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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 11, Issue 4 - Dec 2006
Volume 11, Issue 3 - Sep 2006
Volume 11, Issue 2 - Jun 2006
Volume 11, Issue 1 - Mar 2006
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DESIGN-ORIENTED AERODYNAMIC ANALYSES OF HELICOPTER ROTOR IN HOVER
Jung H.J. ; Kim T.S. ; Son C.H. ; Joh C.Y. ;
Journal of computational fluids engineering, volume 11, issue 3, 2006, Pages 1~7
Euler and Navier-Stokes flow analyses for helicopter rotor in hover were performed as low and high fidelity analysis models respectively for the future multidisciplinary design optimization(MDO). These design-oriented analyses possess several attributes such as variable complexity, sensitivity-computation capability and modularity which analysis models involved in MDO are recommended to provide with. To realize PC-based analyses for both fidelity models, reduction of flow domain was made by appling farfield boundary condition based on 3-dimensional point sink with simple momentum theory and also periodic boundary condition in the azimuthal direction. Correlations of thrust, torque and their sensitivities between low and high complexity models were tried to evaluate the applicability of these analysis models in MDO process. It was found that the low-fidelity Euler analysis model predicted inaccurate sensitivity derivatives at relatively high angle of attack.
THERMAL ANALYSIS OF SURFACE HEAT PIPE INSTALLED PANEL OF GEOSTATIONARY SATELLITE
Jun H.Y. ; Kim J.H. ;
Journal of computational fluids engineering, volume 11, issue 3, 2006, Pages 8~13
The north panel of a geostationary satellite is used as one of the main radiators, on which communication equipment or bus equipment are installed. The thermal control of panel is designed by using embedded heat pipes and surface heat pipes (or external heat pipes) to spread out heat dissipated from equipment all over the radiator evenly and finally to reject the heat to the space through the radiator efficiently. This panel is also divided by several areas based on the operating temperature and dissipation of equipment in order to increase heat rejection capability of radiator. The thermal analysis is carried out for the hot case, Winter Solsitce EOL (End Of Life), in order to validate thermal design of the panel utilized 6 surface heat pipes and 8 embedded heat pipes. The sensitivity studies for the heat pipe failure case and no heat pipe case are performed and compared to its normal state. The heat transport capability of heat pipe is also obtained from these calculations.
A NUMERICAL ANALYSIS ON THE COLLISION BEHAVIOR OF WATER DROPLETS
Nam Hyun-Woo ; Baek Je-Hyun ;
Journal of computational fluids engineering, volume 11, issue 3, 2006, Pages 14~21
A numerical simulation of the binary collision dynamics of water drops for size ratios of 1 and 0.75, for the Weber number range of 5 to 100, and for all impact parameter is reported. Two different types of separating collisions, namely reflexive and stretching separations, are identified. A numerical method is based on a fractional-step method with a finite volume formulation and the interface is tracked with Volume of Fluid(VOF) method, including surface tension. Numerical results for size ratios 1 and 0.75 are reasonablely compared with Ashgriz and Poo's experimental results.
A NUMERICAL STUDY ON THE CHARACTERISTICS OF ASYMMETRIC VORTICES AND SIDE FORCES ON SLENDER BODIES AT HIGH ANGLES OF ATTACK
Jung S.K. ; Jung J.H. ; Myong R.S. ; Cho T.H. ;
Journal of computational fluids engineering, volume 11, issue 3, 2006, Pages 22~27
Flow around a guided missile in high maneuver, i.e. at a high angle of attack, shows complex phenomena. It is well known that even in geometrically symmetric conditions the flow around a missile at high angles of attack can generate unexpected large side forces and yaw moments due to asymmetric vortices. In this paper, a CFD code (FLUENT) based on the Navier-Stokes equations was used for the numerical analysis to find a suitable numerical mechanism for generation of asymmetric vortices. It is shown that a numerical technique of applying different surface roughness to a specific area of the missile nose surface gives the best fit in comparison with the experimental results. In addition, a numerical investigation of variations of side forces and pressure distributions with angle of attack and roll angle was conducted for the purpose of identifying the source of vortex asymmetries.
NUMERICAL STUDY ON FLOW OVER CIRCULAR CYLINDER USING NO SLIP BOUNDARY TREATMENT
Kang Jung-Ho ; Kim Hyung-Min ;
Journal of computational fluids engineering, volume 11, issue 3, 2006, Pages 28~36
NSBT(No Slip Boundary Treatment) is a newly developed scheme for the treatment of a no slip condition on the solid wall of obstacle in a flow field. In our research, NSBT was used to perform LBM simulation of a flow over a circular cylinder to determine the flow feature and aerodynamics characteristic of the cylinder. To ascertain the applicability of NSBT on the complex shape of the obstacle, it was first simulated for the case of the flow over a circular and square cylinder in a channel and the results were compared against the solution of Navier-Stokes equation. The simulations were performed in a moderate range of Reynolds number at each cylinder position to identify the flow feature and aerodynamic characteristics of circular cylinder in a channel. The drag coefficients of the cylinder were calculated from the simulation results. We have numerically confirmed that the critical reynolds number for vortex shedding is in the range of 200
250. For the gap parameter
= 2 cases at Re > 240, the vortex shedding were symmetric and it resembled the Karmann vortex. As the cylinder approached to one wall, the vorticity significantly reduced in length while the vorticity on the other side elongated and the vorticity combined with the wall boundary-layer vorticity. The resultant
by LBM concurred with the results of DNS simulation performed by previous researchers.
