• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1744-1748
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• 2004

It is important to measure precisely the size and velocity of micro-bubbles used in various field. The synchrotron X-ray micro-imaging technique was employed to measure the size and velocity of micro-bubbles moving in an opaque tube simultaneously. Phase contrast images were obtained at interfaces of micro-bubbles between water and air due to their different refractive indices. The X-ray micro-imaging technique was found to measure an optical fiber with an accuracy of 0.2%. Micro-bubbles of $10{\sim}60{\mu}m$ diameter moving upward in an opaque tube (${\phi}=2.7mm$) were tested to measure bubble size and up-rising velocity. For DI water, the measured velocity of micro-bubbles is nearly proportional to the square of bubble size, agreed well with the theoretical result. In addition, the synchrotron X-ray micro-imaging technique can measure accurately the size and velocity of several overlapped micro-bubbles.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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• pp.1222-1230
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• 2009

A theoretical model was developed to compute the effect of a bubble layer in reducing the radiation noise generated by a force applied on an infinite flat plate considering the noise of multi-bubbles. Using the model, the effectiveness of a bubble layer in reducing the structure-borne noise of the plate was evaluated to consider various parameters such as the source noise levels, the thickness of bubble layers, the volume fractions and the frequency characteristics of bubbly fluids. Considering the noise of multi-bubbles, the actual reduction effect of radiation noise using a bubble layer was expected in cases of high source levels, high volume fractions of bubbles and large thickness of the bubble layer above the resonance frequency of the bubble layer. Accordingly, it is recommended that the thickness of a bubble layer, the source noise level and the characteristics of bubbly fluids should be optimized cautiously to maximize noise reduction effects.

• Journal of the Korea Society of Computer and Information
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• v.29 no.3
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• pp.91-98
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• 2024

In this paper, we present a particle-grid blending framework based on a geometric approach to efficiently represent opaque ice spheres with air bubbles. The water temperature is diffused through the grid and the air bubbles represented inside the ice through the particles. To solve the problem of previous methods that generate noisy dissolved air fields, we use levelsets to lighten the algorithm, i.e., the number of active particles and the initial amount of dissolved oxygen can be used to efficiently control the termination conditions of heat diffusion. We also extend the previous dissolved air field method, which only computes near air bubbles, to transparent regions to represent realistic ice spheres, and introduce a levelset-based approach to accurately compute the orientation of particles. As a result, the method presented in this paper is about three times faster than the existing methods and shows visually improved visualization of opaque ice spheres, which can be used in the field of representing physical virtual ice forms.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.222-227
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• 2004

Flotation processes involve the use of very small bubbles (micro-bubbles) to separate particles from water. The process has become a good alternative to sedimentation, especially where the particles are small or of low density. Although the flotation process commences with a collision between particles and bubbles, most research has been focused only on the characteristics of the particles. In this paper, recent theoretical and experimental research on the characteristics of bubbles is summarized. The effect on the collision efficiency of the size and charge of bubbles is calculated through trajectory analysis. The size and charge of bubbles are measured under different conditions and the ramifications of the results are discussed. The results may lead to a better understanding and optimization of the existing process. In particular, we discuss an idea that a new advanced flotation process might be possible by the modification of the characteristics of the bubble alone or of both bubble and particle.

• Journal of Drive and Control
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• v.16 no.1
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• pp.1-6
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• 2019

The use of micro bubbles in industrial fields has been increasing in the recent years., particularly micro-bubble sterilization and water purification effects. Various methods have been developed for the generation of micro-bubbles. Depending on the method of generating bubbles, the micro-bubbles can be roughly classified into saturation molding, cavitation and rotation flow types. The objective of this study was to use ventilated tube type as a method of generating micro-bubbles in order to purify large amount of water quality such as lakes and reservoirs. This method shows a difference in efficiency in which micro-bubbles are generated depending on the contact ratio of gas to liquid. The study also investigated the optimal gas liquid contact ratio by applying various orifice methods and investigated the optimum condition of micro-bubble generation by gas Based on this, a technology to develop a micro-bubble generator with a venturi type nozzle shape that has a high water purification effect was developed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.2
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• pp.142-151
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• 1991

