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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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EFFECTS OF FIN SPACING ON CONVECTIVE HEAT TRANSFER FOR A CIRCULAR CYLINDER WITH ANNULAR FINS
Park, Tae Seon ; Kim, Chang Ha ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 1~7
DOI : 10.6112/kscfe.2014.19.2.001
This study is to analyze the local convective heat transfer for a circular cylinder with annular fins. The relation between wall heat transfer and three-dimensional flow is investigated for different distances of annular fins. Depending on the fin spacing, the flow structure is strongly changed by the variation of horseshoe vortices. As the fin spacing increases, the heat transfer rate is maximized at a certain condition. This is clearly obtained as the Reynolds number increases, and it is closely related to the development of horseshoe vortices.
A COMPARATIVE STUDY ON PREDICTION CAPABILITY OF AIRFOIL FLOWS USING A TRANSITION TRANSPORT MODEL
Sa, J.H. ; Jeon, S.E. ; Park, S.H. ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 8~16
DOI : 10.6112/kscfe.2014.19.2.008
Two-dimensional prediction capability of several analysis codes, such as XFOIL, MSES, and KFLOW, is compared and analyzed based on computational results of airfoil flows. To this end the transition transport equations are coupled with the Navier-Stokes equations for the prediction of the natural transition and the separation-induced transition. Experimental data of aerodynamic coefficients are used for comparison with numerical results for the transitional flows. Numerical predictions using the transition transport model show a good agreement with experimental data. Discrepancies have been found in the prediction of the pressure drag are mainly caused by the difference in the far-field circulation correction methods.
CAVITATION FLOW ANALYSIS OF HYDROFOIL WITH CHANGE OF ANGLE OF ATTACK
Kang, T.J. ; Park, W.G. ; Jung, C.M. ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 17~23
DOI : 10.6112/kscfe.2014.19.2.017
Cavitation causes a great deal of noise, damage to components, vibrations, and a loss of efficiency in devices, such as propellers, pump impellers, nozzles, injectors, torpedoes, etc. Thus, the cavitating flow simulation is of practical importance for many engineering systems. In the present work, a two-phase flow solver based on the homogeneous mixture model has been developed. The solver employs an implicit preconditioning, dual time stepping algorithm in curvilinear coordinates. The flow characteristics around Clark-Y hydrofoil were calculated and then validated by comparing with the experimental data. The lift and drag coefficients with changes of angle of attack and cavitation number were obtained. The results show that cavity length and lift, drag coefficient increase with increasing angle of attack.
PERFORMANCE ANALYSIS OF THE PARALLEL CUPID CODE IN DISTRIBUTED MEMORY SYSTEM BASED ETHERNET AND INFINIBAND NETWORK
Jeon, B.J. ; Choi, H.G. ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 24~29
DOI : 10.6112/kscfe.2014.19.2.024
In this study, a parallel performance of CUPID-code has been investigated for both Ethernet and Infiniband network system to examine the effect of cache memory and network-speed. Bi-conjugate gradient solver of CUPID-code has been parallelised by using domain decomposition method and message passing interface (MPI). It is shown that the parallel performance of Ethernet-network system is worse than that of Infiniband-network system due to the slow network-speed and a small cache memory. It is also found that the parallel performance of each system deteriorates for a small problem due to the communication overhead, but the performance of Infiniband-network system is better than Ethernet-network system due to a much faster network-speed. For a large problem, the parallel performance depends less on network system.
STUDY ON THE BEHAVIOR OF NEEDLES AND SPRINGS FALLING FREELY IN A VISCOUS FLUID
Gowtham, B. ; Suh, Y.K. ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 30~39
DOI : 10.6112/kscfe.2014.19.2.030
We report in this paper the analysis of the motion of a needle and a spring in a viscous fluid under the influence of gravitational force. Lateral shift as well as vertical motion of a needle falling in a viscous fluid has been observed from a simple experiment. We also observed the combined rotation and translation of a falling spring. The trajectory and velocity of the falling needle and the spring were obtained by using an image processing technique. We also conducted numerical simulation for both problems. For the falling-needle problem, we employed a theory; but it turns out that significant correction is required for the solutions to match the numerical and experimental data. For the falling spring problem various theoretical formula were tested for their justification, but none of the existing theories can successfully predict the numerical and experimental results.
