• Journal of Mechanical Science and Technology
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• v.15 no.11
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• pp.1548-1554
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• 2001

Flow patterns and dynamic properties of two-stage Weis-Fogh type ship propulsion mechanism are studied by a discrete vortex method. To study mutual interference between two wings, two cases are con sidered - wing motions with the same and reverse phases. The predicted flow patterns correspond to the available flow visualization results. Time histories of thrust and drag coefficients are also calculated, and the interference between the two wings are numerically clarified.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.402-404
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• 2000

In this study, we have developed an ultrasonic separation system for plant cells and its operating conditions in terms of voltage, flow rate and concentration were examined. For plant cell, the operation of ultrasonic separator highly depended on concentration of cells. Holding capacity highly depended on flow rate in chamber. Optimum voltage was 30V in high density culture

• Wind and Structures
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• v.5 no.2_3_4
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• pp.177-192
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• 2002

Computation solutions for the flow around a cube, which were generated as part of the Computational Wind Engineering 2000 Conference Competition, are compared with full-scale measurements. The three solutions shown all use the RANS approach to predict mean flow fields. The major differences appear to be related to the use of the standard $k-{\varepsilon}$, the MMK $k-{\varepsilon}$ and the RNG $k-{\varepsilon}$ turbulence models. The inlet conditions chosen by the three modellers illustrate one of the dilemmas faced in computational wind engineering. While all modeller matched the inlet velocity profile to the full-scale profile, only one of the modellers chose to match the full-scale turbulence data. This approach led to a boundary layer that was not in equilibrium. The approach taken by the other modeller was to specify lower inlet turbulent kinetic energy level, which are more consistent with the turbulence models chosen and lead to a homogeneous boundary layer. For the $0^{\circ}$ case, wind normal to one face of the cube, it is shown that the RNG solution is closest to the full-scale data. This result appears to be associated with the RNG solution showing the correct flow separation and reattachment on the roof. The other solutions show either excessive separation (MMK) or no separation at all (K-E). For the $45^{\circ}$ case the three solutions are fairly similar. None of them correctly predicting the high suctions along the windward edges of the roof. In general the velocity components are more accurately predicted than the pressures. However in all cases the turbulence levels are poorly matched, with all of the solutions failing to match the high turbulence levels measured around the edges of separated flows. Although all of the computational solutions have deficiencies, the variability of results is shown to be similar to that which has been obtained with a similar comparative wind tunnel study. This suggests that the computational solutions are only slightly less reliable than the wind tunnel.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.4
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• pp.59-67
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• 2016

Numerical simulations have been performed to investigate thrust characteristics of a through-type pintle nozzle with or without flow separation at various operating altitudes. The low Reynolds number $k-{\varepsilon}$ with compressibility correction proposed by Sarkar are applied. The detail flow structures are observed and static pressures along nozzle wall are compared with experimental results. The flow separation in the pintle nozzle disappears and jet plume strongly expands as its operating altitude increases. To evaluate the thrust characteristics, the momentum term and pressure term of thrust are analyzed. Thrust and thrust coefficient at altitude 20 km are about 10% more than them at the ground 0km.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.3
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• pp.529-561
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• 2014

The two-phase turbulent flow past an interface-piercing circular cylinder is studied using a high-fidelity orthogonal curvilinear grid solver with a Lagrangian dynamic subgrid-scale model for large-eddy simulation and a coupled level set and volume of fluid method for air-water interface tracking. The simulations cover the sub-critical and critical and post critical regimes of the Reynolds and sub and super-critical Froude numbers in order to investigate the effect of both dimensionless parameters on the flow. Significant changes in flow features near the air-water interface were observed as the Reynolds number was increased from the sub-critical to the critical regime. The interface makes the separation point near the interface much delayed for all Reynolds numbers. The separation region at intermediate depths is remarkably reduced for the critical Reynolds number regime. The deep flow resembles the single-phase turbulent flow past a circular cylinder, but includes the effect of the free-surface and the limited span length for sub-critical Reynolds numbers. At different Froude numbers, the air-water interface exhibits significantly changed structures, including breaking bow waves with splashes and bubbles at high Froude numbers. Instantaneous and mean flow features such as interface structures, vortex shedding, Reynolds stresses, and vorticity transport are also analyzed. The results are compared with reference experimental data available in the literature. The deep flow is also compared with the single-phase turbulent flow past a circular cylinder in the similar ranges of Reynolds numbers. Discussion is provided concerning the limitations of the current simulations and available experimental data along with future research.

