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 17, Issue 4 - Dec 2012
Volume 17, Issue 3 - Sep 2012
Volume 17, Issue 2 - Jun 2012
Volume 17, Issue 1 - Mar 2012
Selecting the target year
SHAPE OPTIMIZATION OF THE AIRFOIL-GUIDE VANES IN THE TURNING REGION FOR A ROTATING TWO-PASS CHANNEL
Moon, M.A. ; Kim, K.Y. ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 1~10
DOI : 10.6112/kscfe.2012.17.2.001
This paper presents the numerical simulation results of heat transfer and friction loss for a rotating two-pass duct with the airfoil-guide vanes in the turning region. The Kriging model is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of flow field and heat transfer with shear stress transport turbulent model. To improve the heat transfer performance, angle and location of the airfoil-guide vanes have been selected as design variables. The optimization problem has been defined as a minimization of the objective function, which is defined as a linear combination of heat transfer related term and friction loss related term with a weight factor. The airfoil-guide vanes in the turning region keep the high level of heat transfer while the friction loss has a low value. By comparing the presence or absence of airfoil-guide vanes, it is shown that the airfoil-guide vanes exhibited the best heat transfer performance to improve the blade cooling except the first passage.
BENCHMARK TESTS FOR CFD CODES FOR THE ANALYSIS OF WIND FIELD IN THE FOREST
Park, T.W. ; Chang, S.M. ; Lee, B. ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 11~20
DOI : 10.6112/kscfe.2012.17.2.011
In this paper, the authors test various open codes and commercial codes based on CFD technology on the wind field around the complex terrain, which is a very important transport physics in the event of forrest fire. To study the physical mechanism inside the transition from surface fire to crown fire, the wake flow behind a parallel array of trees is studied numerically to show the flow separation in the turbulent boundary layer. Two sites near to Kunsan National University are chosen for the measurement of real wind field, and obtained data are compared with those from various computational codes such as Wind-Ninja, NIST-FDS, ANSYS-CFX, and ANSYS-FlUENT, etc. Through this research, feasibility and accuracy of the present CFD codes are investigated quantitatively, compared with the measured data with AWS.
CFD CODE DEVELOPMENT FOR THE PREDICTION OF THE SHIP RESISTANCE USING OPEN SOURCE LIBRARIES
Park, Sun-Ho ; Park, Se-Wan ; Rhee, Shin-Hyung ; Lee, Sang-Bong ; Choi, Jung-Eun ; Kang, Seon-Hyung ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 21~27
DOI : 10.6112/kscfe.2012.17.2.021
Reynolds-averaged Navier-Stokes equations solver based on a pressure-based cell-centered finite volume method was developed using OpenFOAM libraries, which was an open source and providing computational continuum mechanics libraries. For the reasonable development of the turbulent boundary layer on the bow of the ship, specified library was developed. Grid sensitivities, such as skewness and aspect ratio of a cell, were tested for the solution convergence. Pressure, turbulent kinetic energy, turbulent dissipation rate contours on the ship surface computed by the developed CFD code were compared with those computed by the commercial CFD code, Fluent.
RELIABILITY-BASED OPTIMIZATION OF AIRFOILS USING A MOMENT METHOD AND PARSEC FUNCTION
Lee, J. ; Kang, H. ; Kwon, J. ; Kwak, B. ; Jung, K. ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 28~34
DOI : 10.6112/kscfe.2012.17.2.028
In this study, the reliability-based design optimization of the airfoil was performed. PARSEC function was used to consider the uncertainty of the aerodynamic shape for the reliability-based shape optimization of airfoils. Among various reliability analysis methods, the moment method was used to compute the probability of failure of the aerodynamic performance. The accuracy of the reliability analysis was compared with other methods and it was found that the moment method predicts the probability of failure accurately. Deterministic and reliability-based optimizations were performed for the shape of the airfoil and it was demonstrated that reliability-based optimum assures the aerodynamic performances under uncertainties of the shape of the airfoil.
AN EFFICIENT INCOMPRESSIBLE FREE SURFACE FLOW SIMULATION USING GPU
Hong, H.E. ; Ahn, H.T. ; Myung, H.J. ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 35~41
DOI : 10.6112/kscfe.2012.17.2.035
This paper presents incompressible Navier-Stokes solution algorithm for 2D Free-surface flow problems on the Cartesian mesh, which was implemented to run on Graphics Processing Units(GPU). The INS solver utilizes the variable arrangement on the Cartesian mesh, Finite Volume discretization along Constrained Interpolation Profile-Conservative Semi-Lagrangian(CIP-CSL). Solution procedure of incompressible Navier-Stokes equations for free-surface flow takes considerable amount of computation time and memory space even in modern multi-core computing architecture based on Central Processing Units(CPUs). By the recent development of computer architecture technology, Graphics Processing Unit(GPU)'s scientific computing performance outperforms that of CPU's. This paper focus on the utilization of GPU's high performance computing capability, and presents an efficient solution algorithm for free surface flow simulation. The performance of the GPU implementations with double precision accuracy is compared to that of the CPU code using an representative free-surface flow problem, namely. dam-break problem.
