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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 19, Issue 4 - Dec 2014
Volume 19, Issue 3 - Sep 2014
Volume 19, Issue 2 - Jun 2014
Volume 19, Issue 1 - Mar 2014
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STUDY ON VIEW FACTOR CALCULATION FOR RADIATIVE HEAT TRANSFER BY USING THE MESH SUBDIVISION METHOD
Kim, D.G. ; Han, K.I. ; Choi, J.H. ; Lee, J.J. ; Kim, T.K. ;
Journal of computational fluids engineering, volume 19, issue 1, 2014, Pages 1~6
DOI : 10.6112/kscfe.2014.19.1.001
Since experiments on the actual operational status are said to be very impractical because of their economic and repeatability problems, it is difficult to understand the thermal profiles of aerospace or military equipments. Thus, the CFD codes with considering the radiation heat transfer are used to compensate the defect. In case, analyzing the radiation exchanges between the object surfaces are very important. Because the temperature and the IR signal distributions of the object surface are significantly affected by the radiative heat transfer. To achieve accurate thermal radiation exchange between surfaces, it is important to calculate the radiation view factor precisely. Finer subdivision of meshes can be used to increase the accuracy of radiation view factor, but if the mesh is subdivided infinitely, the time required for calculation increases significantly and thus decreasing the efficiency. If the subdivision is not sufficient, assurance of accuracy is not guaranteed. In this paper, optimal mesh subdivision method using the solid angle has been successfully tested and found to be useful in increasing the efficiency of calculating the shape factors.
COMPUTATIONAL INVESTIGATION OF THE HIGH TEMPERATURE REACTING GAS EFFECTS ON RE-ENTRY VEHICLE FLOWFIELDS
Kang, E.J. ; Kim, J.Y. ; Park, J.H. ; Myong, R.S. ;
Journal of computational fluids engineering, volume 19, issue 1, 2014, Pages 7~14
DOI : 10.6112/kscfe.2014.19.1.007
Aerothermodynamic characteristics of re-entry vehicles in hypersonic speed regimes are investigated by applying CFD methods based on the Navier-Stokes-Fourier equations. A special emphasis is placed on the effects of high temperature chemically reacting gases on shock stand-off distance and thermal characteristics of the flowfields. A ten species model is used for describing the kinetic mechanism for high temperature air. In particular, the hypersonic flows around a cylinder are computed with and without chemically reacting effects. It is shown that, when the chemically reacting effects are taken into account, the shock stand-off distance and temperature are significantly reduced.
NUMERICAL DIFFUSION DECREASE OF FREE-SURFACE FLOW ANALYSIS USING SOURCE TERM IN VOLUME FRACTION TRANSPORT EQUATION
Park, Sunho ; Rhee, Shin Hyung ;
Journal of computational fluids engineering, volume 19, issue 1, 2014, Pages 15~20
DOI : 10.6112/kscfe.2014.19.1.015
Accurate simulation of free-surface wave flows around a ship is very important for better hull-form design. In this paper, a computational fluid dynamics (CFD) code, termed SNUFOAM, which is based on the open source libraries, OpenFOAM, was developed to predict the wave patterns around a ship. Additional anti-diffusion source term for minimizing a numerical diffusion, which was caused by convection differencing scheme, was considered in the volume-fraction transport equation. The influence of the anti-diffusion source term was tested by applying it to free-surface wave flow around the Wigley model ship. In results, the band width of the volume fraction contours between 0.1 to 0.9 at the hull surface was narrowed by considering the anti-diffusion term.
STUDY ON FLOW CHARACTERISTICS FOR PRECISION CONTROL BUTTERFLY VALVE
Park, Song Mook ; Choi, Hoon Ki ; Yoo, Geun Jong ;
Journal of computational fluids engineering, volume 19, issue 1, 2014, Pages 21~26
DOI : 10.6112/kscfe.2014.19.1.021
Butterfly valve is a valve that controls fluid flow depending on the size of the opening angle. In general, the size of the opening angle of the valve increases, the fluid flow has also increased sharply. However, sometimes, in a specific piping system, a particular operating condition is needed that the fluctuation of the fluid flow should not have large amount although the size of opening angle of the valve become larger. In butterfly value, the shape of a typical thin plate, it is impossible to control a minute fluid, but in thick plate type, it is possible. In this study, we got the fluid flow control characteristics and pressure drop through both a numerical method and an experimental method about thick plate type. The numerical result and experimental result of flow coefficient show a similar pattern. In addition, we could find that minute fluid flow control was possible in the area of small size of the opening angle.
