; Park, Tae-Seon ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 49~55
This study focuses on the near-field vortical structure and dynamics of coaxial jets. The characteristics of laminar flow and mixing in coaxial jets are investigated using a unsteady flow simulation. In order to analyze the geometric effects on the vortical structure, several cases of different configurations are selected for various values of the velocity ratio of inner jet to outer jet. From the result, it is confirmed that the flow mixing is promoted by the development of vortical structure and the interaction between inner jet and outer jet. This feature is strongly related to the vortex frequency in the shear-layers. The vortex frequency depends on the velocity ratio and the lip thickness of inner nozzle, but the outer pipe length has no effect on the frequency variation.
CFD ANALYSIS ON HEAT TRANSFER PERFORMANCE OF A REFRIGERATOR CONDENSER
Yoo, S.S. ; Hwang, D.Y. ; Lee, M.S. ; Han, B.Y. ; Park, H.K. ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 56~62
In this study, the heat transfer and flow field of a condenser used for a Kim-chi refrigerator is analysed with numerical method. Main objective is to present the basic data for designing a new condenser model with improvement of heat transfer performance. For CFD analysis, a commercial code, STAR CCM+ was used. The water was used for the inner working fluid and the air was used for the outer fluid. The condenser type used in this study is a flat plate fin-and-tube heat exchanger. As analysis parameters, the effect of condenser geometry and air velocity was investigated. For validation of the numerical calculations, the results were compared with the experimental ones. The heat transfer rates for both results were consistent with each other by maximum 5 % error. Based on this comparison, the numerical analysis was done with some modifications. As a result, it has been observed that there is a suitable fin pitch with which heat transfer performance of condenser is maximized.
A LIQUID DROPLET SIMULATION ON ZIG-ZAG MOTION
Jung, Rho-Taek ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 63~68
The motion of a rising liquid droplet is different that of a bubble motion. Treatment of liquid drops is more complex because internal motion must be considered. A 3D unstructured CFD code has been developed to solve incompressible N-S equation for the droplet simulation. This front-tracking consideration which the interface is tracked explicitly is very available to apply for not only exact interface topology but also the high schmidt number issue, such as
dissolution. This paper is forced on the zig-zag motion of the liquid droplet. The simulation shows that if the rising droplet is located at the corner of the zig-zag path, the velocity is low and shape of the droplet is more spherical shape, results in the less drag coefficient. Twin horse shoe vortexes behind the rising droplet are presented and the topology of the droplet is compared with an experimental result during one period of the path.
THE PERFORMANCE ANALYSIS OF A CIRCULATING WATER PUMP FOR A NUCLEAR POWER PLANT
Lee, M.S. ; Han, B.Y. ; Hwang, D.Y. ; Yoo, S.S. ; Park, H.K. ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 69~75
The objective of this study is to investigate the suitable design for a domestic Circulating water pump(CWP), which is used in cooling-water intakes for the unit 3 and 4 of Yeonggwang nuclear power plant. All the simulations are performed, using CFD method with a commercial code STAR-CCM+ version 3.02. After modeling a present design of the pump, the flow around the rotating blade was calculated by using quasi-static method and sliding mesh method with the almost same condition as an actual state. Based on fundamental simulations with various depth of sea water, the reference pressure for the boundary condition of the present study was decided. To verify the reliability of the calculation results, the suction flow rate of the data was compared with that of the experimental data. As a result of this comparison, it is confirmed that two results are fairly consistent. For the improvement of the suction flow rate, computational analysis was done by changing a flow channel and blade shapes. It is shown that the suction flow rate of the new pump was improved.
THE FUNDAMENTAL SHOCK-VORTEX INTERACTION PATTERNS THAT DEPEND ON THE VORTEX FLOW REGIMES
Chang, Keun-Shik ; Barik, Hrushikesh ; Chang, Se-Myong ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 76~85
The shock wave is deformed and the vortex is elongated simultaneously during the shock-vortex interaction. More precisely, the shock wave is deformed to a S-shape, consisting of a leading shock and a lagging shock by which the corresponding local vortex flows are accelerated and decelerated, respectively: the vortex flow swept by the leading shock is locally expanded and the one behind the lagging shock is locally compressed. As the leading shock escapes the vortex in the order of microseconds, the expanded flow region is quickly changed to a compression region due to the implosion effect. An induced shock is developed here and propagated against the vortex flow. This happens for a strong vortex because the tangential flow velocity of the vortex core is high enough to make the induced-shock wave speed supersonic relative to the vortex flow. For a weak shock, the vortex is basically subsonic and the induced shock wave is absent. For a vortex of intermediate strength, an induced shock wave is developed in the supersonic region but dissipated prematurely in the subsonic region. We have expounded these three shock-vortex interaction patterns that depend on the vortex flow regime using a third-order ENO method and numerical shadowgraphs.