THE EFFECTS OF WALL BOUNDARY CONDITIONS ON MASS TRANSFER IN TURBULENT PIPE FLOW
Kang, Chang-Woo ; Yang, Kyung-Soo ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 42~52
DOI : 10.6112/kscfe.2012.17.2.042
Direct Numerical Simulation(DNS) of turbulent mass transfer in fully developed turbulent pipe flow has been performed to study the effect of wall boundary conditions on the concentration fields at
=180 based on friction velocity and pipe radius. Fully developed turbulent pipe flows for Sc=0.71 are studied with two different wall boundary conditions, namely, constant mass flux and constant wall concentration. The mean concentration profiles and turbulent mass fluxes obtained from the present DNS are in good agreement with the previous numerical results currently available. To investigate the effects of wall boundary condition on the turbulent mass transfer, the mean concentration profile, root-mean-square of concentration fluctuation, turbulent mass fluxes and higher-order statistics(Skewness and Flatness factor) are compared for the two cases. Furthermore, the budgets of turbulent mass fluxes and concentration variance were computed and analyzed to elucidate the effects of wall boundary conditions on the turbulent mass transfer.
PERFORMANCE EVALUATION OF COOLING CHANNELS IN A PLASTIC INJECTION MOLD MODEL
Kim, H.S. ; Han, B.Y. ; Lee, I.C. ; Kim, Y.M. ; Park, H.K. ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 53~57
DOI : 10.6112/kscfe.2012.17.2.053
Design of the cooling channels of a plastic injection mold affects the quality and the productivity of the injection processes. In the injection process, the melted resin with high temperature enters the mold cavity, and just after the cavity is filled the heat should be dissipated through the cooling channels simultaneously. The purpose of this study is to analyse the heat transfer phenomenon and to estimate the temperature distribution in the mold to evaluate the cooling effect of the channels. The injection mold is assumed to have cooling channels of circular cross section and each channel has the same coolant flow rate. and The cavity has a rectangular shape. The results show that as the cooling channels get closer to the cavity surface, the cooling efficiency increases as might easily be guessed. However, due to the final hot resin flow from the gate an intensive cooling is required in that region.
NUMERICAL STUDY OF TURBULENT FLOW IN A INTAKE PART OF VACUUM CLEANER WITH ROLLING BRUSH
Park, Tae-Seon ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 58~64
DOI : 10.6112/kscfe.2012.17.2.058
Turbulent flows in a intake part of vacuum cleaner are studied by RANS simulations. The governing equations are solved by the SIMPLE algorithm based on the finite volume method of the unstructured grid system. The predicted results show that the suction performance is closely related to the variation of flow structure in the intake part. In order to investigate for the cleaning of bedclothes and carpet without sticking, several design changes are applied. The introduction of a solid cylinder in the intake part changes vortical structures significantly. Based on this result, a new design with spiral brushes is proposed. The design shows a good behavior for the suction performance and the flow control.
NUMERICAL STUDY OF THE EFFECTS OF THE GOVERNING NON-DIMENSIONAL PARAMETERS ON THE DROPLET EJECTION BEHAVIOR
Kim, E. ; Baek, J. ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 65~70
DOI : 10.6112/kscfe.2012.17.2.065
The droplet ejection behavior from drop-on-demand printhead are investigated numerically in terms of the non-dimensional parameters. The numerical simulation is performed using a volume-of-fluid model. It is important to eject droplet within the printability range, where the droplet is ejected in stable manner without satellite droplets. Generally, the printability range has been determined by Z number, which is the inverse of Oh number. However, it is found that the ejection of droplets with same Z number can exhibit different behavior depending on the value of Ca and We number. Therefore, it is insufficient to determine the printability range only with Z number. Instead, other non-dimensional parameters, such as Ca and We number, should be considered comprehensively.
CONTROL OF CIRCULAR CYLINDER WAKE USING PLASMA ACTUATION
Kim, Dong-Joo ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 71~77
DOI : 10.6112/kscfe.2012.17.2.071
Numerical simulations are carried out for flow over a circular cylinder controlled by the momentum forcing which is generated by a pair of plasma actuators symmetrically mounted on the cylinder surface. A popular and empirical plasma model is used for the spatial distribution of momentum forcing. In this study, we consider two different types of actuation, i.e., steady and unsteady (or pulsed) actuation. In the unsteady actuation, the actuation is turned on and off periodically, its frequency being a control parameter. The objective of this study is to investigate the effects of actuator location and actuation frequency on the flow structures and the forces on the cylinder. Results show that the cylinder wake can be effectively controlled by proper actuator location. For example, when the actuators are located at
from the stagnation point, vortex shedding is completely suppressed with the boundary layer almost fully attached to the surface, resulting in drag reduction and lift elimination.
