• The KSFM Journal of Fluid Machinery
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• v.10 no.4
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• pp.39-46
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• 2007

In large pump station, vortex generation such as free-surface vortex and submerged vortex occurring around pump intake, or at bell-mouth inlet has been an important flow characteristics which should be considered always to keep away the suction of air-entrained or cavitated flow. In this study, a commercial CFD code was used to predict accurately the vortex generation for the specified intake design. These result shows the preliminary result of submerged vortex prediction for the Turbo-machinery Society of Japan Sump Test CFD standard model. At bottom wall, air volume fraction (red color) was found in a large scale to explain the submerged vortex generation at particular operation and configuration condition. And these indicate the free surface formation behind the bell mouth. Particularly, non-uniform approaching flow is a major parameter to govern the occurrence of the free-surface vortex. Futhermore the comparison between turbulence ($k-{\epsilon}$ & $k-{\omega}$ model) mode were executed in this study.

• The KSFM Journal of Fluid Machinery
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• v.12 no.4
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• pp.14-22
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• 2009

The head-capacity curves for pumps developed by the pump manufacturer are based on tests of a single pump operating in a semi-infinite basin with no close walls or floors and with no stray currents. Therefore, flow into the pump intake is with no vortices or swirling. However, pump station designers relying on these curves to define the operating conditions for the pump selected sometimes meet the reductions of capacity and efficiency, as well as the increase of vibration and additional noise, which were caused by air-entered flow in the pump station. From this background, the authors are carrying out a systematic study on the flow characteristics of intakes within a sump of pump station model. Multi-intake sump model with anti-submerged vortex device basin is designed and the characteristics of submerged vortex is investigated in the flow field by numerical simulation. In this study, a commercial CFD code is used to predict the vortex generation in the pump station accurately. The analysed results by CFD show that the vortex structure and effect of anti-submerged vortex device are different at each pump intake channel.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.3
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• pp.463-469
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• 2012

The efficiency of the flow mixed pump installed within the bell-mouth in the sump is reduced by the flow characteristics of around intakes. Strong submerged vorticies can be successfully suppressed by installing an AVD(anti-submerged vortex device) on the bottom of pump intake channel just below the bell-mouth. Sump model with AVD device basin is designed and the characteristics of submerged vortex is investigated in the flow field by numerical simulation. In this study, a commercial CFD code is used to predict the efficiency of the pump with the AVD installation in the pump station accurately.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.3
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• pp.151-158
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• 2003

The study of velocity fields and vortex generation around the submerged breakwater can be utilized as materials related to understanding of wave dissipation mechanism, sediment transport, and stability of structure. In the present study, two-dimensional numerical wave flume, based on the VOF method to trace free surface, developed by Kim et al.(2001, 2002) was used to numerically simulate velocity fields and vortex generation around the impermeable submerged breakwater installed at the uniform bottom. Especially, the characteristics of vortex generation due to the geometry of the structure and incident wave conditions are examined through the analysis of averaged-velocity fields around the impermeable submerged breakwater. From the numerical simulations, it is confirmed that a counter clockwise vortex is formed in front of the structure and a clockwise vortex develops behind the structure. Also, incident wave height and period have an sensitive effect on the strength of vortex.

• Journal of the Korean Society of Visualization
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• v.11 no.2
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• pp.34-40
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• 2013

A flow visualization near submerged nozzle of solid rocket motor was conducted by experiments. A numerical simulation was also performed to reveal detailed phenomena. Radial cold flow simulating hot gas was introduced by a porous grain model which was manufactured by perforated steel plates. The grain model was mounted in high-pressure chamber which has quartz glass at the top of the grain model. From the high-speed images, a rotating vortex was observed and the two type of counter-rotating momentums were generated in numerical results. The rotating momentum was generated at the fin-slot grain because of unbalance between high-velocity flow from slots and low-velocity flow from fin-bases. As a result, roll torques can be produced by the rotating vortex tube.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.1
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• pp.31-39
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• 2011

In order to suggest the methodology for achieving anti-vortex device within multi pump intake well, CFD(Computational Fluid Dynamics) simulation were conducted for two alternative suggestions. Multi-intake sump model with anti-vortex device basins were designed and the characteristics of submerged vortex were investigated in the flow field by numerical simulation. From the results of simulations, to install the horizontal plate and vertical cross plates within basins were effective for preventing air-induction vortex.

• Resources Recycling
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• v.6 no.4
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• pp.24-30
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• 1997

The recent trend of recycle of mold scrap is to make high quality secondary ingot which can be used as raw malerial undcr intensive control of scrap. In this study, recycle of aluminum chlp generated atter machinmg process of castings was performed by vortex melting melhod Vortex melting technique was adopted for chip mclting process. The condition far optimal vortcx depth was decided using water mndellng experiment varying the shape, location, rotating speed of stlircr and watcr levcl. Before melting, chips were preheated at room temperame, 200, 300, $ 400^{\circ}C$and then submerged in the mirldle of vortex. The lecovery rale depending on the temperature was examined. As a result vortex depth was influenccd only by shape and rotating speed of stirrer, and the hlghest recovery rate oI 97% was obta~nedw hcn the submerged chip was preheated at $300^{\circ}C.$

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.582-588
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• 2005

An experimental study to establish a standard of sump model test of pump station was implemented. Comparison of foreign standard was also performed. Configuration condition around a bell mouth suction intake was easily adjusted by 3-axis traversing system and partition allocation. Operational condition was also varied widely to give accurate test data. PIV was also introduced to produce Quantitative analysis of flow field such as free-surface vortex and submerged vortex occurring in the model test. More detailed vortex behaviors were represented by PIV analysis.

• The KSFM Journal of Fluid Machinery
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• v.15 no.5
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• pp.60-66
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• 2012

One of commonly physical phenomena encountered in pump sump systems in which its significant influence to the hydraulic performance of pump system plays an important role in the field of fluid engineering, is the appearance of free surface and submerged vortices. In this paper, a study of the vortices behavior and their formative mechanism of asymmetry is considered in this paper by using numerical approach. The Reynolds-Averaged Navier-Stokes (RANS) equations and k-omega Shear Stress Transport turbulence model used to describe the properties of turbulent flows, in company with VOF multiphase model, are implemented by Fluent code with multi-block structured grid system. In the numerical simulation, the calculated elevation of air-water interface and vortex core contours are used to classify visually surface vortices as well as submerged vortices. It is shown that the free surface vortex is identified by the concavity of liquid region from the free surface and swirling flow at that own plane. To investigate the distinctive behavior of these vortices corresponding to each given flow rate at the same water level, some numerical testing of them are considered here in such a manner that the flow pattern of surface vortex are obtained similarly to the obtained results from experiment. Furthermore, the influence due to the change of grid refinement and the variation of depth of the concavity are also considered in this paper. From that, these influential factors will be implemented to design a good pump sump with higher performance in the future.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1863-1868
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• 2003

Decades of studies of geophysical flow have unveiled that the flow downstream of obstacles in stratified flow consists of attached wake and strong internal waves, or separated, fluctuating wake and persistent late wakes. Among unique and interesting characteristics of the stratified flow past obstacles is the generation of coherent vortex the late wake far downstream of the object. Unlike in homogeneous fluid, the flow field downstream self-develops coherent vortex even after diminishing of the near wake, no matter how small the stratification is. This paper present a computational approach to simulate the generation of the coherent vortex structure in late wake of a moving sphere submerged in weakly stratified fluid. The results are in consistent with several experimental observations and the vortex stretching mechanism is employed to explain the process of coherence.