• Analytical Science and Technology
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• v.26 no.4
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• pp.262-267
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• 2013

Gravitational field-flow fractionation (GrFFF) is a separation technique that utilizes earth's gravity as the external field. GrFFF is a convenient tool for the size and/or density-based separation of micron-sized particles of various origins. In this study, GrFFF was employed for size-based separation of oyster mushroom spores. Oyster mushroom spores have smooth surface and are of cylindrical to narrow kidney-shapes with 5 to 12 im in longer dimension and 3 to 4 im in shorter dimension, as was confirmed by optical microscope (OM). GrFFF conditions were optimized for separation and characterization of spores by varying the channel flow rate from 0.5 to 1 mL/min. During the GrFFF elution of the spores, 3 fractions were collected to confirm the growth of oyster mushroom spore. The collected fractions were incubated for 30 days in water to examine the influence of the size on the growth of the spores. Results suggested that the oyster mushroom spores collected at the middle part of the GrFFF fractogram grew faster than those collected at the beginning or at the end of the fractogram.

• Journal of the Korean Society for Marine Environment & Energy
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• v.4 no.2
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• pp.52-60
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• 2001

The need to control the oil content in oily bilge water discharges to meet the increasing stringent seawater pollution standards has led to the development of gravity type separators. Among the several gravitational methods, a plate type oily water separator can be used as an assistant equipment for the oil filtering system to meet the present IMO standard of 15 ppm, because it is believed to be an efficient method dealing with a large amount of rich oil with high specific gravity. The purpose of this paper is to examine the efficiency of oil/water separation with the characteristics of separating plate arrangement. An experimental study was carried out to analyse an efficient treatment oil-water mixture with variation of operating parameters, including flow rates, inlet oil concentrations and the height between the plates. The experimental results show that the height between the plates has a significant effect on the separation efficiency. The best efficiency was acquired when the ration of the height between the plates the plates to distance(H/Ci) was 2 with lower inlet oil concentration and lower flow rate.

• Membrane Journal
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• v.16 no.3
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• pp.196-203
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• 2006

A flue gas emission known to cause an acid rain, containing sulfur dioxide, is tightly controlled by a regulation. The membrane contactor could be one of the alternatives which might be useful technologies for better performance of desulfurization. The fundamental sulfur dioxide separation data were obtained by a flat membrane contactor so that they could be utilized for the full scale membrane contactor. The separation of sulfur dioxide was measured in terms of the concentration of NaOH absorbent, the concentration of sulfur dioxide, the feed flow rate and different membrane materials. As the concentration of absorbent increased, the removal efficiency increased. By increasing the concentration of sulfur dioxide, the removal efficiency decreased. As the feed flow rate increased, it was observed that the removal efficiency decreased. Finally, the effect of the membrane material on separation was found to be negligible.

• Analytical Science and Technology
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• v.37 no.2
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• pp.123-129
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• 2024

We present a rapid method for the determination of Cs, Sr, and Ba, heat generators found in highly active liquid wastes, by gas-pressurized extraction chromatography (GPEC) using a column containing a cation-exchange resin. GPEC is a microscale column chromatographic technique that uses a constant flow rate of solvent (0.07 mL/min) with pressurized nitrogen gas supplied through a valve. In particular, because this method uses a small sample volume (a few hundred microliters), it produces less chemical waste and allows for faster separation compared to traditional column chromatography. In this study, we evaluated the separation of Cs, Sr, and Ba using GPEC. The eluate from the column (GPEC or conventional column chromatography) was quantitatively analyzed using inductively coupled plasma-mass spectrometry to measure the column recovery and precision. The column reproducibility of the proposed GPEC system (RSDs of recoveries) ranged from 2.7 to 4.1 %, and the column recoveries for the three elements ranged from 72 to 98% when aqueous HCl was used as the eluent. The GPEC results are slightly different in efficiency and separation resolution compared to those of conventional column chromatography because of the differences in the eluent flow rate as well as the internal diameter and length of the column. However, the two methods had similar recoveries for Cs and Sr, and the precision of GPEC was improved by two-fold. Remarkably, the solvent volume required for GPEC analysis was five times lower than that of the conventional method, and the total analysis time was 11 times shorter.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2420-2425
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• 2007

Heat transfer from three-dimensional heat-generating modules was investigated. A simulated electronic module in an array configured with dummy module elements was used to measure the average heat transfer coefficients. Various module arrangements were tested using module spacings of 0.85 and 1.15 cm for six Reynolds numbers ranging from 500 to 975. The results show that a module placed in-line with and upstream of a heated module results in the heat transfer enhancement due to a high level in turbulence prompted by upstream modules. The highest enhancement occurs when the separation distance between modules is close to the module length in the flow direction. Flow visualization reveals laminar flow on the front of the first module, slow recirculation regions on the sides parallel to the air stream, and turbulence on the back side. It appears that the first module serves to trip the air stream and produce a high level of turbulence, which enhances the heat transfer rate downstream.