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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 15, Issue 4 - Dec 2010
Volume 15, Issue 3 - Sep 2010
Volume 15, Issue 2 - Jun 2010
Volume 15, Issue 1 - Mar 2010
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CONVECTIVE HEAT TRANSFER CHARACTERISTICS OF OVAL FIN-CIRCULAR TUBE HEAT EXCHANGER
Kang, H.C. ; Lee, J.H. ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 1~6
The purpose of the present study is to investigate the flow resistance and the heat transfer characteristics of oval fin-tube heat exchanger. Six kinds of oval fin having the same fin area and different diameter ratio tested numerically. Test data for the heat transfer, pressure drop and fin temperature were shown and discussed. The pressure drop and heat transfer increased for increasing the oval fin diameter ratio(diameter of span-wise direction to diameter of longitudinal diameter) up to 50% and 45% respectively.
NUMERICAL ANALYSIS FOR TURBULENT FLOW AND AERO-ACOUSTICS AROUND A THREE DIMENSIONAL CAVITY WITH HIGH ASPECT RATIO
Mun, P.U. ; Kim, J.S. ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 7~13
Flight vehicles such as wheel wells and bomb bays have many cavities. The flow around a cavity is characterized as an unsteady flow because of the formation and dissipation of vortices brought by the interaction between the free stream shear layer and the internal flow of the cavity. The resonance phenomena can damage the structures around the cavity and negatively affect the aerodynamic performance and stability of the vehicle. In this study, a numerical analysis was performed for the cavity flows using the unsteady compressible three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equation with Wilcox's turbulence model. The Message Passing Interface (MPI) parallelized code was used for the calculations by PC-cluster. The cavity has aspect ratios (L/D) of 5.5 ~ 7.5 with width ratios (W/D) of 2 ~ 4. The Mach and Reynolds numbers are 0.4 ~ 0.6 and
, respectively. The occurrence of oscillation is observed in the "shear layer and transient mode" with a feedback mechanism. Based on the Sound Pressure Level (SPL) analysis of the pressure variation at the cavity trailing edge, the dominant frequencies are analyzed and compared with the results of Rossiter's formula. The dominant frequencies are very similar to the result of Rossiter's formula and other experimental datum in the low aspect ratio cavity (L/D = ~4.5). In the high aspect ratio cavity, however, there are other low dominant frequencies of the leading edge shear layer with the dominant frequencies of the feedback mechanism.
NUMERICAL SIMULATION OF SHOCK FOCUSING PHENOMENON BY CARTESIAN EMBEDDED BOUNDARY METHOD AND WAVE PROPAGATION ALGORITHM
Jung, Y.G. ; Chang, K.S. ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 14~20
Shock-focusing concave reflectors can have parabolic, circular or elliptic cross-sections. They produce effectively a very high pressure at the focusing point. In the past, many optical images have been obtained on shock focusing via experiments. Measurement of field variables is, however, difficult in the experiment. Using the wave propagation algorithm and the Cartesian embedded boundary method, we have successfully obtained numerical Schlieren images that appear very much like the experimental results. In addition, we obtained the detailed field variables such as pressure, velocity, density and vorticity in the unsteady domain. The present numerical results have made it possible to understand the shock focusing phenomenon in more detail than before.
NUMERICAL STUDY ON TURBULENT FLOW OVER CYLINDER USING IMMERSED BOUNDARY LATTICE BOLTZMANN METHOD WITH MULTI RELAXATION TIME
Kim, Hyung-Min ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 21~27
Immersed boundary lattice Boltzmann method (IBLBM) has been applied to simulate a turbulent flow over circular cylinder in a flow field effectively. Although IBLBM is very effective method to simulate the flow over a complex shape of obstacle in the flow field regardless of the constructed grids in the calculation domain, the results, however, become numerically unstable in high reynolds number flow. The most effective suggestion to archive the numerical stability in high Reynolds number flow is applying the multiple relaxation time (MRT) model instead of single relaxation time(SRT) model in the collision term of lattice Boltzmann equation. In the research MRT model for IBLBM was introduced and comparing the numerical results obtained by applying SRT and MRT. The hydraulic characteristic of cylinder in a flow field between two parallel plate at the range of
represented and it is also compared the drag and lifting coefficients of the cylinder calculated by IBLBM with SRT and MRT model.