A NUMERICAL INVESTIGATION OF THE EFFECT OF SURROUNDING BUILDINGS ON THE AERODYNAMIC PERFORMANCE OF A ROTOR SYSTEM ON THE WHIRL TOWER
Kang, Hee-Jung ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 78~84
DOI : 10.6112/kscfe.2012.17.2.078
Numerical calculations were performed to investigate the influence in aerodynamic characteristics of a rotor system by surrounding structures and the ground effect for the rotor blade on a whirl tower is also investigated. Three dimensional Navier-Stokes simulations were carried out by using unstructured overset mesh technique and parallel computation. The calculated hover performance showed good agreement with the experimental result and showed that the structures around the whirl tower did not affect the aerodynamic characteristics of the blade. The ground effect was studied by comparing with the numerical result for the out of ground condition and the result of an analytic model.
CONTROL OF SQUARE CYLINDER FLOW USING PLASMA SYNTHETIC JETS
Kim, Dong-Joo ; Kim, Kyoung-Jin ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 85~92
DOI : 10.6112/kscfe.2012.17.2.085
Flows over a square cylinder with and without plasma actuation are numerically investigated to see whether plasma actuation can effectively modify vortex shedding from the cylinder and reduce the drag and lift fluctuations. In this study, a plasma synthetic jet actuator is mounted on the rear side of cylinder as a means of direct-wake control. The effect of plasma actuation is considered by adding a momentum forcing term in the Navier-Stokes equations. Results show that the reduction of mean drag and lift fluctuations is obtained for both steady and unsteady actuation. However, the steady actuation is better than the unsteady one in terms of mean drag as well as drag fluctuations. With the strong steady actuation considered, the interaction of two separating shear layers from rear corners is effectively weakened due to the interference of synthetic jets. It results in a merging of synthetic-jet and shear-layer vortices and the increase of vortex shedding frequency. On the other hand, the unsteady actuation generates pulsating synthetic jets in the near wake, but it does not change the vortex shedding frequency for the actuation frequencies considered in this study.
COHERENT STRUCTURES IN DEVELOPING FLOW OVER A WAVY WALL
Chang, Kyoung-Sik ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 93~99
DOI : 10.6112/kscfe.2012.17.2.093
The present study focuses on the case of developing flow with in a channel containing a long array of sinusoidal waves (2a/
is the wavelength, 2a is the wave height, h is the mean channel depth) at the bottom wall. The Reynolds number defined with channel height, h and the mean velocity, U, is Re=6,700. The channel is sufficiently long such that transition is completed and the flow is fully developed over the downstream half of the channel. For the case of an incoming steady flow with no resolved turbulence, the instantaneous flow fields in the transition region are characterized by the formation of arrays of highly-organized large-scale hairpin vortices whose dimensions scale with that of the roughness elements. The paper explains the mechanism for the formation of these arrays of hairpin vortices and shows these eddies play the primary role in the formation of the large-scale streaks of high and low velocity over the wavy wall region. The presence of resolved turbulence in the incoming flow, reduces the streamwise distance needed for the streaks to develop over the wavy region, but does not affect qualitatively the transition process. In the fully-developed region, isolated and trains of large-scale hairpins play an important role in the dynamics of the streaks over the wavy wall.
COMPUTATIONAL PREDICTION OF ICE ACCRETION AROUND A ROTORCRAFT AIR INTAKE
Jung, K.Y. ; Ahn, G.B. ; Myong, R.S. ; Cho, T.H. ; Jung, S.K. ; Shin, H.B. ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 100~106
DOI : 10.6112/kscfe.2012.17.2.100
Ice accretion on the surface of aircraft in flight can adversely affect the safety of aircraft. In particular, it can cause degradation of critical aircraft performances such as maximum lift coefficient and total pressure recovery factor in engine air intake. In this study, computational prediction of ice accretion around a rotorcraft air intake is conducted in order to identify the impingement region with high droplet collection efficiency. Then the amount of ice accretion on the air intake, which is essential in determining the required power of ice protection system, is calculated. Finally, the effect of icing wind tunnel size is investigated in order to check the compatibility with the real in-flight test environment.
INERTIAL MIGRATION AND DYNAMICS OF AN ELASTIC CAPSULE IN CHANNEL FLOW
Shin, S.J. ; Sung, H.J. ;
Journal of computational fluids engineering, volume 17, issue 2, 2012, Pages 107~112
DOI : 10.6112/kscfe.2012.17.2.107
We explored the dynamic motions and the lateral equilibrium positions of an elastic capsule in channel flow at moderate Reynolds number varying Re, aspect ratio, size ratio, membrane stretching and bending coefficient. The transition of tank-treading/swinging to tumbling motion was observed in the simulations and the transition of dynamic motions for capsules resulted in different trend of the variation in the lateral equilibrium positions. Though other conditions were similar, the capsule with tumbling motion migrated closer to the wall than that with tank-treading motion.