AN ANALYSIS OF DISCRETIZATION EFFECT OF MOMENTUM CONVECTION TERM FOR MULTI-DIMENSIONAL TWO-PHASE FLOWS
Park, I.K. ; Cho, H.K. ; Yoon, H.Y. ; Jeong, J.J. ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 86~94
The non-conservative form of momentum equations is often used for some two-phase flow codes instead of a conservative form because of numerical convenience. Another non-conservative form, so called, a semi-conservative form can improve the numerical solution of these codes maintaining the numerical convenience. It is close to the conservative form but still maintains the feature of the non-conservative form. A semi-conservative form of the momentum equations and a non-conservative form of the momentum equations are implemented in CUPID code. The numerical results of the semi-conservative and the non-conservative forms are compared against analytical solutions and the solutions of the FLUENT code that uses the conservative form. The results clearly showed that the semi-conservative form of the momentum equations provides better solutions than the non-conservative form, especially for heterogeneous two-phase flows.
EFFECTS OF OSCILLATING FREQUENCY ON TAYLOR VORTICES
Kang, Chang-Woo ; Yang, Kyung-Soo ; Mutabazi, Innocent ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 95~105
We study time-periodic Taylor-Couette flow with the outer cylinder at rest and the inner one oscillating with a mean angular velocity. Varying the frequency of inner cylinder, we investigate the change of Taylor vortices at a given amplitude and a mean angular velocity. With a small frequency of modulation, we find that Taylor vortices appear and disappear periodically. With a higher frequency, Taylor vortices do not disappear, but the intensity of Taylor vortices modulates periodically. As the frequency increases, Taylor vortices modulate harmonically.
NUMERICAL SIMULATION OF THE FLOW CHARACTERISTICS INSIDE A U-TYPE TUBE
Koh, D.H. ; Kang, D.J. ; Song, D.J. ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 105~114
A numerical study of the flow characteristics inside a U-type circular tube is carried out in this paper. The numerical simulations carried out by using a Navier-Stokes code which is commercially available. Before detailed numerical simulations, validation of present numerical approach is made by comparing numerical solutions with experimental data. Numerical simulations are performed to study the effect of curvature on the flow characteristics inside a U-type tube. Numerical solutions show that a significant effect on the secondary flow structure in the cross section of the tube, especially in the curved section is shown when the curvature ratio, ratio of curvature to tube diameter, is smaller than about 3.5. As the curvature ratio decreases below 3.5, a counter rotating vortex is found below the primary vortex in the cross section of the tube. Another dramatic change of the flow structure is the formation of streamwise separation zone when the curvature ratio is decreased below 1.25.
THE EXAMINATION OF ACCURACY OF FIRE-DRIVEN FLOW SIMULATION IN TUNNEL EQUIPPED WITH VENTILATION
Jang, Yong-Jun ; Lee, Chang-Hyun ; Kim, Hag-Beom ; Jung, Woo-Sung ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 115~122
Numerical methods are applied to simulate the smoke behavior in a ventilated tunnel using large eddy simulation (LES) which is incorporated in FDS (Fire Dynamics Simulator) with proper combustion and radiation model. In this study, present numerical results are compared with data obtained from experiments on pool fires in a ventilated tunnel. The model tunnel is
. Two fire scenarios with different ventilation rates are considered with two different fire strengths. The present results are analyzed with those from LES without combustion and radiation model and from RANS (
) model as well. Temperature distributions caused by fire in tunnel are compared with each other. It is found that thermal stratification and smoke back-layer can be predicted by FDS and the temperature predictions by FDS show better results than LES without combustion and radiation model. The FDS solver, however, failed to predict correct flow pattern when the high ventilation rate is considered in tunnel because of the defects in the tunnel-inlet turbulence and the near-wall turbulence.
EFFECT OF ORIENTATION OF A MAGNETIC FIELD ON MOTION OF AN ELECTRICALLY CONDUCTING FLUID IN A CONFINED ENCLOSURE
Han, C.Y. ; Jun, H.Y. ; Park, E.S. ;
Journal of computational fluids engineering, volume 14, issue 3, 2009, Pages 123~130
Hydromagnetic flow in a confined enclosure under a uniform magnetic field is studied numerically. The thermally active side walls of the enclosure are kept at hot and cold temperatures specified, while the top and bottom walls are insulated. The coupled momentum and energy equations associating with the electromagnetic retarding force as well as the buoyancy force terms are solved by an iterative procedure using the SIMPLER algorithm based on control volume approach. The changes in the flow and thermal field based on the orientation of an external magnetic field, which varies from 0 to
radians, are investigated. Resulting heat transfer characteristics are examined too.