• Journal of Ship and Ocean Technology
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• v.4 no.2
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• pp.24-37
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• 2000

The purpose of this paper is to study the upstream waves in front of an advancing arbitrary hull shape in a restricted water channel. Conventionally, in a restricted water channel, shallow water effects are amplified because of the finite water depth and width. When the effects of shallow water and the restricted channel width are severe, upstream waves propagate forward from the fore-body of the advancing hull. In this study, numerical simulations are carried out for the relevant analysis of the flow phenomena by the draft variation of advancing hull in a restricted water channel. Numerical simulations are done with a finite-difference method based on the MAC scheme in a rectangular grid system.

• Journal of Wetlands Research
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• v.14 no.2
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• pp.289-301
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• 2012

Tidal artificial lake capable of inflow and outflow of seawater is planned for waterfront and eco-friendly space at Songdo, Incheon, Korea. This study for hydrodynamic behaviors of tidal artificial lake was carried out and predicted about water level and velocity within the lake corresponding to width of channel or waterway using by 1 dimensional numerical model(CEA) and 2 dimensional numerical model(FLOW2DH). As a result, the proper width, 100.0m of the channel between the lake and the open sea was calculated reasonable conclusions such as tidal phase lag and maximum velocity from CEA. Also, water level and velocity of each point within the lake was predicted and compared to the measured data from FLOW2DH. FLOW2DH was added to the gate control case for maintenance and administration purpose of the lake and obtained the results that the velocity was decreased by approximately 20% at flood and 50% at ebb than the case without gate control.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.6
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• pp.743-752
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• 1998

Experiments were performed to characterize single-phase heat transfer behavior of submerged liquid jet with multiple nozzle normally impinging on the smooth and extended surfaces. Arrays of 9 and 36 nozzles were used, with diameters of 0.5 to 2.0mm providing nozzle area ratio (AR) from 0.05 to 0.2. The square pin fin arrays were chosen as extended surfaces and the effects of geometrical parameters such as fin height, the ratio of fin width to channel width on heat transfer enhancement were examined. Single nozzle characteristics were also evaluated for comparison. The results clearly showed that heat transfer enhancement could be realized by using multiple nozzles at the constant volume flow rate. The average Nusselt number of multiple nozzle impingement on the smooth surface was correlated by the following equation : Nu/$Pr\frac{1}{3}=0.94 Re^{0.56}N^{-0.12}AR^{0.50}$The average heat transfer coefficients of multiple nozzle impingement on the extended surfaces decreased with increasing fin height and the ratio of fin width to channel width. The effectiveness of ex-tended surfaces ranged from 1.5 to 3.5 depending on the fin height, the ratio of fin width to channel width of pin fin arrays, nozzle number and nozzle area ratio.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.259-262
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• 2003

Superconducting flux flow transistor(SFFT) is based on a control of the Abrikosov vortex flowing along a channel. The induced voltage by moving of the Abrikosov vortex in SFFT is greatly affected by the thickness and width, of channel. In order to fabricate a reproducibility channel in SFFT, we have researched the variation of the critical characteristics of YBCO thin films with the etching time using ICP(Inductively coupled plasma) system. It was certified that the velocity of vortex decreased with increasing the width of channel and was saturated faster in low bias from a simulation. An etching mechanism of YBCO thin films by ICP system was also certified by AFM(Atomic Force Microscope) and by measuring the critical current density with etching time. As measurement result, we could analyze that we should optimize the etching thickness of channel part to construct a flux flow transistor with desired characteristics.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.47-52
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• 2001

Micro-injection molding and microfluidic devices with the help of MEMS technologies including the LIGA process are expected to play important roles in. micro-system industries, in particular the bioapplication industry, in the near future. Understanding fluid flows in micro-channels is important since micro-channels are typical geometry in various microfluidic devices and mold inserts for micro-injection molding. In the present study, both experimental and numerical studies have been carried out to understand the detailed flow phenomena in micro-channel filling process. Three sets of micro-channels of different thickness were fabricated and a flow visualization system was also developed to observe the filling flow into the micro-channels. Experimental flow observations were extensively made to find the effects of channel width and thickness, and effects of surface tension and volume flow rate and so on. And a numerical analysis system has been developed to simulate the filling flow into micro-channels with the surface tension effect taken into account. Discussed are the flow visualization experimental observations along with the predictability of the numerical analysis system.

