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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 20, Issue 4 - Dec 2015
Volume 20, Issue 3 - Sep 2015
Volume 20, Issue 2 - Jun 2015
Volume 20, Issue 1 - Mar 2015
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PROPULSIVE PERFORMANCE PREDICTION OF A DUCTED PROPELLER IN OPEN WATER CONDITION USING CFD
Lee, K.-U. ; Jin, D.-H. ; Lee, S.-W. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 1~6
DOI : 10.6112/kscfe.2015.20.2.001
In this study, a numerical prediction on propulsive performance of a ducted propeller in open water condition was carried out by solving Reynolds averaged Navier-Stokes(RANS) equation using computational fluid dynamics(CFD). A configuration of propeller Ka-470 inside duct 19A was considered. Hexahedral grid system was generated by dividing whole computational domain into three separate regions; propeller, duct and outer flow region. A commercial CFD software, ANSYS-CFX was used for numerical simulations. Results were compared with experimental data and showed considerable improvement in accuracy, in comparison to those from surface panel method which is based on potential flow assumption. The results also exhibited the importance of grid system within the gap between the inner surface of duct and blade tip for accurate prediction of propulsive performance of ducted propeller.
MRA AND POD APPLICATION FOR AERODYNAMIC DESIGN OPTIMIZATION
Koo, B.C. ; Han, J.H. ; Jo, T.H. ; Park, K.H. ; Lee, D.H. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 7~15
DOI : 10.6112/kscfe.2015.20.2.007
This paper attempts to evaluate the accuracy and efficiency of a design optimization procedure by combining wavelets-based multi resolution analysis method and proper orthogonal decomposition (POD) technique. Aerodynamic design procedure calls for high fidelity computational fluid dynamic (CFD) simulations and the consideration of large number of flow conditions and design constraints. Thus, even with significant computing power advancement, current level of integrated design process requires substantial computing time and resources. POD reduces the degree of freedom of full system by conducting singular value decomposition for various field simulations. In this research, POD combined Design Optimization model is proposed and its efficiency and accuracy are to be evaluated. For additional efficiency improvement of the procedure, multi resolution analysis method is also being employed during snapshot constructions (POD training period). The proposed design procedure was applied to the optimization of wing aerodynamic performance. Throughout the research, it was confirmed that the POD/MRA design procedure could significantly reduce the total design turnaround time and also capture all detailed complex flow features as in full order analysis.
NUMERICAL SIMULATION OF THE POWER-ON BASE DRAG OF A MISSILE BODY
Choi, J.H. ; Lee, E.S. ; Lee, K.S. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 16~22
DOI : 10.6112/kscfe.2015.20.2.016
The pressure is generally lower than that of the freestream at the base of a missile body due to the energy loss by the flow separation around the edge of the base. The base pressure changes in the presence of the thrust jet due to the interaction between the base flow of the missile and the jet flow. In this study, behavior of the missile base pressure by the change of the jet exit pressure and the freestream condition is investigated using the CFD(Computational Fluid Dynamics) method. Effects of the grid type and the freestream condition are tested. The results are compared with the semi-empirical predictions and the flight test data. The CFD results agree well with the flight test data. The semi-empirical predictions overestimate the base pressure when jet thrust is strong for low freestream speed.
DEVELOPMENT OF 2ND GENERATION ICE ACCRETION ANALYSIS PROGRAM FOR HANDLING GENERAL 3-D GEOMETRIES
Son, Chankyu ; Oh, Sejong ; Yee, Kwanjung ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 23~36
DOI : 10.6112/kscfe.2015.20.2.023
generation ice accretion analysis program has been developed and validated for various icing conditions. The essential feature of the
generation code lies in its capability of handling general 3-D geometry and improved accuracy. The entire velocity fields are obtained based on Navier-Stokes equations in order to take the massively separated flow field into account. Unlike
generation code, the droplet trajectories are calculated using Eulerian approach, which is adopted to yield appropriate collection efficiency even in the shadow region. For improved thermodynamic analysis on the surfaces, water film model and modified Messinger model are newly included in the present analysis. The ice shape for a given time step is obtained by considering the exact amount of ice accreted on the surface. Each module of the icing analysis code has been seamlessly integrated on the OpenFOAM platform. The developed code was validated against available experimental data for 2D airfoils and 3D DLR-F4. Due to the lack of experimental data, the computed results of DLR-F4 were compared with those obtained from FENSAP-ICE, which is state-of-the-art 3D icing analysis code. It was clearly shown that the present code produces comparable results to those of FENSAP-ICE, in terms of prediction accuracy and the capability of handling general 3-D geometries.
