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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 20, Issue 4 - Dec 2015
Volume 20, Issue 3 - Sep 2015
Volume 20, Issue 2 - Jun 2015
Volume 20, Issue 1 - Mar 2015
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SIMULATION OF RELATIVE MOTION OF FLOATING BODIES INCLUDING EFFECTS OF A FENDER AND A HAWSER
Shin, Sangmook ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 1~9
DOI : 10.6112/kscfe.2015.20.1.001
A developed code is applied to simulate relative motion of floating bodies in a side-by-side arrangement, including effects of a fender and a hawser. The developed code is based on the flux-difference splitting scheme for immiscible incompressible fluids and the hybrid Cartesian/immersed boundary method. To validate the developed code for free surface flows around deforming boundaries, the water wave generation is simulated, which is caused by bed movement. The computed wave profile and time histories of wave elevation are compared with other experimental and computational results. The effects of a fender and a hawser are modeled by asymmetric force acting on the floating bodies according to a relative displacement with the bounds, in which the fender and the hawser exert no force on the bodies. It has been observed that the floating body can be accelerated by a gap flow due to a phase difference caused by the free surface. Grid independency is established for the computed time history of the body velocity, based on three different size grids.
THREE-DIMENSIONAL FLOW COMPUTATION AND PERFORMANCE CHARACTERISTICS ANALYSIS OF PROPELLERS FOR WATER TREATMENT MIXER
Bae, Y.G. ; Kim, D.H. ; Hwang, S.T. ; Moon, Y.J. ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 10~15
DOI : 10.6112/kscfe.2015.20.1.010
In this study, the characteristics of water treatment mixer with various propeller profiles are numerically invesitgated. The computation was conducted by solving the incompressible Navier-Stokes equations on unstructured tetrahedral elements with k-
turbulence model. It was found that the spreading angle and swirl magnitude of the jet are important factors for the mixer efficiency, since they clearly characterize the propeller and the frontal surface area of the propeller but not so much affected by the skew angle if it exceeds 30 degrees. The case1 and case2 models are found to show the best propeller efficiency. The case2 with low blade angle, however, requires the lowest power input for the same discharge capacity as the case1.
NUMERICAL STUDY OF THE SLOSHING PHENOMENON IN THE 2-DIMENSIONAL RECTANGULAR TANK WITH VARIABLE FREQUENCY AT A LOW FILLING LEVEL
Jung, J.H. ; Lee, C.Y. ; Yoon, H.S. ; Kim, H.J. ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 16~25
DOI : 10.6112/kscfe.2015.20.1.016
The present study investigates the sloshing phenomena in a two-dimensional rectangular tank at a low filling level by using a level set method based on finite volume method. The code validations are performed by comparing between the present results and previous numerical and experimental results, which gives a good agreement. Various excitation frequencies and excitation amplitude of the 30% filling height tank have been considered in order to observe the dependence of the sloshing behavior on the excitation frequency and amplitude. Regardless of excitation amplitude, the maximum value of wall pressure occurs when the excitation frequency reaches the natural frequency. The time sequence of free surface and corresponding streamlines for excitation frequencies have been presented to analysis the variation of wall pressure according to time, which contributes to explain the double peaks in the time variation of wall pressure.
DEVELOPMENT OF PROBLEM-SPECIFIC GRID GENERATION PROGRAM FOR EDUCATIONAL PURPOSE
Ryu, G.M. ; Kim, Byoungsoo ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 26~31
DOI : 10.6112/kscfe.2015.20.1.026
A grid generation program for specific problems is introduced. The program allows users to easily generate grid system for specific geometry such as an airfoil, cylinder, wedge, flat plate, and nozzle. Generating grid system for those problems can be proceeded with minimum user inputs such as geometry-defining parameters and grid-defining parameters. By using this program learning stage for preprocessing of CFD application can be efficiently shorten and novice students can learn and acquire experience by trying out grid generation and CFD solution by themselves.
ANALYSIS OF TURBULENT BOUNDARY LAYER FLOWS USING A TIME MARCHING METHOD
Gong, H. ; Lee, S. ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 32~38
DOI : 10.6112/kscfe.2015.20.1.032
A 3-dimensional compressible turbulent boundary layer solver has been developed. A time marching method is used to integrate the turbulent boundary layer equations. While the direct integration of the boundary layer equations is performed for unseparated flow regions, the inverse integration is performed for separated flow regions. The program is verified for flows that have analytical solutions or other numerical results. The solver will be merged with an Euler solver for viscous-inviscid interaction.