A STUDY ON IMPLICIT METHOD FOR SOLVING INCOMPRESSIBLE FLOW WITH UNSTRUCTURED MESHES
Kim, M.G. ; Ahn, H.T. ;
Journal of computational fluids engineering, volume 19, issue 1, 2014, Pages 27~33
DOI : 10.6112/kscfe.2014.19.1.027
A new and efficient implicit scheme is proposed to obtain a steady-state solution in time integration and the comparison of characteristics with the approximation ways for the implicit method to solve the incompressible Navier-Stokes equations is provided. The conservative, finite-volume cell-vertex upwind scheme and artificial compressibility method using dual time stepping for time accuracy is applied in this paper. The numerical results obtained indicate that the direct application of Jacobian matrix to the Lower and upper sweeps of implicit LU-SGS leads to better performance as well as convergence regardless of CFL number and true time step than explicit scheme and approximation of Jacobian matrix. The flow simulation around box in uniform flow with unstructured meshes is demonstrated to check the validity of the current formulation.
A NUMERICAL STUDY ON THE CONJUGATE HEAT TRANSFER OF AN OIL COOLER WITH OFFSET STRIP FINS FOR VARIOUS-FLOW RATES
Park, S.W. ; Choi, H.G. ;
Journal of computational fluids engineering, volume 19, issue 1, 2014, Pages 34~40
DOI : 10.6112/kscfe.2014.19.1.034
Conjugate heat transfer of an automotive oil cooler with offset-strip fins was numerically investigated to predict the performance of the oil cooler for various flow-rates. The simulations were conducted by directly modeling offset-strip fins with unstructured meshes. The incompressible Navier-Stokes equations coupled with energy equation were used for the present simulations. Heat transfer characteristics of the oil cooler was compared well with experimental results and the errors were approximately within 5 percents. It was found that the performance of the oil cooler increased as the flow-rate increased up to the flow-rate of 12 L/min, but the performance seemed to be saturated beyond a critical flow-rate, which was estimated as 15 L/min. Furthermore, it was confirmed that compared to the performance without fins, that of the oil cooler with offset-strip fins was increased by about 75 percents.
A STUDY ON THE AERODYNAMIC DRAG REDUCTION OF HIGH-SPEED TRAIN USING BOGIE SIDE FAIRING
Moon, J.S. ; Kim, S.W. ; Kwon, H.B. ;
Journal of computational fluids engineering, volume 19, issue 1, 2014, Pages 41~46
DOI : 10.6112/kscfe.2014.19.1.041
The aerodynamic drag of high-speed train has been calculated and the effect of bogie side fairing on the aerodynamic drag has been investigated. Computational Fluid Dynamics (CFD) simulation based on steady-state 3 dimensional Navier-Stokes equation has been conducted employing FLUENT 12 and the aerodynamic model of HEMU-430x, the Korean next generation high-speed train under development has been built using GAMBIT 2.4.6. Three types of bogie side fairing configuration, the proto-type without fairing, half-covered fairing to avoid the interference with the bogie frame and full-covered fairing have been adopted to the train model to compare the drag reduction effects of the bogie side fairing configurations and the numerical results yields that the bogie side fairing can reduce the aerodynamic drag of the 6-car trainset up to 7.8%. The aerodynamic drag coefficient of each vehicle as well as the flow structures around the bogie system have also been examined to analyze the reason and mechanism of the drag reduction by bogie side fairing.