NUMERICAL STUDY OF WEDGE FLOW IN RAREFIED GAS FLOW REGIME USING A SLIP BOUNDARY CONDITION
Choi, Y.J. ; Kwon, O.J. ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 40~48
DOI : 10.6112/kscfe.2014.19.2.040
For rarefied gas flow regimes, physical phenomena such as velocity slip and temperature jump occur on the solid body surface. To predict these phenomena accurately, either the Navier-Stokes solver with a slip boundary condition or the direct simulation Monte Carlo method should be used. In the present study, flow simulations of a wedge were conducted in Mach-10 flow of argon gas for several different flow regimes using a two-dimensional Navier-Stokes solver with the Maxwell slip boundary condition. The results of the simulations were compared with those of the direct simulation Monte Carlo method to assess the present method. It was found that the values of the velocity slip and the temperature jump predicted increase as the Knudsen number increases. Also, the results are comparatively reasonable up to the Knudsen number of 0.05.
DEVELOPMENT OF A 2-D GAS-KINETIC BGK SOLVER FOR CONTINUUM AND TRANSITIONAL FLOWS ON UNSTRUCTURED MESHES
Yang, T.H. ; Kwon, O.J. ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 49~57
DOI : 10.6112/kscfe.2014.19.2.049
In the present study, 2-D gas-kinetic flow solver on unstructured meshes was developed for flows from continuum to transitional regimes. The gas-kinetic BGK scheme is based on numerical solutions of the BGK simplification of the Boltzmann transport equation. In the initial reconstruction, the unstructured version of the linear interpolation is applied to compute left and right states along a cell interface. In the gas evolution step, the numerical fluxes are computed from the evaluation of the time-dependent gas distribution function around a cell interface. Two-dimensional compressible flow calculations were performed to verify the accuracy and robustness of the current gas-kinetic approach. Gas-kinetic BGK scheme was successfully applied to two-dimensional steady and unsteady flow simulations with strong contact discontinuities. Exemplary hypersonic viscous simulations have been conducted to analyze the performances of the gas-kinetic scheme. The computed results show fair agreement with other standard particle-based approaches for both continuum part and transitional part.
IMPLEMENTATION OF ADAPTIVE WAVELET METHOD FOR ENHANCEMENT OF COMPUTATIONAL EFFICIENCY FOR THREE DIMENSIONAL EULER EQUATION
Jo, D.U. ; Park, K.H. ; Kang, H.M. ; Lee, D.H. ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 58~65
DOI : 10.6112/kscfe.2014.19.2.058
The adaptive wavelet method is studied for the enhancement of computational efficiency of three-dimensional flows. For implementation of the method for three-dimensional Euler equation, wavelet decomposition process is introduced based on the previous two-dimensional adaptive wavelet method. The order of numerical accuracy of an original solver is preserved by applying modified thresholding value. In order to assess the efficiency of the proposed algorithm, the method is applied to the computation of flow field around ONERA-M6 wing in transonic regime with 4th and 6th order interpolating polynomial respectively. Through the application, it is confirmed that the three-dimensional adaptive wavelet method can reduce the computational time while conserving the numerical accuracy of an original solver.
A NUMERICAL STUDY ON THE EFFECT OF VEHICLE-TO-VEHICLE DISTANCE ON THE AERODYNAMIC CHARACTERISTICS OF A MOVING VEHICLE
Kim, D.G. ; Kim, C.H. ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 66~71
DOI : 10.6112/kscfe.2014.19.2.066
Aerodynamic design of a vehicle has very important meaning on the fuel economy, dynamic stability and the noise & vibration of a moving vehicle. In this study, the correlation of aerodynamic effect between two model vehicles moving inline on a road was studied with the basic SAE model vehicle. Drag and lift are two main physical forces acting on the vehicle and both of them directly effect on the fuel economy and driving stability of the vehicle. For the research, the distance between two vehicles is varied from 5m to 30m at the fixed vehicle speed, 100km/h and the side-wind was assumed to be zero. The main issue for this numerical research is on the understanding of the interaction forces; lift and drag between two vehicles formed inline. From the study, it was found that as the distance between two vehicles is closer, the drag force acting on both the front and rear vehicle decreases and the lift force has same trend for both vehicle. As the distance(D) is 5m, the drag of the front vehicle reduced 7.4% but 28.5% for the rear-side vehicle. As the distance is 30m, the drag of the rear vehicle is still reduced to 22% compared to the single driving.
