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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 14, Issue 4 - Dec 2009
Volume 14, Issue 3 - Sep 2009
Volume 14, Issue 2 - Jun 2009
Volume 14, Issue 1 - Mar 2009
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A NUMERICAL STUDY ON THE COATING THICKNESS IN CONTINUOUS HOT-DIP GALVANIZING
Lee, Dong-Won ; Shin, Seung-Young ; Cho, Tae-Seok ; Kwon, Young-Doo ; Kwon, Soon-Bum ;
Journal of computational fluids engineering, volume 14, issue 1, 2009, Pages 1~8
To control the coating thickness of zinc in the process of continuous hot-dip galvanizing, it is known from early days that the gas wiping through an air knife system is the most effective because of the obtainable of uniformity of coating thickness, possibility of thin coating, working ability in high speed and simplicity of control. But, the gas wiping using in the galvanizing process brings about a problem of splashing from the strip edge for a certain high speed of coating. Also, it is known that the problem of splashing directly depends upon the galvanizing speed and nozzle stagnation pressure. In theses connections, in the present study, we proposed two kinds of air knife systems having the same expansion rate of nozzle, and the jet structures and coating thicknesses from a conventional and new proposed nozzles are compared. In numerical analysis, the governing equations consisted of two-dimensional time dependent Navier-Stokes equations, standard k-e turbulence model to solve turbulence stress and so on are employed. As a result, it is found that it had better to use the constant rate nozzle from the point view of the energy saving to obtain the same coating thickness. Also, to enhance the cutting ability at the strip, it is advisable to use an air knife with the constant expansion rate nozzle.
NUMERICAL STUDY ON THE COOLANT FLOW AND HEAT TRANSFER IN THE CYLINDER HEAD ASSEMBLY OF AN INTERNAL COMBUSTION ENGINE
Suh, Y.K. ; Heo, S.G. ; Kim, B.H. ;
Journal of computational fluids engineering, volume 14, issue 1, 2009, Pages 9~17
In this study we investigated the characteristics of fluid flow and heat transfer within a coolant passage in the cylinder head assembly of an internal combustion engine by using a commercial CFD code, CFX The complex coolant passage of the cylinder head assembly was modelled by suitable choice of a grid system and careful attention was paid in the construction of meshes near the walls where significant cooling occurs. To treat the simultaneous heating and cooling of the combustion walls we invented a methodology allowing a heat source within the solid wall and the convective cooling at the interface between the solid and the fluid. We managed to reproduce the experimental results by adjusting parameters appropriately. We have found that high temperature was concentrated at the surface of the cylinder jacket. It turned out that the effect of oil cooling from the piston head was unexpectedly significant. On the other hand the effect of cooling from the ambient air is almost negligible. The CFD method proposed in this study is believed to be useful in the early stage of the design of the engine-cooling system.
ADAPTIVE MOMENT-OF-FLUID METHOD : A NEW VOLUME-TRACKING METHOD FOR MULTIPHASE FLOW COMPUTATION
Ahn, Hyung-Taek ;
Journal of computational fluids engineering, volume 14, issue 1, 2009, Pages 18~23
A novel adaptive mesh refinement(AMR) strategy based on the Moment-of-Fluid(MOF) method for volume-tracking dynamic interface computation is presented. The Moment-of-Fluid method is a new interface reconstruction and volume advection method using volume fraction as well as material centroid. The adaptive mesh refinement is performed based on the error indicator, the deviation of the actual centroid obtained by interface reconstruction from the reference centroids given by moment advection process. Using the AMR-MOF method, the accuracy of volume-tracking computation with evolving interfaces is improved significantly compared to other published results.
MOLECULAR-DYNAMIC SIMULATION ON THE STATICAL AND DYNAMICAL PROPERTIES OF FLUIDS IN A NANO-CHANNEL
Hoang, Hai ; Kang, Sang-Mo ; Suh, Yong-Kweon ;
Journal of computational fluids engineering, volume 14, issue 1, 2009, Pages 24~34
The equilibrium molecular-dynamic simulations have been performed to estimate the properties of the three kinds of fluids confined between two plates that are separated by 1.086 nm; included in the statical properties are the density distribution and the static structure, and the autocorrelation velocity function in the dynamic property. Three kinds of fluids considered in this study are the Lennard-Jones fluid, water and aqueous sodium-chloride solution. The water molecules are modeled by using the SPC/E model and the ions by the charged Lennard-Jones particle model. To treat the water molecules, we combined the quaternion coordinates with Euler angles. We also proposed a plausible algorithm to assign the initial position and direction of molecules. The influence of polarization of water molecules as well as the presence of ions in the solution on the properties will be addressed in this study. In addition, we performed the non-equilibrium molecular-dynamic simulation to compute the flow velocity for the case with the gravitational force acting on molecules.
CONSERVATIVE FINITE VOLUME METHOD ON BOUNDARY TREATMENTS FOR FLOW NETWORK SYSTEM ANALYSES
Hong, S.W. ; Kim, C. ;
Journal of computational fluids engineering, volume 14, issue 1, 2009, Pages 35~44
To adequately analyze flows in pipe or duct network system, traditional node-based junction coupling methods require the junction loss which is specified by empirical or analytic correlations. In this paper, a new finite volume junction coupling method using a ghost junction cell is developed by considering the interchange of linear momentum as well as the important wall-effect at junction without requiring any correlation on the junction loss. Also, boundary treatment is modified to preserve the stagnation enthalpy across boundaries, such as pipe-end and the interface between junction and branch. Also, the computational accuracy and efficiency of the Godunov-type finite volume schemes are investigated by tracing the total mechanical energy of rapid transients due to sudden closure of valve at downstream end.
