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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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NUMERICAL METHOD FOR VELOCITY PREDICTION CONSIDERING MOTION OF A YACHT
Park, M.Y. ; Lee, H. ; Park, S. ; Rhee, S.H. ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 1~7
DOI : 10.6112/kscfe.2014.19.3.001
One of the most important factors in sailing yacht design is an accurate velocity prediction. Velocity prediction programs (VPPs) are widely used to predict velocity of sailing yachts. VPPs, which are primarily based on experimental data and experience of long years, suffer limitations applied in realistic conditions. Thus, in the present study, a high fidelity velocity prediction method using the computational fluid dynamics (CFD) is proposed. Using the developed method, velocity and motion of a 30 feet sloop yacht, which was developed by Korea Research Institute of Ship and Ocean (KRISO) and termed KORDY30, were predicted in upwind sailing condition.
NUMERICAL ANALYSIS OF WAVE CHARACTERISTICS AROUND PERMEABLE SUBMERGED BREAKWATER ON THE POROUS SEABED
Kim, N.H. ; Woo, S.M. ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 8~13
DOI : 10.6112/kscfe.2014.19.3.008
In this study, wave characteristics coming with oblique incident angle to permeable trapezoidal submerged breakwater on the porous seabed are calculated by using boundary element method. This numerical analysis, based on the wave pressure function, is analyzing the continuity in the analytical region including fluid and structure. From the comparison of the reflection coefficients and damping coefficient, the results of this study are in good agreement with the existing results. The peak values of reflection coefficient obtained by permeable trapezoidal submerged breakwater on the porous seabed are smaller than those of permeable trapezoidal submerged breakwater on the non-porous seabed. The velocity vector in front of permeable trapezoidal submerged breakwater on the porous seabed is smaller than that in front of permeable trapezoidal submerged breakwater on the non-porous seabed with out the energy loss.
MODELING ON FLOW CHARACTERISTICS OF INERTANCE PULSE TUBE CRYOCOOLER
Han, S.H. ; Lee, K.H. ; Choi, J.W. ; Kim, J.S. ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 14~19
DOI : 10.6112/kscfe.2014.19.3.014
The flow characteristics of inertance pulse tube cryocooler(IPTC) was investigated with a computational thermal fluid dynamics for the reciprocating flow in IPTC including the piston movement of linear compressor. Two dimensional axisymmetric modeling was applied for the flow in an IPTC with a clearance between the piston and cylinder wall of linear compressor. The pressure, velocity, and temperature distribution were examined for the steady state. These were compared with previous results to confirm the validity in the modeling and computational results. The leakage between piston and cylinder wall affect the cooling capacity seriously. The dependence on mesh numbers were also examined to obtain a proper mesh numbers to improve the accuracy of calculation, which showed significant effect on the results. The user-defined function was used for the process of compression and expansion of piston.
NUMERICAL STUDY ON THE PERFORMANCE CHARACTERISTICS OF SHELL AND TUBE HEAT EXCHANGER BY FLOW DISTRIBUTORS : PART(I) FLOW CHARACTERISTICS
Park, Y.M. ; Chung, H.T. ; Kim, H.B. ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 20~23
DOI : 10.6112/kscfe.2014.19.3.020
The flow pattern inside the inlet chamber of the tube side is one of the key parameters influencing on the performances of the shell-and-tube type of heat exchangers(STHE). In order to improve the flow distribution, the baffle shaped as the porous plate is installed in the inlet chambers. In the present study, numerical simulation has been performed to investigate the flow features of the tube side of the STHE in sense of the hydraulic performances. The flow fields have been analysed by the three-dimensional Navier-Stokes solvers with the proper turbulent models. Computational domain is ranged in the whole of the tube side of the STHE. The numerical results showed that the presence of the baffles improves the redistribution of the flow injecting to the tube bundels. The good agreements of the numerical results with the experimental results of PIV measurements have been shown for the validation of the numerical methods adopted in the present papers.
THERMAL-FLUID ANALYSIS FOR COOLING PERFORMANCE IMPROVEMENT OF 3.3KV(105A) COMPACT RACK TYPE MEDIUM VOLTAGE INVERTER SYSTEM
Kim, S.Y. ; Kim, S.D. ; Ryoo, S.R. ; You, N.K. ; Kim, T.B. ; Hong, C.O. ; Ko, H.S. ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 24~28
DOI : 10.6112/kscfe.2014.19.3.024
With ever rising concerns about saving of fossil fuel resource, there have been an increasing demand for use of energy more efficiently. The electric motor driven inverters can be a great help to improve energy efficiency. They are also used to control the motor speed to the actual need. Therefore the use of them can lead to reduce energy consumption. In particular, the medium voltage(MV) drive systems used for pumps, fans, steel rolling mills and tractions have widespread applications in the industry. They cover power ratings from 0.4MW to 40MW at the MV level of 2.3kV to 13.8kV. The majority of the installed MV drive systems however, are in the 1MW to 4MW range with voltage rating from 3.3kV to 6.6kV. But they are required to reduce size and weight like other power electronic equipments. In this paper, we studied on the 3.3kV(105A) compact rack type inverter system for improving the cooling efficiency. At first, we confirmed the tendency of temperature with computational simulation using ANSYS ICEPAK and actual experimental tests. And then we researched thermal performance improvement designs in order to reduce temperature of the transformer for the safe operation. It can reduce temperature of transformer that using pipe type flow guide in the system. As a result, we found out more efficient solution by thermal-fluid analysis.