A MULTI-DOMAIN APPROACH FOR A HYBRID PARTICLE-MESH METHOD
Lee, Seung-Jae ; Suh, Jung-Chun ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 72~78
DOI : 10.6112/kscfe.2014.19.2.072
A hybrid particle-mesh method as the combination between the Vortex-In-Cell (VIC) method and penalization method has been achieved in recent years. The VIC method, which is based on the vorticity-velocity formulation, offers particle-mesh algorithms to numerically simulate flows past a solid body. The penalization method is used to enforce boundary conditions at a body surface with a decoupling between body boundaries and computational grids. The main advantage of the hybrid particle-mesh method is an efficient implementation for solid boundaries of arbitrary complexity on Cartesian grids. However, a numerical simulation of flows in large domains is still not too easy. In this study, a multi-domain approach is thus proposed to further reduce computation cost and easily implement it. We validate the implementation by numerical simulations of an incompressible viscous flow around an impulsively started circular cylinder.
SIMULATION OF FREE SURFACE FLOW OVER TRAPEZOIDAL OBSTACLE WITH LATTICE BOLTZMANN METHOD
Korkmaz, Emrah ; Jung, Rho-Taek ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 79~85
DOI : 10.6112/kscfe.2014.19.2.079
An air-water free surface flow simulation by using the Lattice Boltzmann Method(LBM) has not been studied a lot compared with the done by the Navier-Stoke equation. This paper shows the LBM is as one of the application tools for the free surface movement over an obstacle. The Mezo scaled application tool has been developed with two dimensional and nine discretized velocity direction using conventional lattice Bhatnagar-Gross-Krook model. Boundary conditions of a halfway-based for solid wall and a kinematic-based for interface are adopted. A validation case with a trapezoidal shape bump to make a comparison between freesurface movements from computational results and experimental ones was described with grid size dependency.
PREDICTION OF SEPARATION TRAJECTORY FOR TSTO LAUNCH VEHICLE USING DATABASE BASED ON STEADY STATE ANALYSIS
Jo, J.H. ; Ahn, S.J. ; Kwon, O.J. ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 86~92
DOI : 10.6112/kscfe.2014.19.2.086
In this paper, prediction of separation trajectory for Two-stage-To-Orbit space launch vehicle has been numerically simulated by using an aerodynamic database based on steady state analysis. Aerodynamic database were obtained for matrix of longitudinal and vertical positions. The steady flow simulations around the launch vehicle have been made by using a 3-D RANS flow solver based on unstructured meshes. For this purpose, a vertex-centered finite-volume method was adopted to discretize inviscid and viscous fluxes. Roe`s finite difference splitting was utilized to discretize the inviscid fluxes, and the viscous fluxes were computed based on central differencing. To validate this flow solver, calculations were made for the wind-tunnel experiment model of the LGBB TSTO vehicle configuration on steady state conditions. Aerodynamic database was constructed by using flow simulations based on test matrix from the wind-tunnel experiment. ANN(Artificial Neural Network) was applied to construct interpolation function among aerodynamic variables. Separation trajectory for TSTO launch vehicle was predicted from 6-DOF equation of motion based on the interpolated function. The result of present separation trajectory calculation was compared with the trajectory using experimental database. The predicted results for the separation trajectory shows fair agreement with reference solution.
AERODYNAMIC DESIGN AND PERFORMANCE PREDICTION OF ROTOR BLADES IN A SINGLE-STAGE AXIAL FAN USING CFD METHODS
Kim, E.S. ; Chung, H.T. ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 93~98
DOI : 10.6112/kscfe.2014.19.2.093
In the present study, CFD methods are applied in the design procedure of rotor blades in a axial-flow fan and the aerodynamic performances are predicted. The blade profiles initially determined by the free vortex method and empirical formula are modified to match the target value of the rotor work load through the analysis of 3D Navier-Stokes solver. The corrected shapes of the rotor blade showed the increase of the efficiency and the pressure simultaneously.
A STUDY ABOUT FISH LOCOMOTION USING COMPUTATIONAL FLUID DYNAMICS
Kim, S.H. ; Jung, Y.S. ; Kwon, O.J. ;
Journal of computational fluids engineering, volume 19, issue 2, 2014, Pages 99~107
DOI : 10.6112/kscfe.2014.19.2.099
The aim of the present study is to investigate the flow interference between two adjacent undulating fish-like body, and its effect on the undulating propulsion. For this purpose, unsteady two dimensional incompressible flow calculations were conducted using an unstructured mesh flow solver, coupled with an overset mesh technique. To deal with mesh deformation due to fish locomotion, spring analogy is utilized. The fish body used in the simulation is constructed from the NACA0012 airfoil. The study indicates that the propulsion of undulating fish is proportional to frequency and wavelength of the midline oscillation when there is no adjacent fish. It also reveals that average thrust was increased when the vortex shedding from the tail was conserved well and pressure difference between upper and lower sides of the fish was magnified due to flow interference. From this study, which relative position and phase difference of locomotion between two fishes can generate maximum thrust was known among six different cases.