• Korea-Australia Rheology Journal
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• v.19 no.2
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• pp.67-73
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• 2007

A finite volume method (FVM) base on the SIMPLE algorithm as the pressure correction strategy and the traditional staggered mesh is used to investigate steady, fully developed flow of Oldroyd-3-constant fluids through a duct with square cross-section. Both effects of the two viscoelastic material parameters, We and ${\mu}$, on pattern and strength of the secondary flow are investigated. An amusing sixteen vortices pattern of the secondary flow, which has never been reported, is shown in the present work. The reason for the changes of the pattern and strength of the secondary flow is discussed carefully. We found that it is variation of second normal stress difference that causes the changes of the pattern and strength of the secondary flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.1
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• pp.72-80
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• 2004

Steady flow of an ER (electro-rheological) fluid in a two-dimensional electrode channel is studied by using FEM. Hydrodynamic interactions between the particles and the fluid are calculated by solving the Navier-Stokes equation combined with the equation of motion for each particle, where the multi-body electrostatic interaction is described by using point-dipole model. Motion of the particles in the ER fluid is elucidated in conjunction with the mechanisms of the flow resistance and the increase of viscosity. The ER effects have been studied by varying the Mason number and volume fraction of particles. These parameters have an influence on the formation of the chains resulting in the changes of the fluid velocity and the effective viscosity of ER fluids.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1142-1149
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• 2003

The present study describes a numerical analysis for simulation of the sloshing of flows with free-surface which contained in a rectangular tank moving in harmonic or pitching motion. The VOF function, representing the volume fraction of a cell occupied by the fluid, is calculated for each cells, which gives the location of the free-surface filling any some fraction of cells with fluid. The time-dependent changes of free-surface height are used for visualization subject to several conditions such as fluid height, horizontal acceleration, sinusoidal motion, and viscosity. The free-surface heights were used for comparing wall-force, which is caused by sloshing of flows. Damping effects by baffles were extensively investigated for various conditions in terms of baffle shape and position.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.11
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• pp.125-131
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• 1995

Pneumatic System has been mainly used as main equipment for actuation and control of fluid force in manufacturing industry. For velocity control of piston, meter-out restriction method is used in many cases. In this systems, meter-out restriction method is adopted for analysing the Dynamic Charging and Discharging Process which is Variable Volume Chamber. Experiments has been conducted for different supply pressure condition. As a experimental result, charge side chamber pressure rises to supply pressure rapidily and discharge side chamber pressure decreases. Also, when the air in the cylinder is discharged, tempdrature of air decreases steeply. Restriction of the Cylinder sometimes freeze and it dose not function. The result will be useful for the analysis of pneumatic system.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.479-486
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• 2016

The efficient steam drum should be required to reduce carbon oxide emissions and heat recovery in oxygen converter hood system. However, steam generation is limited to the time of the oxygen blowing period, which is intermittent or cyclical in operation of steel-making process. Thus, steam drum should be optimized for an effective steam generation during the oxygen blowing portion of the converter cycle. In this study, a three-dimensional computational fluid dynamics (CFD) model has been developed to describe the impacts of changing various operating conditions and geometric shape on thermo-fluid characteristics and performance of the steam drum. This model encompasses not only fluid flow and heat transfer but also evaporation and condensation at the interfacial surface in the steam drum by using VOF (Volume of Fluid) method. To validate the prediction performance of this model, comparison of the steam flow rate between numerical and experimental result has been performed, resulting in the accuracy of the relative error by less than 3.2%.

• Journal of Ocean Engineering and Technology
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• v.21 no.2 s.75
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• pp.12-21
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• 2007

As the economy grows and the population increases, we need to develop our coastal area and make use of it for various purposes. Specifically, investigation of the wave interactions on and around the vertical cylinders is very important in the design of the offshore or coastal structures. The nonlinear potential analysis developed so far, although very useful, has been found to be limited in application, as strong nonlinear waves generated by the interference between multilayered cylinders and wave impact forces by breaking waves can hardly be estimated. In this study, using a 3-Dimensional volume tracking method VOF(Volume of Fluid), based on Namer-Stokes equations, was developed to simulate highly nonlinear effects, such as breaking waves at the interface or complicated interference waves among structures. A numerical method for nonlinear interaction wave and vertical cylinders is newly proposed. The wave forces and wave transformations computed by the newly proposed numerical simulation method were compared to the other researcher's experimental results, and the results agree well. Based on the validation of this study, this numerical method is applied to the two vertical cylinders to discuss their nonlinear wave forces and wave transformations, according to the variations of separate distance of vertical cylinders.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.2
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• pp.91-100
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• 2006