AERODYNAMIC DESIGN OPTIMIZATION OF UAV ROTOR BLADES USING A GENETIC ALGORITHM AND ARTIFICIAL NEURAL NETWORKS
Lee, H.M. ; Ryu, J.K. ; Ahn, S.J. ; Kwon, O.J. ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 29~36
DOI : 10.6112/kscfe.2014.19.3.029
In the present study, an aerodynamic design optimization of UAV rotor blades was conducted using a genetic algorithm(GA) coupled with computational fluid dynamics(CFD). To reduce computational cost in making databases, a function approximation was applied using artificial neural networks(ANN) based on a radial basis function network. Three dimensional Reynolds-Averaged Navier-Stokes(RANS) solver was used to solve the flow around UAV rotor blades. Design directions were specified to maximize thrust coefficient maintaining torque coefficient and minimize torque coefficient maintaining thrust coefficient. Design variables such as twist angle, thickness and chord length were adopted to perform a planform optimization. As a result of an optimization regarding to maximizing thrust coefficient, thrust coefficient was increased about 4.5% than base configuration. In case of an optimization minimizing torque coefficient, torque coefficient was decreased about 7.4% comparing with base configuration.
NUMERICAL STUDY OF NANOFLUIDS FORCED CONVECTION IN CIRCULAR TUBES
Choi, Hoon Ki ; Yoo, Geun Jong ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 37~43
DOI : 10.6112/kscfe.2014.19.3.037
In this paper, hydraulic & thermal developing and fully developed laminar forced convection flow of a water-
nanofluid in a circular horizontal tube with uniform heat flux at the wall, are investigated numerically. A single phase model employed with temperature independent properties. The thermal entrance length is presented in this paper. The variations of the convective heat transfer coefficient and shear stress are shown in the entrance region and fully developed region along different nanoparticles concentration and Reynolds numbers. Convective heat transfer coefficient for nanofluids is larger than that of the base fluid. It is shown that heat transfer is enhanced and shear stress is increased as the particle volume concentration increases. The heat transfer improves, as Reynolds number increases.
PARAMETRIC NUMERICAL STUDY OF THE REACTING FLOW FIELD OF A COAL SLURRY ENTRAINED GASIFIER
Song, W.Y. ; Kim, H.S. ; Shin, M.S. ; Jang, D.S. ; Lee, Jae-Goo ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 44~51
DOI : 10.6112/kscfe.2014.19.3.044
Considering the importance of the detailed resolution of the reacting flow field inside a gasifier, the objective of this study lies on to investigate the effect of important variables to influence on the reacting flow and thereby to clarify the physical feature occurring inside the gasifier using a comprehensive gasifier computer program. Thus, in this study the gasification process of a 1.0 ton/day gasifier are numerically modeled using the Fluent code. And parametric investigation has been made in terms of swirl intensity and aspect ratio of the gasifier. Doing this, special attention is given on the detailed change of the reacting flow field inside a gasifier especially with the change of this kind of design and operation parameters. Based on this study, a number of useful conclusions can be drawn in the view of flow pattern inside gasifier together with the consequence of the gasification process caused by the change of the flow pattern. Especially, swirl effect gives rise to a feature of a central delayed recirculation zone, which is different from the typical strong central recirculation appeared near the inlet nozzle. The delayed feature of central recirculation appearance could be explained by the increased axial momentum due to the substantial amount of the presence of the coal slurry occupying over the entire gasifier in gasification process. Further, the changes of flow pattern are explained in detail with the gasifier aspect ratio. In general, the results obtained are physically acceptable in parametric study.
EFFICIENT COMPUTATION OF COMPRESSIBLE FLOW BY HIGHER-ORDER METHOD ACCELERATED USING GPU
Chang, T.K. ; Park, J.S. ; Kim, C. ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 52~61
DOI : 10.6112/kscfe.2014.19.3.052
The present paper deals with the efficient computation of higher-order CFD methods for compressible flow using graphics processing units (GPU). The higher-order CFD methods, such as discontinuous Galerkin (DG) methods and correction procedure via reconstruction (CPR) methods, can realize arbitrary higher-order accuracy with compact stencil on unstructured mesh. However, they require much more computational costs compared to the widely used finite volume methods (FVM). Graphics processing unit, consisting of hundreds or thousands small cores, is apt to massive parallel computations of compressible flow based on the higher-order CFD methods and can reduce computational time greatly. Higher-order multi-dimensional limiting process (MLP) is applied for the robust control of numerical oscillations around shock discontinuity and implemented efficiently on GPU. The program is written and optimized in CUDA library offered from NVIDIA. The whole algorithms are implemented to guarantee accurate and efficient computations for parallel programming on shared-memory model of GPU. The extensive numerical experiments validates that the GPU successfully accelerates computing compressible flow using higher-order method.