In the present investigation, it has been proposed to utilize a direct contact heat exchanger as an evaporator to solve the difficulties such as scaling, corrosion and law thermal efficiencies, associated with the conventional evaporator. Liquified nitrozen was utilized as a working fluid to investigate basic natures of bubble dynamics in the evaporator, and spray nozzles were adopted to inject liquified nitrozen into the spray column with varying flow rates of dispersed phase fluids. Experimentations were carried out in the range of $6.54{\times}10^{-4}kg/s$ - 0.030 kg/s for dispersed phase flow rates with one, three and five nozzle holes. Observing the bubble dynamics for the evaporator the feasibility of utilizing a direct contact heat exchanger as a LNG evaporator has been evaluated. The results show that no eruption phenomena was observed in the present investigation with $LN_2$ and the interface between $N_2$ bubbles and water was fully turbulent. It is believed that the high injection velocity of $LN_2$ through the spray nozzles provide good mixing effects for both heat and mass transfers between water and $N_2$ bubbles. Ice was formed on the surface of the spray nozzle for higher $LN_2$ flow rates. However, even in this case, it is observed that the ice was detached as soon as it was formed. Under the present experimental conditions, the shapes of $LN_2$ bubbles were in the spherical-cap region according to the Clift, Grace and Weber Graphs. The height of foam region caused by the breakup of larger bubbles keeps increasing with high injection velocities until it reaches it's maximum height.

• Journal of the Korean Society of Visualization
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• v.15 no.2
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• pp.48-58
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• 2017

To analyze bubbles generated by an ABB (Air Bubble Barrier), we developed image processing procedure and statistical analysis method. Air was discharged from 5 mm nozzle as swarm form at the bottom of 1 m3 water tank. Flow rates of discharged air are ranged from 2 L/min to 20 L/min and these are corresponding to Reynolds number of 1766-17663. Rise velocity of bubble is extracted by using image process pretending intrusive method. Mean equivalent velocity was calculated using void fraction weighting factor. Bubble diameter is obtained and compared with correlations in the literature. Also, we present a correlation according to the result of this study. Mean velocity and mean diameter of bubbles increase with increasing gas Reynolds number. But these parameters show an asymptotic trend when they approach to high Reynolds number.

• The KSFM Journal of Fluid Machinery
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• v.2 no.3 s.4
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• pp.37-44
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• 1999

In a screw-type centrifugal pump, the pump head deteriorates from single-phase flow to the choke due to an increased air entrainment at a wide tip clearance compared to that of a narrow tip clearance. Moreover, at a narrow tip clearance, the pump head became partially higher in a two-phase flow than that of a single-phase flow near the best efficiency point in low void fraction region. Therefore, we observed the internal flow pattern by using a stroboscope and we measured the mean size of bubbles from the images obtained with a high speed camera. Then, we investigated the influences of the mean size of bubbles, tip clearances and flow patterns on pump performance.

• Journal of Biosystems Engineering
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• v.30 no.5 s.112
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• pp.312-317
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• 2005

A flow injection type biosensor was tested to confirm the performance of a batch and a continuous type flow injection unit. Reproducibility and consistence of the biosensor were investigated to determine the effect of pulsations and air bubbles, and the applicability of on-line monitoring. The air bubbles affected the performance of the sensor irrespective of the location, and also the pulsations of the pump influenced the performance of the sensor. The applicability of on-line motoring was accepted as the result of the repeated and long-term measurements.

• Journal of Korea Water Resources Association
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• v.38 no.4 s.153
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• pp.313-321
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• 2005

The elimination and erosion of cohesive sediments in port and reservoir water can so far be processed only with mechanical evacuation methods under extreme energy expenditure. The so-called flushing jets do not serve the purpose because they cannot set the material spaciously in motion despite high shear stresses at the bed. Therefore this study aims to examine the resuspension of the deposited fine material($Al_{2}O_3$) under presence of gas bubbles in order to decreased cohesive sediments in multipurpose dam, port and lakes. In the case of laboratory trial important parameters considered are supplied amount of air and the consolidation time of the solid materials. With increasing gas content alumina remains in suspension at high pH values in the laboratory test, where the particles fall mote rapidly without air addition.