The purpose of this study was to validate alternative method by using non-carcinogenic, and less toxic solvents than NIOSH analytical method 5524 for measuring the airborne MWFs in workplaces. In laboratory tests, the ETM solvents(mixture of same volume for ethyl ether, toluene, and ethanol) were selected. The alternative method of analyzing MWFs, referred to as the ETM solvent extraction method, showed 0.04 mg/sample as LOD, and 0.15 mg/sample as LOQ. The analytical precision (pooled CV, coefficient of variation) of the ETM solvent extraction method for analyzing the straight, soluble, semisynthetic, and synthetic metalworking fluid was 1.5%, 2.0%, 2.6%, 1.6%, respectively, which was similar to the precision (2.6%) of NIOSH analytical method (NIOSH 0500) for total dust. The analytical accuracy by recovery test, spiked mass calculated as extractable mass, was almost 100%. As the result of storage stability test, metalworking fluid samples should be stored in refrigerated condition, and be analyzed in two weeks after sampling. The 95% confidence limit of the estimated total standard error for the ETM solvent extraction method for analyzing the straight, soluble, semisynthetic, and synthetic metalworking fluid was ${\pm}12.6%$, ${\pm}12.5%$, ${\pm}14.0%$, and ${\pm}13.6%$, respectively, which satisfied the OSHA sampling and analytical criteria.

• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1209-1212
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• 1999

The entropies and chemical potentials of hard-sphere solutes solvated in hard-sphere solids were calculated by Monte Carlo method using the radial free-space distribution function. This method is based on calculating the entropy by comparing the free volume of a molecule with that of an ideal gas, and is applicable even when the size of solute is very large and the solvent is a solid. When the diameter of hard-sphere solute is small the solute molecule behaves as like as a fluid in solid structures, but when the diameter of solute becomes large, a fluid-to-solid phase transition takes place. The fluid-to-solid phase transition occurs at the region of the smaller size of solute with the more increase of solvent density. The least square fit values of analytical form of the radial free-space distribution functions of solute molecules are presented for future uses.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.4
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• pp.317-324
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• 2011

When a ship proceeds in confined water, like canal, the water ahead of ship is pushed by hull. This pushed water returns to the side and under the hull, and this returned water will make fluid velocity higher at the side and under the hull, compared to the case in the infinite water depth. Due to the higher velocity, the pressure under the hull will decrease, resulting in the ship drop. This phenomenon is called "ship squat" and ship squat will result in various marine accidents. In this paper, for predicting ship squat, numerical calculation was carried out using commercial CFD code, FLUENT. To confirm wave pattern profile around the ship, VOF(Volume of Fluid) method was applied. The calculated results were compared with other paper's results and empirical methods.

• The KSFM Journal of Fluid Machinery
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• v.9 no.3 s.36
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• pp.14-21
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• 2006

Leakage reduction through annular type seals of turbomachinery is necessary for enhancing their efficiency and the precise prediction method of seal leakage is needed. The analysis based on Bulk-flow concept has been mainly used in predicting seal leakage. However, full Navier-Stokes Equations with turbulent model derived in the seal flow passage have to be solved for improving the prediction of seal leakage. FLUENT 6 which is commercial CFD(Computational Fluid Dynamics) code based on FVM(Finite Volume Method) and SIMPLE algorism has been used to analyze leakage of various non-contact-type seals in this presentation. Comparing with the results of Bulk-flow model analysis and experiment, the result of CFD analysis shows good agreement with that of existing theoretical analysis for the incompressible grooved seal and compressive plain and staggered seal. The CFD analysis also shows improvement on the leakage prediction of the incompressible plain seal and compressive see-through-type labyrinth seal.