AERODYNAMIC AND NOISE CALCULATIONS OF HELICOPTER ROTOR BLADES USING LOOSE CFD-CSD COUPLING METHODOLOGY
Kang, H.J. ; Kim, D.H. ; Wie, S.Y. ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 62~68
DOI : 10.6112/kscfe.2014.19.3.062
The aerodynamic and noise calculations were performed through the CFD-CSD loose coupling methodology. In the loose coupling process, the trimmed rotor airloads were predicted by the in-house CFD code based on unstructured overset meshes, and the trim of the rotorcraft and the aeroelastic deformation of rotor blades were accounted with the CAMRAD II rotorcraft comprehensive code. The set of codes was used to analyze the HART-II baseline test condition. The effect of grid resolution and time step was examined and the loose coupling approach was found to be stable and convergent for the case. Comparison of the resulting sectional airloads, structural deformations, the noise carpets and the wake geometry with experimentally measured data was presented and showed the good agreement.
NUMERICAL INVESTIGATION OF SHOCK-BUFFET ON TRANSPORT AIRCRAFT WITH CHANGING THE POSITION OF NACELLE/PYLON
Kim, S.H. ; Yee, K.J. ; Oh, S.J. ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 69~76
DOI : 10.6112/kscfe.2014.19.3.069
The shock buffet on a transonic transport aircraft are negative factors that reduce the aerodynamic performance of aircraft. The parametric studies were performed for position of nacelle/pylon to estimate the trend of flow mechanism under the wing that affects shock buffet. To generate external mesh of aircraft configuration that change the position of nacelle, snappyHexMesh provided in OpenFOAM was applied. Implicit density-based solver(ISAAC) was used for flow analysis. The change of nacelle position along horizontal direction dynamically affected the aerodynamic performance of transonic transport aircraft as comparing that of vertical direction. As a result of the parametric study of nacelle/pylon position, it was confirmed that the optimal position of nacelle can be obtained by aerodynamic design.
CURVED BOUNDARY TREATMENT OF THE LATTICE BOLTZMANN METHOD FOR SLIP FLOW SIMULATIONS
Jeong, Namgyun ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 77~84
DOI : 10.6112/kscfe.2014.19.3.077
The lattice Boltzmann (LB) method has been used to simulate rarefied gas flows in a micro-system as an alternative tool. However, previous results were mainly focused on a simple geometry with flat walls because the LB method is modeled on uniform Cartesian lattices. When previous boundary conditions for the microflows are applied to curved walls, the use of them requires approximation of the curved boundary by a series of stair steps, and introduces additional errors. For macroflows, no-slip curved wall boundary treatments have been developed remarkably in order to overcome these limits. However, the investigations for the slip curved wall boundary have rarely been performed for microflows. In this work, a curved boundary treatment of the LB method for a slip flow has been introduced. The results of the LB method for 2D microchannel and 3D microtube flows are in excellent agreement with the analytical solutions.
DEVELOPMENT OF A ROBUST MESHLESS METHOD FOR 2-D COMPRESSIBLE FLOW
Huh, J.Y. ; Rhee, J.S. ; Kim, K.H. ; Jung, S.Y. ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 85~90
DOI : 10.6112/kscfe.2014.19.3.085
The purpose of this study is to develop a new Meshless Method to solve 2-D compressible flow problems numerically. This paper includes a revised Least Square method that improves robustness compared with its original version by removing excessive numerical oscillation which occurs when points are randomly distributed. Numerical analyses of hypersonic flow over a blunt body were carried out using the method, then robustness, accuracy and convergence of their results were compared with those obtained from the original method.
GAS-LIQUID TWO-PHASE HOMOGENEOUS MODEL FOR CAVITATING FLOW -Part II. HIGH SPEED FLOW PHENOMENA IN GAS-LIQUID TWO-PHASE MEDIA
Shin, B.R. ; Park, S. ; Rhee, S.H. ;
Journal of computational fluids engineering, volume 19, issue 3, 2014, Pages 91~97
DOI : 10.6112/kscfe.2014.19.3.091
A high resolution numerical method aimed at solving cavitating flow was proposed and applied to gas-liquid two-phase shock tube problem with arbitrary void fraction. The present method with compressibility effects employs a finite-difference 4th-order Runge-Kutta method and Roe's flux difference splitting approximation with the MUSCL TVD scheme. The Jacobian matrix from the inviscid flux of constitute equation is diagonalized analytically and the speed of sound for the two-phase media is derived by eigenvalues. So that the present method is appropriate for the extension of high order upwind schemes based on the characteristic theory. By this method, a Riemann problem for Euler equations of one dimensional shock tube was computed. Numerical results of high speed flow phenomena such as detailed observations of shock and expansion wave propagations through the gas-liquid two-phase media and some data related to computational efficiency are made. Comparisons of predicted results and solutions at isothermal condition are provided and discussed.