THERMAL MODELING TECHNIQUE FOR GEOSTATIONARY OCEAN COLOR IMAGER
Kim, Jung-Hoon ; Jun, Hyoung-Yoll ; Han, Cho-Young ; Kim, Byoung-Soo ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 28~34
Conductive and radiative thermal model configurations of an imager of a geostationary satellite are presented. A two-plane method is introduced for three dimensional conductive coupling which is not able to be treated by thin shell plate thermal modeling technique. Especially the two-plane method is applied to massive matters and PIP(Payload Interface Plate) in the imager model. Some massive matters in the thermal model are modified by adequate correction factors or equivalent thickness in order to obtain the numerical results of thermal modeling to be consistent with the analytic model. More detailed nodal breakdown is specially employed to the object which has the rapid temperature gradient expected by a rule of thumb. This detailed thermal model of the imager is supposed to be used for analyses and test predictions, and be correlated with the thermal vacuum test results before final in-flight predictions.
LARGE EDDY SIMULATION OF TURBULENT CHANNEL FLOW AT
USING VARIATIONAL MULTISCALE METHOD
Chang, K. ; Lee, B.H. ; Yoon, B.S. ; Lee, J.S. ; Roh, M.I. ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 35~40
In the present work, LES with new variational multiscale method is conducted on the fully developed channel flow with Reynolds number, 180 based on the friction velocity and the channel half width. Incompressible Navier-Stokes equations are integrated using finite element method with the basis function of NURBS. To solve space-time equations, Newton's method with two stage predictor multicorrector algorithm is employed. The code is parallelized using MPI. The computational domain is a rectangular box of size
in the streamwise, wall normal and spanwise direction. Mean velocity profiles and velocity fluctuations are compared with the data of DNS. The results agree well with those of DNS and other traditional LES.
THRUST GENERATION AND PROPULSIVE EFFICIENCY OF A BIOMIMETIC FOIL MOVING IN A LOW REYNOLDS NUMBER FLOW
An, Sang-Joon ; Choi, Jong-Hyeok ; Maeng, Joo-Sung ; Han, Cheol-Heui ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 41~46
In this paper, the fluid dynamic forces and performances of a moving airfoil in the low Reynolds number flow is addressed. In order to simulate the necessary propulsive force for the moving airfoil in a low Reynolds number flow, a lattice-Boltzmann method is used. The critical Reynolds and Strouhal numbers for the thrust generation are investigated for the four propulsion types. It was found that the Normal P&D type produces the largest thrust with the highest efficiency among the investigated types. The leading edge of the airfoil has an effect of deciding the force production types, whereas the trailing edge of the airfoil plays an important role in augmenting or reducing the instability produced by the leading edge oscillation. It is believed that present results can be used to decide the optimal propulsion types for the given Reynolds number flow.
THE NUMERICAL SIMULATION OF HYDROGEN DIFFUSION FOR THE HYDROGEN LEAKAGE IN TUNNEL
Ahn, Hyuk-Jin ; Jung, Jae-Hyuk ; Hur, Nahm-Keon ; Lee, Moon-Kyu ; Yong, Gee-Joong ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 47~54
In the present study, a numerical simulation for the diffusion of hydrogen leakage of FCV(Fuel Cell Vehicle) in a tunnel was performed to aid the assessment of risk in case of leakage accident. The temporal and spatial distributions of the hydrogen concentration around FCV are predicted from the present numerical analyses. Flammable region of 4-74% and explosive region of 18-59% hydrogen by volume was identified from the present results. Factors influencing the diffusion of the hydrogen jet were examined to evaluate the effectiveness of tunnel ventilation system for relieving the accumulation of the leaked hydrogen gas. The distribution of the concentration of the leaked hydrogen for various cases can be used as a database in various applications for the hydrogen safety.