THE CORRELATION OF PRESSURE DROP FOR SURFACE ROUGHNESS AND CURVATURE RADIUS IN A U-TUBE
Park, J.H. ; Chang, S.M. ; Lee, S.Y. ; Jang, G.W. ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 39~46
DOI : 10.6112/kscfe.2015.20.1.039
In this research, we studied the pressure drop affecting on the internal surface roughness and the curvature radius of a U-tube, which is used for the cooling system in PWR(Pressurized Water Reactor). Using ANSYS-FLUENT, a commercial code based on CFD(Computational Fluid Dynamics) technique, we compared a Moody chart with the Darcy friction factor changed by a range of various surface roughness and Reynolds numbers of a straight pipe model. We studied the effect giving variation about a range of various surface roughness and the curvature radius of the full scale U-tube model. The material of the heat transfer tube is Inconel 690 used in the steam generator. We compared the velocity distribution of selected 4 locations, and derived the correlation between the surface roughness and the pressure drop for the U-tube of each representative curvature radius using the linear regression method.
COMPARISON OF TURBULENCE MODELS ON ANALYSIS OF AIRCRAFT CONFIGURATIONS AT TRANSONIC SPEED
Huh, J. ; Lee, N. ; Lee, S. ; Kwak, E. ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 47~56
DOI : 10.6112/kscfe.2015.20.1.047
In this paper, we study the effect of various turbulence models by comparing the aerodynamic characteristics and the flow patterns computed for aircraft models. An in-house CFD solver, MSAPv, that solves the three dimensional RANS equations with the turbulence model equations is used. The turbulence models used in this study are the Spalart-Allmaras model, Menter`s
SST model, Coakley`s
model, and Huang and Coakley`s
model. DLR-F6 WB and WBNP configurations are selected for the study. We concentrate on the separated flow pattern variations with the turbulence models at the wing-body junction and the wing-pylon junction as well as drag polar curves.
A VOLUME OF FLUID METHOD FOR FREE SURFACE FLOWS AROUND SHIP HULLS
Park, I.R. ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 57~64
DOI : 10.6112/kscfe.2015.20.1.057
This paper describes a volume of fluid(VOF) method, mRHRIC for the simulation of free surface flows around ship hulls and provides its validation against benchmark test cases. The VOF method is developed on the basis of RHRIC method developed by Park et al. that uses high resolution differencing schemes to algebraically preserve both the sharpness of interface and the boundedness of volume fraction. A finite volume method is used to solve the governing equations, while the realizable
model is used for turbulence closure. The present numerical results of the resistance performance tests for DTMB5415 and KCS hull forms show a good agreement with available experimental data and those of other free surface methods.
NUMERICAL STUDY ON THE EFFECT OF THE SHAPE OF THE HEAT TRANSFER PLATE ON THE THERMAL PERFORMANCE OF THE RADIATOR
Kim, Y.J. ; Doo, J.H. ; Ha, M.Y. ; Son, S.W. ; Kim, J.K. ; Lee, S.H. ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 65~76
DOI : 10.6112/kscfe.2015.20.1.065
In this study, the natural convection phenomenon of the air side and the forced convection phenomenon of the oil side were simulated in the radiator through a 3-D numerical analysis, and the total heat released by the oil side into the radiator heating plate and then to the air side was evaluated. Also, a quantitative analysis was carried out on the effect of each thermal resistance on the overall heat transfer coefficient through a 1-D thermal circuit analysis on the heat transfer mechanisms of the radiators considered in this study. In addition, for the diverse shapes of the heating plates considered in this study, the pressure drops of the oil side were quantitatively compared and evaluated. The temperatures at the air side and the oil side outlets of the radiators with 8 different fin shapes considered in this study had almost similar values showing a difference of +/-3% and, accordingly, the total heat transfer also showed similar heat dissipation performance in all the models. As a result of the 1-D thermal circuit analysis, in all the models considered in this study, while the thermal resistance of the air side accounted for 92% to 96% of the total, that of the oil side was 5 to 7%, and that of the heating plate showed a very small value of 0.02%.