PREDICTION OF RIME ICE ACCRETION SHAPE ON 2D AIRFOIL
Back, S.W. ; Yee, K.J. ; Oh, S.J. ;
Journal of computational fluids engineering, volume 14, issue 1, 2009, Pages 45~52
Ice accretion may occur when the sold surface passes through the clouds containing supercooled water droplets. In the case of aircraft, it can result in serious performance degradation and safety hazard. In this study, numerical analysis code has been developed to predict the rime ice shapes on a 2-D airfoil and the computation results are validated against experimental data of NASA and other computation results of well-known ice prediction code, LEWICE. In addition, the effects of various numerical parameters on the ice shape have been systematically investigated.
BLADE PLANFORM OPTIMIZATION FOR HSI NOISE REDUCTION OF HELICOPTER
Chae, Sang-Hyun ; Yang, Choong-Mo ; Jung, Shin-Kyu ; Aoyama, Takashi ; Obayashi, Shigeru ; Yee, Kwang-Jung ;
Journal of computational fluids engineering, volume 14, issue 1, 2009, Pages 53~61
The objective of this research is to design blade planform to reduce high speed impulsive(HSI) noise from a non-lifting helicopter rotor using CFD method and optimization techniques. As for the aero-acoustic analysis, CFD technique for aerodynamic analysis and Kirchhoff's method for the acoustic analysis were used. As for the optimization method, Kriging-based genetic algorithm(GA) model as a high-fidelity optimization method was chosen. Design variables and constraints are determined for arbitrary blade planform. The result shows that the optimized blade planform with high swept-back and taper ratio can reduce HSI noise by suppressing generation of the strong shock wave on blade surface and propagation of the noise to the farfield flow region.
OPTIMAL DESIGN FOR COOLING SYSTEM OF DRIVING UNITS FOR HYBRID VEHICLES
Lee, K.H. ; Kim, Jae-Won ; Ahn, E.Y. ;
Journal of computational fluids engineering, volume 14, issue 1, 2009, Pages 62~69
The cooling system for electric devices of hybrid vehicles is examined. The present system is composed of coolant paths, inlet diffuser and heat sinks whose shapes are diamond and circular. In this work, inlet duct and fin arrays are combined in proposed models and examined by numerical calculations. Nusselt number and Reynolds number are considered for heat transfer performance. Main focus lies on the looking for optimal model for the cooling system adopted to compact driving module of a hybrid vehicle. The optimal model shows uniform flow patterns in the inlet diffuser and secondary flows after the fins attached to heat source. It is found that the vortical flows around the heat sinks are effective for heat removal mechanism.
A NUMERICAL STUDY ON JET IMPINGEMENT OF PULSED PLASMA DISCHARGE ON A FLAT PLATE
Kim, K. ; Kwak, H.S. ; Park, J.Y. ;
Journal of computational fluids engineering, volume 14, issue 1, 2009, Pages 70~77
In this study, time-dependent numerical analysis was carried out to investigate the plasma jet impingement on a flat plate, and a compressible form of two-dimensional inviscid gas dynamics equations were solved using the flux corrected transport algorithm. The mathematical modeling of Joule heating in the polycarbonate capillary bore and the mass ablation from the bore wall was incorporated in the numerical analysis and the series of computation was performed for three cases depending on the distance of the opposing plate from the capillary exit. The computational results reveal that the presence of the opposing plate does not affect the flow conditions inside the capillary when compared to the case of open-air plasma discharge. In the exterior region, the flow structure shows the typical supersonic underexpanded jet which consists of the strong Mach disk in front of the opposing plate and the barrel shock at the side of the jet. It is found that the shock evolution becomes more quasi-steady when the plate distance decreases. Also, the effects of the distance between the capillary bore exit and the opposing plate on the flow conditions along the opposing plate are investigated and the pressure variation on the plate shows more complicated interaction between the plasma discharge and the opposing plate when the location of plate becomes closer to the capillary exit.
A STUDY ON FLOW IN A SLIT NOZZLE FOR DISPENSING A LOW-VISCOSITY SOLUTION OF SINGLE-WALLED CARBON NANOTUBES
Shon, B.C ; Kwak, H.S. ; Lee, S.H. ;
Journal of computational fluids engineering, volume 14, issue 1, 2009, Pages 78~85
A combined theoretical and numerical study is conducted to design a slit nozzle for large-area liquid coating. The objectives are to guarantee the uniformity in the injected flow and to provide the capability of explicit control of flow rate. The woking fluid is a dilute aqueous solution containing single-walled carbon nanotubes and its low viscosity and the presence of dispersed materials pose technical hurdles. A theoretical analysis leads to a guideline for the geometric design of a slit nozzle. The CFD-based numerical experiment is employed as a verification tool. A new flow passage unit, connected to the nozzle chamber, is proposed to permit the control of flow rate by using the commodity pressurizer. The numerical results confirm the feasibility of this idea. The optimal geometry of internal structure of the nozzle has been searched for numerically and the related issues are discussed.
NUMERICAL ANALYSIS OF GAS FLOWS IN ULTRA-THIN FILM GAS BEARINGS USING A MODEL BOLTZMANN EQUATION
Chung, C.H. ;
Journal of computational fluids engineering, volume 14, issue 1, 2009, Pages 86~95
A kinetic theory analysis is used to study the ultra-thin gas flow field in gas bearings. The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. Calculations are made for flows inside micro-channels of backward-facing step, forward-facing step, and slider bearings. The results are compared well with those from the DSMC method. The present method does not suffer from statistical noise which is common in particle based methods and requires less computational effort.