AERODYNAMIC STUDY ON BOBSLEIGH BUMPER SHAPE
Lee, Y.N. ; Kim, K.Y. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 37~45
DOI : 10.6112/kscfe.2015.20.2.037
A parametric study on the shapes of bobsleigh bumpers has been performed to reduce the aerodynamic drag. Effects of geometric parameters, such as leading angle of leading bumper, the ratio of minimum width to maximum width of leading bumper, the ratio of leading bumper length to trailing bumper length, trailing angle of trailing bumper, and the ratio of bumper height to installation location of bumper from the bottom of bobsleigh, on the aerodynamic performance of the bobsleigh were estimated using 3-D Reynolds-averaged Navier-Stokes equations. The turbulence was analyzed using the shear stress turbulence model. Reynolds number based on the hydraulic diameter of the external flow channel was in the range of 150,000~1,000,000. Numerical results for drag coefficient were validated compared to experimental data. Ranges of the five geometric parameters were determined according to the rule of Federation Internationale de Bobsleigh et de Tobaganning. The aerodynamic performance of the bobsleigh sled was most sensitive to the leading angle of leading bumper and the ratio of minimum width to maximum width of leading bumper.
DEVELOPMENT OF EULERIAN-GRANULAR MODEL FOR NUMERICAL SIMULATION MODEL OF PARTICULATE FLOW
Lee, T.G. ; Shin, S.W. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 46~51
DOI : 10.6112/kscfe.2015.20.2.046
In this paper, we have developed numerical model for particulated flow through narrow slit using Eulerian-Granular method. Commercial software (FLUENT) was utilized as simulation tool and main focus was to identify the effect from various numerical options for modeling of solid particles as continuos phase in granular flow. Gidaspow model was chosen as basic model for solid viscosity and drag model. And lun-et-al model was used as solid pressure and radial distribution model, respectively. Several other model options in FLUENT were tested considering the cross related effect. Mass flow rate of the particulate through the slit was measured to compare. Due to the high volume density of the stacked particulates above the slit, effect from various numerical options were not significant. The numerical results from basic model were also compared with experimental results and showed very good agreement. The effects from the characteristics of particles such as diameter, angle of internal friction, and collision coefficient were also analyzed for future design of velocity resistance layer in solar thermal absorber. Angle of internal friction was found to be the dominat variable for the particle mass flow rate considerably. More defined 3D model along with energy equation for complete solar thermal absorber design is currently underway.
INSTALLATION PARAMETERS EFFECTING ON THE WIND PROOF OF A COASTAL FOREST
Shin, J.H. ; Chang, S.M. ; Park, K.H. ; Youn, H.J. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 52~60
DOI : 10.6112/kscfe.2015.20.2.052
The objective of this research lies in the effect of installation parameters influencing on the wind proof performance of the coastal forest for damage prevention. The dissipation ratio of incident wind power is developed as an assessment index to make a lumped parameter study possible. From the real field data of East, West, and South Sea bounded on the Korean peninsula, single and double storied forests were modeled in three-dimensional shape with computer aided design, and so was done the artificial structures such as wind break, sand accumulating fence, and sand dune, etc With a commercial code ANSYS-CFX, the computational result from the comparison of dissipation ratio between single and double storied forest shows the effect of composition, and also the installation effect is investigated for artificial structures with optimal dimension of distance.
THE AERO-ACOUSTIC ANALYSIS FOR EACH PART OF DOUBLE ARM PANTOGRAPH OF HIGH SPEED TRAIN
Lee, S.A. ; Kang, H.M. ; Lee, Y.B. ; Kim, C.W. ; Kim, K.H. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 61~66
DOI : 10.6112/kscfe.2015.20.2.061
In this study, an aero-acoustic analysis around pantograph of a high speed train is performed. Computational technique and grid system is validated with wind tunnel test result and unsteady acoustic pressure data are used for analyzing noise level of each part of pantograph. FLUENT is used for flow analysis and LES(Large Eddy Simulation) is applied for analyzing turbulent flow. For acoustic analysis, Ffowcs Williams-Hawkings(FW-H) acoustics model is used and it bring the aero-acoustic characteristic of pantograph. As the result, contact strip, knee, substructure of pantograph is confirmed as a main source of aero-acoustic noise and it is dealt in various frequencies. The result is expected to help building improved grid system.
RESEARCH OF HIGH-SPEED TRAIN PANTOGRAPH SHAPE DESIGN FOR NOISE AND DRAG REDUCTION THROUGH COMPUTATIONAL ANALYSIS
Jeong, S.M. ; Lee, S.A. ; Rho, J.H. ; Kim, K.H. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 67~72
DOI : 10.6112/kscfe.2015.20.2.067
In this paper, study of high speed train pantograph arm shape and panhead cross-section for aerodynamic drag and noise reduction is performed. In previous research, it is known that knee of pantograph arm and panhead of pantogpraph are main sources of noise from high speed train pantograph. By numerical simulation using full scale pantograph model, pantograph arm and panhead optimization are performed. As a result, drag and noise are reduced at both studies about high speed pantograph.
NUMERICAL ANALYSIS OF PRESSURE PERTURBATION OF DELTA WING VORTEX FLOW AT A HIGH ANGLE OF ATTACK
Son, M.S. ; Sa, J.H. ; Park, S.H. ; Byun, Y.H. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 73~80
DOI : 10.6112/kscfe.2015.20.2.073
Delayed Detached-Eddy Simulation was conducted to investigate surface pressure coefficient distribution and surface pressure fluctuation over an ONERA 70-degree delta wing at a high angle of attack. Time-averaged surface pressure distribution is directly affected by the primary vortices, whereas the pressure fluctuation is influenced by the unsteady fluctuating boundary layer over the surface. And pressure coefficient, velocity, pressure fluctuation, and turbulent kinetic energy were analyzed along the vortex core in order to investigate the process of vortex breakdown. Consequently, strong pressure fluctuations were found where the vortex breakdown was occurred at x~620 mm. The turbulent kinetic energy abruptly increased and followed after the vortex breakdown.