DEPENDENCE OF WEIGHTING PARAMETER IN PRECONDITIONING METHOD FOR SOLVING LOW MACH NUMBER FLOW
An, Y.J. ; Shin, B.R. ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 55~61
A dependence of weighting parameter in preconditioning method for solving low Mach number flow with incompressible flow nature is investigated. The present preconditioning method employs a finite-difference method applied Roe‘s flux difference splitting approximation with the MUSCL-TVD scheme and 4th-order Runge-Kutta method in curvilinear coordinates. From the computational results of benchmark flows through a 2-D backward-facing step duct it is confirmed that there exists a suitable value of the weighting parameter for accurate and stable computation. A useful method to determine the weighting parameter is introduced. With this method, high accuracy and stable computational results were obtained for the flow with low Mach number in the range of Mach number less than 0.3.
TRANSITION IN THE FLOW PAST SIDE-BY-SIDE SQUARE CYLINDERS
Choi, C.B. ; Jang, Y.J. ; Yoon, D.H. ; Yang, K.S. ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 62~70
Secondary instability in the flow past two square cylinders in side-by-side arrangements is numerically studied by using a Floquet analysis. The distance between the neighboring faces of the two cylinders (G) is the key parameter which affects the secondary instability under consideration. In this paper, we present the critical Reynolds number for the secondary instability and the corresponding spanwise wave number of the most unstable (or least stable) wave for each G. Our results would shed light on a complete understanding of the onset of secondary instability in the presence of two side-by-side square cylinders.
AN EULERIAN-BASED DROPLET IMPINGEMENT AND ICE ACCRETION CODE FOR AIRCRAFT ICING PREDICTION
Jung, S.K. ; Myong, R.S. ; Cho, T.H. ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 71~78
As a step toward accurate prediction of droplet impingement and ice accretion on aircraft, an Eulerian-based droplet impingement and ice accretion code for air flows around an airfoil containing water droplets is developed. A CFD solver based on the finite volume method was also developed to solve the clean airflow. The finite-volume-based approach for simulating droplet impingement on an airfoil was employed owing to its compatibility with the CFD solver and robustness. For ice accretion module, a simple model based on the control volume is combined with the droplet impingement module that provides the collection efficiency. To validate the present code, it is compared with NASA Glenn IRT (Icing Research Tunnel) experimental data and other well-known icing codes such as LEWICE and FENSAP-ICE. It is shown that the collection efficiency and shape of ice accretion are in good agreement with previous experimental and simulation results.
AERODYNAMIC DESIGN OPTIMIZATION OF ROTOR AIRFOIL WITH MULTIPLE CONSTRAINTS
Lee, S.M. ; Sa, J.H. ; Jeon, S.E. ; Kim, C.J. ; Park, S.H. ; Chung, K.H. ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 79~85
Aerodynamic design optimization of rotor airfoil has been performed with advanced design method for improved aerodynamic characteristics of ONERA airfoils. A multiple response surface method is used to consider various requirements in rotor airfoil design. Shape functions for mean camber line are proposed to extend possible design domain. Numerical simulations are performed using KFLOW, a Navier-Stokes solver with shear stress transport turbulence model. The present design method provides favorable configurations for the high performance rotor airfoil. Resulting optimized airfoils give better aerodynamic performance than the baseline airfoils.
A NEW PRESSURE GRADIENT RECONSTRUCTION METHOD FOR A SEMI-IMPLICIT TWO-PHASE FLOW SCHEME ON UNSTRUCTURED MESHES
Lee, H.D. ; Jeong, J.J. ; Cho, H.K. ; Kwon, O.J. ;
Journal of computational fluids engineering, volume 15, issue 2, 2010, Pages 86~94
A thermal-hydraulic code, named CUPID, has been developed for the analysis of transient two-phase flows in nuclear reactor components. A two-fluid three-field model was used for steam-water two-phase flows. To obtain numerical solutions, the finite volume method was applied over unstructured cell-centered meshes. In steam-water two-phase flows, a phase change, i.e., evaporation or condensation, results in a great change in the flow field because of substantial density difference between liquid and vapor phases. Thus, two-phase flows are very sensitive to the local pressure distribution that determines the phase change. This in turn puts emphasis on the accurate evaluation of local pressure gradient. This paper presents a new reconstruction method to evaluate the pressure gradient at cell centers on unstructured meshes. The results of the new scheme for a simple test function, a gravity-driven cavity, and a wall boiling two-phase flow are compared with those of the previous schemes in the CUPID code.