NUMERICAL VISUALIZATION OF THE MIXING PATTERN IN A LID-DRIVEN-CAVITY FLOW
Suh Y.K. ;
Journal of computational fluids engineering, volume 11, issue 3, 2006, Pages 37~45
In this study we present the numerical methods that can be used in visualization of the flow and mixing patterns in a cavity driven by a top lid. The basic flow field within the cavity has been obtained by using a simple numerical scheme. The invariant manifold also called unstable manifold was then attained to represent the mixing pattern within the cavity. It was shown that care must be taken in calculating the trajectories of the fluid particles especially near corners of the cavity. The numerical results show excellent agreement with those obtained experimentally by other research group.
EFFECT OF THE ZETA POTENTIAL CONTROL BY THE TRAPEZOIDAL ELECTRODES IN A MICROCHANNEL ON ENHANCEMENT MIXING-PERFORMANCE
Suh, Y.K. ; Heo, H.S. ; Kang, J.F. ;
Journal of computational fluids engineering, volume 11, issue 3, 2006, Pages 46~51
This paper presents the numerical results of fluid flow and mixing in a microfluidic device for electro-osmotic flow (EOF) with an trapezoidal electrode array on the bottom wall (ETZEA). Differently from previous EOF in a channel which only transports fluid in colloidal system. ETZEA can also be utilized to mix a target liquid with a reagent. In this study we propose a method of controlling fluid flow and mixing enhancement. To obtain the flow and mixing characteristics, numerical computations are performed by using a commercial code, CFX-10, and a self-made code LBM-D. It was found that the flow near the trapezoidal electrode in the ETZEA is of 3-D complex flows due to the zeta potential difference between the trapezoidal electrode and channel walls, and as a consequence the hetrogeneous zeta potential on the electrodes plays an important role in mixing the liquid.
EFFECTS OF PLACEMENT OF A TORUS PLATE COVER ON AIR FLOW IN A SPINNER EQUIPMENT
Kwak H.S. ; Yang J.O. ; Lee S.W. ; Park S.H. ;
Journal of computational fluids engineering, volume 11, issue 3, 2006, Pages 52~58
A numerical investigation is made of air flow in a spinner equipment used for cleanning and drying flat display panels. A unique feature of the spinner under question is the placement of a torus plate cover over the rotating plate. The turbulent flow is driven by rotation of a large disk and suction by the exhaust system connected to vacuum chamber. The flow is modelled as an axisymmetric two-dimensional flow and computation is conducted by using the FLUENT package with a version of k-
turbulence model. The required capacity of the exhaust system is assessed numerically. The usefulness of the cover in controlling air flow circulation is examined. A computational trouble shooting is attempted to resolve the problem of panel rising which occurred in real experiment.
BASE DRAG PREDICTION OF A SUPERSONIC MISSILE USING CFD
Lee Bok-Jik ;
Journal of computational fluids engineering, volume 11, issue 3, 2006, Pages 59~63
Accurate prediction of a supersonic missile base drag continues to defy even well-rounded CFD codes. In an effort to address the accuracy and predictability of the base drags, the influence of grid system and competitive turbulence models on the base drag is analyzed. Characteristics of some turbulence models is reviewed through incompressible turbulent flow over a flat plate, and performance for the base drag prediction of several turbulence models such as Baldwin-Loman(B-L), Spalart-Allmaras(S-A), k-
model is assessed. When compressibility correction is injected into the S-A model, prediction accuracy of the base drag is enhanced. The NSWC wind tunnel test data are utilized for comparison of CFD and semi-empirical codes on the accuracy of base drag predictability: they are about equal, but CFD tends to perform better. It is also found that, as angle of attack of a missile with control fins increases, even the best CFD analysis tool we have lacks the accuracy needed for the base drag prediction.
A COMPUTATIONAL STUDY ABOUT THE ASYMMETRIC AERODYNAMIC EVOLUTION AROUND A CIRCULAR CYLINDER CAUSED BY A MOVING WALL
Jung J.Y. ; Chang J.W. ;
Journal of computational fluids engineering, volume 11, issue 3, 2006, Pages 64~70
A Computational study was carried out in order to investigate the moving wall effect of a circular cylinder at a Reynolds number of
. The viscous-incompressible Navier-Stokes equations and Spalart-Almaras turbulent model of the commercial CFD code were adopted for this numerical analysis. The moving wall was set parallel with the freestream, and moving speed was equal to the freestream velocity. The gap ratio is defined as the distance ratio between the circular cylinder diameter and the height from the moving wall. The results show that there is vortex shedding over the critical gap ratio and aerodynamic loads including amplitude and the Strouhal number change according to the gap ratio.