ESTIMATION OF ROLL COEFFICIENT OF UNDERWATER VEHICLE USING A CALCULATION OF HYDRODYNAMIC FORCES
Kim, T.W. ; Kang, T.J. ; Park, W.G. ; Jung, C.M. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 81~87
DOI : 10.6112/kscfe.2015.20.2.081
For Underwater vehicles, Unwanted roll excursions are inevitable as they are caused by induced propeller torque, disturbances, and banking motion during turns. To estimate the manoeuvring performance of underwater vehicle, it is necessary to obtain the roll coefficient of body. This paper was covered estimation of roll coefficient of underwater vehicle using STAR-CCM+, commercial CFD(Computational Fluid Dynamics) code. The RANS equations for incompressible fluid flows was solved numerically by using a finite volume method. An MRF(Moving Reference Frame) Method was Also adopted for rotations of body. For the validation, the flow around a DARPA SUBOFF bare hull model was simulated and good agreement with experiments was obtained. And Pure roll coefficients were calculated and campared with the experimental data which were presented by Seoul National University. Finally, an underwater vehicle model with propeller was simulated and analyzed for estimation of roll coefficient variation caused by induced propeller torque.
INVESTIGATION ON MECHANICAL AND BIO-MECHANICAL PERFORMANCE OF A CENTRIFUGAL BLOOD PUMP
Chang, M. ; Moshfeghi, M. ; Hur, N. ; Kang, S. ; Kim, W. ; Kang, S.H. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 88~95
DOI : 10.6112/kscfe.2015.20.2.088
Blood pump analysis process includes both mechanical and bio-mechanical aspects. Since a blood pump is a mechanical device, it has to be mechanically efficient. On the other hand, blood pumps function is sensitively related to the blood recirculation; hence, bio-factors such as hemolysis and thrombosis become important. This paper numerically investigates the mechanical and bio-mechanical performances of the Rotaflow in the extracorporeal membrane oxygenation(ECMO), Ventricular Assist Device(VAD), and full-load conditions. The operational conditions are defined as(400[mmHg], 5[L/min.]), (100[mmHg], 3[L/min.]), and (600[mmHg], 10[L/min.]) for ECMO, VAD, and full-load conditions, respectively. The results are presented and analyzed from the mechanical aspect via performance curves, and from bio-mechanical aspect via focusing on hemolytic characteristics. Regions of top and bottom cavities show recirculation in both ECMO and VAD condtions. In addition, Eulerian-based calculation of modified index of hemolysis(MIH) has been investigated. The results demonstrate that the VAD condition has the least risk of hemolysis among the others, while the full-load condition has the highest risk.
STUDY ON GREEN WATER BEHAVIOR ON RECTANGULAR SHAPED STRUCTURE
Lee, K.N. ; Jung, K.H. ; Chae, Y.J. ; Park, I.R. ; Suh, S.B. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 96~102
DOI : 10.6112/kscfe.2015.20.2.096
In this study, the green water phenomena on rectangular shaped structure is numerically simulated by STAR-CCM+ to investigate the flow pattern including the velocity profiles in bubbly water flow. 5 phases of the formation of green water in front of and over the rectangular shaped structure is simulated at the design condition which is scaled down by 1:125 from FPSO operating in GOM. All numerical results are compared with the experimental results performed in a two dimensional wave flume. The water deformation due to the green water are obtained by the high speed CCD camera with employing the shadow graphy technique, which is allowed to take the bubbly water flow into images. A series of image taken by shadow graphy technique is analyzed with MQD method to calculate the velocity in bubbly water flow.
FLUID-BODY INTERACTION ANALYSIS OF FLOATING BODY IN THREE DIMENSIONS
Go, G.S. ; Ahn, H.T. ;
Journal of computational fluids engineering, volume 20, issue 2, 2015, Pages 103~108
DOI : 10.6112/kscfe.2015.20.2.103
Fluid-body interaction analysis of floating body with six degree-of-freedom motion is presented. In this study, three-dimensional incompressible Navier-Stokes equations are employed as a governing equation. The numerical method is based on a finite-volume approach on a cartesian grid together with a fractional-step method. To represent the body motion, the immersed boundary method for direct forcing is employed. In order to simulate the coupled six degree-of-freedom motion, Euler`s equations based on rigid body dynamics are utilized. To represent the complex body shape, level-set based algorithm is utilized. In order to describe the free surface motion, the volume of fluid method utilizing the tangent of hyperbola for interface capturing scheme is employed. This study showed three different continuums(air, water and body) are simultaneously simulated by newly developed code. To demonstrate the applicability of the current approach, two different problems(dam-breaking with stationary obstacle and water entry) are simulated and all results are validated.