NUMERICAL STUDY ON SYNTHETIC-JET-BASED FLOW SUPPLYING DEVICE
Park, M. ; Lee, J. ; Kim, C. ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 77~83
DOI : 10.6112/kscfe.2015.20.1.077
Flow characteristics of synthetic jet based flow supplying devices have been computationally investigated for different device shapes. Jet momentum was produced by the volume change of a cavity by two piezoelectric-driven diaphragms. The devices have additional flow path compared with the original synthetic jet actuator, and these flow path changes the flow characteristics of synthetic jet actuator. Four non-dimensional parameters, which were functions of the shapes of the additional flow path, were considered as the most critical parameters in jet performance. Comparative studies were conducted to compare volume flow rate and jet velocity. Computed results were solved by 2-D incompressible Navier-Stokes solver with k-w SST turbulence model. Detailed computations revealed that the additional flow path diminishes suction strength of the synthetic jet actuator. In addition, the cross section area of the flow path has more influence over the jet performances than the length of the flow path. Based on the computational results, the synthetic jet based flow supplying devices could be improved by applying suitable shape of the flow path.
CFD ANALYSIS FOR THERMAL MIXING CHARACTERISTICS OF A FLOW MIXING HEADER ASSEMBLY OF SMART
Kim, Y.I. ; Bae, Y.M. ; Chung, Y.J. ; Kim, K.K. ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 84~91
DOI : 10.6112/kscfe.2015.20.1.084
SMART adopts, very unique facility, an FMHA to enhance the thermal and flow mixing capability in abnormal conditions of some steam generators or reactor coolant pumps. The FMHA is important for enhancing thermal mixing of the core inlet flow during a transient and even during accidents, and thus it is essential that the thermal mixing characteristics of flow of the FMHA be understood. Investigations for the mixing characteristics of the FMHA had been performed by using experimental and CFD methods in KAERI. In this study, the temperature distribution at the core inlet region is investigated for several abnormal conditions of steam generators using the commercial code, FLUENT 12. Simulations are carried out with two kinds of FMHA shapes, different mesh resolutions, turbulence models, and steam generator conditions. The CFD results show that the temperature deviation at the core inlet reduces greatly for all turbulence models and steam generator conditions tested here, and the effect of mesh refinement on the temperature distribution at the core inlet is negligible. Even though the uniformity of FMHA outlet hole flow increases the thermal mixing, the temperature deviation at the core inlet is within an acceptable range. We numerically confirmed that the FMHA applied in SMART has an excellent mixing capability and all simulation cases tested here satisfies the design requirement for FMHA thermal mixing capability.
ANALYSIS OF HEAT TRANSFER PERFORMANCE WITH ASPECT AND FILLING RATIOS IN THERMOSYPHON
Kim, Y.C. ; Choi, J.W. ; Kim, S.C. ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 92~98
DOI : 10.6112/kscfe.2015.20.1.092
Thermal-fluid analysis is performed numerically to figure out the characteristics of heat transfer in a thermosyphon varying with the aspect ratio of geometry and the filling ratio of working fluid. The computational results are reasonable compared with the experimental data and visualized. The thermal resistance and the convective heat transfer coefficients are evaluated with the aspect ratio of thermosyphon and the filling ratio of working fluid, respectively. In conclusion, the thermal resistance decreases as the length of evaporator increases. However, the variation of a condenser length is nearly independent on the thermal resistance. In order to raise the performance of thermosyphon, the working fluid needs to be filled over 75%. In addition, Nusselt numbers in the evaporator and the condenser show 275 and 304, respectively.
A COMPUTATIONAL STUDY OF ESTIMATING AERO-OPTIC BORESIGHT ERROR FOR A HYPERSONIC FLIGHT VEHICLE
Lim, Seol ; Chae, Hoon ; Kim, Jongju ;
Journal of computational fluids engineering, volume 20, issue 1, 2015, Pages 99~104
DOI : 10.6112/kscfe.2015.20.1.099
Aero-optic phenomena cause the image position displacement on an imaging plane of the airborne optical/IR systems. Particularly, the aero-optic boresight error(BSE) is important factor for homing, positioning and aiming applications of hypersonic flight interceptor missile. In this paper, an estimating method of aero-optic BSE for a hypersonic flight vehicle is studied. A ray tracing method and a transform method of refractive index fields from flow density fields are combined with computational fluid dynamics(CFD) method.