NUMERICAL STUDY FOR THE FULL-SCALE ANALYSIS OF PLATE-TYPE HEAT EXCHANGER USING ONE-DIMENSIONAL FLOW NETWORK MODEL and ε-NTU METHOD
Kim, Minsung ; Min, June Kee ; Ha, Man Yeong ;
Journal of computational fluids engineering, volume 19, issue 1, 2014, Pages 47~56
DOI : 10.6112/kscfe.2014.19.1.047
Since a typical plate heat exchanger is made up of a huge number of unitary cells, it may be impossible to predict the aero-thermal performance of the full scale heat exchanger through three-dimensional numerical simulation due to the enormous amount of computing resources and time required. In the present study, a simple flow-network model using the friction factor correlation and a thermal-network model based on the effectiveness-number of transfer units (
-NTU) method has been developed. The complicated flow pattern inside the cross-corrugated heat exchanger has been modeled into flow and thermal networks. Using this model, the heat transfer between neighboring streams can be considered, and the pressure drop and the heat transfer rate of full-scale heat exchanger matrix are calculated. In the calculation, the aero-thermal performance of each unitary cell of the heat exchanger matrix was evaluated using correlations of the Fanning friction factor f and the Nusselt number Nu, which were calculated by unitary-cell CFD model.
EFFECTS OF ROUNDING CORNERS ON THE FLOW PAST A SQUARE CYLINDER
Park, Doohyun ; Yang, Kyung-Soo ; Lee, Kyongjun ; Kang, Changwoo ;
Journal of computational fluids engineering, volume 19, issue 1, 2014, Pages 57~63
DOI : 10.6112/kscfe.2014.19.1.057
This study performed numerical analysis for the characteristics of flow-induced forces and the flow instability depending on the cross-sectional shape of the cylinder in laminar flow. To implement the cylinder cross-section, we adopted an Immersed Boundary Method with marker particles. We analyzed flow characteristics based on the radius of corner curvature. Main parameters are corner radius and Reynolds number (Re). With Re
ASSESSMENT OF MARS FOR DIRECT CONTACT CONDENSATION IN THE CORE MAKE-UP TANK
Park, Keun Tae ; Park, Ik Kyu ; Lee, Seung Wook ; Park, Hyun Sik ;
Journal of computational fluids engineering, volume 19, issue 1, 2014, Pages 64~72
DOI : 10.6112/kscfe.2014.19.1.064
This study aimed at assessing the analysis capability of thermal-hydraulic computer code, MARS for the behaviors of the core make-up tank (CMT). The sensitivity study on the nodalization to simulate the CMT was conducted, and the MARS calculations were compared with KAIST experimental data and RELAP5/MOD3.3 calculations. The 12-node model was fixed through a nodalization study to investigate the effect of the number of nodes in the CMT (2-, 4-, 8-, 12-, 16-node). The sensitivity studies on various parameters, such as water subcooling of the CMT, steam pressure, and natural circulation flow were done. MARS calculations were reasonable in the injection time and the effects of several parameters on the CMT behaviors even though the mesh-dependency should be properly treated for reactor applications.
EFFECT OF EXIT SHAPE ON TURBULENT OUTFLOWS IN A DISTRIBUTION MANIFOLD
Lee, Joon Woo ; Park, Tae Seon ;
Journal of computational fluids engineering, volume 19, issue 1, 2014, Pages 73~79
DOI : 10.6112/kscfe.2014.19.1.073
Three-dimensional turbulent flows of a distribution manifold are studied by a turbulence model. To investigate the geometrical effects of the manifold, the length and area of exit port are changed. From the results, flow structures related to the outflow uniformity are examined and the deparure angles are obtained. The exit configuration depending on the departure angle has advantages to the outflow uniformity. That is, the decreased exit area in the streamwise direction improves the uniformity of exit flow. For the uniform effusion, the change of exit port by departure angle is more effective them the change of exit area.
ANALYSIS ON THE DYNAMIC STALL OVER AN OSCILLATING AIRFOIL USING TRANSITION TRANSPORT EQUATIONS
Jeon, S.E. ; Sa, J.H. ; Park, S.H. ; Byun, Y.H. ;
Journal of computational fluids engineering, volume 19, issue 1, 2014, Pages 80~86
DOI : 10.6112/kscfe.2014.19.1.080
Numerical investigation on the dynamic stall over an oscillating airfoil is presented. A Reynolds-Averaged Navier-Stokes (RANS) equations are coupled with transition transport equations for the natural transition. Computational results considering the turbulent transition are compared with the fully turbulent computations and the experimental data. Results with transition prediction show closer correlation with the experimental data than those with the fully turbulent assumption, especially in the reattachment region.