• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.36-44
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• 2000

The flow at the impeller exit is important to validate engineering design and numerical analysis of pumps. We installed axisymmetric collector instead of the volute casing, so there is no interaction between the impeller and casing. A hot-film probe and a high response pressure transducer are used to investigate the flow at impeller exit and vaneless diffuser region for design and off design flow rate. For a single suction centrifugal pump of low specific speed, the flow field such as velocity, flow angle, and total pressure are measured by traversing the probe across the vaneless diffuser. These data can be used for performance prediction, design, and numerical analysis of pumps.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2127-2132
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• 2003

A computational study is performed to better understand the choke phenomenon of unsteady gas flow through a critical nozzle. The axisymmetric, unsteady, compressible, Navier-Stokes equations are solved using a finite volume method. In order to simulate the effects of back pressure fluctuations on the critical nozzle flow, a forced sinusoidal pressure wave is assumed downstream the exit of the critical nozzle. It's frequency is 20kHz and amplitude is varied below 15% of time-mean back pressure. The results obtained show that for low Reynolds numbers, the unsteady effects of the pressure fluctuations can propagate upstream of the throat of critical nozzle, and thereby giving rise to applicable fluctuations of mass flow through the critical nozzle. The effect of the amplitude of the excited pressure fluctuations on the choke phenomenon is discussed in details.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.597-600
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• 2002

In general, the function of intake structure, whether it be a open channel, a fully wetted tunnel, a sump or a tank, is to supply an evenly distributed flow to a pump station. An even distribution of flow, characterized by strong local flow, can result in formation of surface or submerged vortices, and with certain low values of submergence, may introduce air into pump, causing a reduction of capacity and efficiency, an increase in vibration and additional noise. Uneven flow distribution can also increase or decrease the power consumption with a change in total developed head. To avoid these sump problems pump station designers are considered intake structure dimensions, such as approaching upstream, baffle size, sump width, width of pump cell and so on. From this background, flow characteristics of intake within sump are Investigated numerically to obtain the optimal sump design data. The sump model is designed in accordance with HI code.

• Membrane and Water Treatment
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• v.1 no.2
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• pp.159-169
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• 2010

The effect of external recycle on the performance of dialysis in countercurrent-flow rectangular membrane modules was investigated both theoretically and experimentally. Theoretical analysis of mass transfer in parallel-flow device with and without recycle is analogous to heat transfer in parallel-flow heat exchangers. Experiments were carried out with the use of a microporous membrane to dialyze urea aqueous solution by pure water. In contrast to a device with recycle, improvement in mass transfer is achievable if parallel-flow dialysis is operated in a device of same size with recycle which provides the increase of fluid velocity, resulting in reduction of mass-transfer resistance, especially for rather low feed volume rate.

• Journal of ILASS-Korea
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• v.11 no.1
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• pp.39-47
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• 2006

In-cylinder flows in a motored 3.5L four-valve SI engine were investigated quantitatively using three-component LDV system, to determine how engine configuration affects the flow field. The purpose of this work was to develop quantitative methods which correlate in-cylinder flows to engine performance. For this study, two distinct intake/piston arrangements were used to examine the flow characteristics. Quantification of the flow field was done by calculating two major parameters which are believed to characterize adequately in-cylinder motion. These quantities were turbulent kinetic energy(TKE) and tumble ratio in each plane at each crank angle. The results showed that in-cylinder flow pattern is dominated by the intake effects and two counter rotating vortices, developed during the intake stroke, produced relatively low tumble ratio. Therefore, the applicability of these quantities should be carefully considered when evaluating characteristics resulting from the complex in-cylinder flow motions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.366-372
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• 1999

The deformation behavior of commercial stainless steels under hot rolling conditions was investigated by means of hot compression tests performed in the temperature range 800$^{\circ}C$ to 1200$^{\circ}C$. The measured flow stress-strain curves were analyzed by using a simple flow stress model. It was found that the reference strength of stainless steels are much higher than that of carbon steel and that nitrogen and molybdenum alloying greatly increases flow stress of austenitic stainless steel. Ferritic and duplex stainless steel showed comparatively low flow stresses. The flow stress model, which correlates the flow stress with temperature and strain rate, was applied to predict roll forces during hot-plate rolling of stainless steels.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.494-499
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• 2011

One of the devices to prevent separated flow over a wing or a flap at high angle of attack is a vortex generator. In the present work, we numerically study the flow around a low-profile or micro vortex generator whose height is less than local boundary layer thickness which can delay separation with a minimum drag penalty owing to its very small wetted surface area. As a first step toward a parametric study to efficiently design this MVG flow control system, we simulate the flow around a single MVG on a flat plate. For the simulation, we employ OpenFOAM with Launder-Sharma ${\kappa}$-epsilon model. The analysis results are validated by comparing with experimental results of a rectangular MVG at an angle of attack of 10 degrees whose height is 20% of local boundary layer. Important results and aspects of this numerical study are discussed. We also simulate the flow around rectangular, triangular and trapezoidal MVGs and the results are compared

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.7
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• pp.937-945
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• 1998

The purpose of this paper is to investigate the relationship between pressure recovery and turbulent characteristic value of velocity and pressure, in the case where a swirling flow streams into a conical diffuser. The results of both measurements of the wall pressure fluctuation and velocity fluctuation revealed them to role the large part of the total pressure loss of the flow. The cause of the fluctuation of flow was showed to be the flow separation at the inlet of diffuser at low intensity of swirl, but the flow of diffuser center was instable at high intensity of swirl. The static pressure recovery depends strongly on the magnitude of the turbulent energy in the diffuser, and that this magnitude of the turbulent energy varies as the intensity of swirl at the diffuser inlet.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.269-271
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• 2012

To investigate emission characteristics of laminar premixed CH4/air flame, combustion experiments were conducted at three flow rates (5.3L/min, 10.6L/min, 15.5L/min) with changing the combustor pressure(-30Kpa-30Kpa). It was found that with increasing flow rate, NOx emission increased in high pressure condition, while decreased in low pressure condition; and the emission of CO decreased with increasing flow rate. For the influence of pressure, emission of NOx increased with increasing pressure regardless of flow rates, while CO emission decreased on the contrary.

• Korea-Australia Rheology Journal
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• v.20 no.1
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• pp.35-42
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• 2008

An inverse ferrofluid composed of micron sized polymethylmethacrylate particles dispersed in ferrofluid was used to investigate the effects of test duration times on determining the flow curves of these materials under constant magnetic field. The results showed that flow curves determined using low duration times were most likely not measuring the steady state rheological response. However, at longer duration times, which are expected to correspond more to steady state behaviour, we noticed the occurrence of plateau and decreasing flow curves in the shear rate range of $0.004\;s^{-1}$ to ${\sim}20\;s^{-1}$, which suggest the presence of nonhomogeneities and shear localization in the material. This behaviour was also reflected in the steady state results from shear start up tests performed over the same range of shear rates. The results indicate that care is required when interpreting flow curves obtained for inverse ferrofluids.