• The KSFM Journal of Fluid Machinery
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• v.18 no.3
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• pp.66-73
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• 2015

This paper deals with a parametric study on boot-shaped ribs in a rectangular cooling channel. Numerical analysis of the flow and heat transfer was performed using three-dimensional Reynolds averaged Navier-Stokes equations with the Speziale, Sarkar and Gatski turbulence model. The parametric study was performed for the parameters, tip width-to rib width, tip height-to-rib height, rib height-to-channel height, and rib height-to-width ratios. To assess the cooling performance and friction loss, Numsselt number and friction factor were defined as the performance parameter, respectively. The results showed that the cooling performance and friction loss were seriously affected by the four geometric parameters.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1991-1993
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• 2002

This paper presents the PDMS surface characteristic change after the plasma process and the electroosmotic flow control technique for the two-dimensional focusing in the micro channels made of PDMS and glass. The channels are fabricated by plastic molding and micromachining technique. To observe the surface characteristic change as time elapses, we measure the contact angle of water on the surface and the velocity of the electroosmotic flow in a channel. The electric field adequate for focusing of a core flow in a confluence channel is obtained by the experiment. The computer simulation is performed to obtain the width and the depth of the core flow for several junction angles of the confluence channel.

• Journal of the Korean Institute of Navigation
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• v.22 no.3
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• pp.43-50
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• 1998

This study aims at estimating the in-and-out traffic volume and improving the main channel in Kwangyang Harbour, by utilizing measurement of congestion, i.e, the bumper model. In 2011, the traffic volume of the main channel is 11.96 ships per hour and its traffic density is evaluated 9.53% of the basic traffic capacity. Therefore the existing width of the main channel, 850m is safe enough but the channel requires the traffic separation scheme as suggested in order to secure the safe of the transit vessel.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.125-134
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• 2004

The improvement of artificial respiration method has brought about the decrease in mortality of pulmonary diseases patients. Various respiratory curative methods, inclusive of HFOV (High Frequency Oscillatory Ventilation), have been developed for more effectual and less harmful management of acute respiratory failure. However, the mechanism of gas transfer and diffusion in a bronchiole has not yet been clarified in detail. As a first approach to the problem, we measured oscillatory flows in a Y-shaped micro-channels as bronchiole model by micro Particle Image Velocimetry(micro PIV). In order to establish the fundamental technique of PIV measurements on oscillatory air flow in a micro-channel, we used about 500-nm-diameter incense smoke particles, a diode laser, a high speed camera including an objective lens, and a HFOV, which is effective technique for medical care of pulmonary disease patients, especially, infants. The bronchiole model size is that parent tube is $500\{mu}m$ width and $500\{mu}m$ depth, and daughter tubes are $450\{mu}m$ width and $500\{mu}m$ depth. From this study made on the phenomenon of fluid in micro size bronchus branch of a lung, we succeeded to get time series velocity distribution in a micro scale bronchial mode. The experimental results of velocity distribution changing with time obtained by micro PIV can give fundamental knowledge on oscillatory airflow in micro-channel.

• International Journal of Automotive Technology
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• v.8 no.6
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• pp.761-769
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• 2007

The configuration of the flow channel on a bipolar plate of a proton exchange membrane fuel cell(PEMFC) for efficient reactant supply has great influence on the performance of the fuel cell. Recent demand for higher energy density fuel cells requires an increase in current density at mid voltage range and a decrease in concentration overvoltage at high current density. Therefore, an interdigitated flow channel where mass transfer rate by convection through a gas diffusion layer is greater than the mass transfer by a diffusion mechanism through a gas diffusion layer was recently proposed. This study attempts to analyze the i-V performance, mass transfer and pressure drop in interdigitated flow channels by developing a fully three dimensional simulation model for PEMFC that can deal with anode and cathode flow together. The results indicate that the trade off between performance and pressure loss should be considered for efficient design of flow channels. Although the performance of the fuel cell with interdigitated flow is better than that with conventional flow channels due to a strong mass transfer rate by convection across a gas diffusion layer, there is also an increase in friction due to the strong convection through the porous diffusion layer accompanied by a larger pressure drop along the flow channel. It was evident that the proper selection of the ratio of channel and rib width under counter flow conditions in the fuel cell with interdigitated flow are necessary to optimize the interdigitated flow field design.