• Journal of the Society of Naval Architects of Korea
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• v.42 no.6 s.144
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• pp.637-643
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• 2005

A new novel Whipping Factor is proposed as a measure of the ship damage potential due to an underwater explosion bubble pulse. The factor was derived from the relationships among the charge weight, its depth and the fluid acceleration due to pulsating gas bubble. From the whipping response analyses for three uniform Timoshenko beams with similar characteristics of real naval surface ships, we have confirmed the maximum bending moment responses of beams due to whipping are almost same if the applied whipping factor is constant regardless of the charge weights and depths, which could validate the proposed whipping factor.

• 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 Korean Society of Water and Wastewater
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• v.12 no.4
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• pp.53-58
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• 1998

Dissolved Air flotation (DAF) has become increasingly important in the field of drinking water treatment, however, the research to investigate the mechanism of collision between bubble and particle has been limited. The electrostatic repulsion forces between them are critical to collide with each other. Zetapotential of bubble and particle show their electrostatic condition. In this research, a setup to measure the zetapotential of rising microbubble is made using electrophoresis method and measured ZP of bubble in our Lab. The results show the effect of pH on zetapotential of bubble. The findings from this research are compared with other results. It will he helpful to understand and explain the mechanism of collisions between bubble and particle on different conditions of bubble charge in DAF process.

• Tunnel and Underground Space
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• v.25 no.1
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• pp.46-55
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• 2015

A water tube with detonating cord was devised to control the blast dust. Water diffusion experiments with different detonating cord positions were conducted during the series of experiments to optimize the design parameters of the tube. Images from high speed camera were analyzed to evaluate the results. AUTODYN program was adopted to simulate the diffusion process of water and compared with the images. Diffusion of water shows cross flow in case of external charge while the internal case shows radial flow. A bubble ring was formed during the numerical analysis of internal charge case as occurred in underwater blast. An additional bubble ring was formed by the reflection pressure from the ground. And the Weber number was determined as sufficient for spray atomization performance of the water tube.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.6
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• pp.2023-2035
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• 1996

In the present study, the characteristics of the electrical deformation of a bubble and a drop under a uniform electric field have been investigated to understand EHD heat transfer enhancement by an electric field. The deformation of the bubble and the drop have been studied theoretically using an electric normal stress acting on their interfaces and assured by the numerical analysis and the experiment. From the variation of bubble volume and free energy, it is found that a bubble is compressed in an electric field and free energy had larger value with increasing W and the permittivity of a dielectric fluid. The electric normal stress induced on the interface of the bubble and the drop is different. Because of the surface charge induced at the drop interface, the electric normal stress acting on the drop is much larger than that of the bubble. The drop is, therefore, deformed much more than the bubble. In addition, the experimental and numerical results show that the aspect ratio and the contact angle of the bubble increase with increasing W.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.5
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• pp.271-277
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• 2020

Recoverability and vulnerability of navy ships under underwater explosion are critical verification factors in the acquisition phase of navy ships. This paper aims to establish numerical analysis techniques for the underwater explosion of navy ships. Doubly Asymptotic Approach (DAA) Equation of Motion (EOM) of primary shock wave and secondary bubble pulse proposed by Geers-Hunter was introduced. Assuming a non-compressive fluid, reference solution of the DAA EOM of Geers-Hunter using Runge-Kutta method was derived for the secondary bubble pulse phase with an assumed charge conditions. Convergence analyses to determine fluid element size were performed, suggesting that the minimum fluid element size for underwater explosion analysis was 0.1 m. The spherical and cylindrical fluid domains were found to be appropriate for the underwater explosion analyses from the fluid domain shape study. Because the element size of 0.1 m was too small to be applied to the actual navy ships, a very slender beam with the square solid section was selected for the study of fluid domain existence effect. The two underwater explosion models with/without fluid domain provided very similar results in terms of the displacement and stress processes.

• Metals and materials international
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• v.24 no.6
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• pp.1327-1332
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• 2018

In this study, a novel approach to the explosive synthesis of titanium carbide (TiC) is discussed. Nonstoichiometric $TiC_x$ powder was produced via the underwater explosion of a Ti powder encapsulated within a spherical explosive charge. The explosion process, bubble formation, and synthesis process were visualized using high-speed camera imaging. It was concluded that synthesis occurred within the detonation gas during the first expansion/contraction cycle of the bubble, which was accompanied by a strong emission of light. The recovered powders were studied using scanning electron microscopy and X-ray diffraction. Submicron particles were generated during the explosion. An increase in the carbon content of the starting powder resulted in an increase in the carbon content of the final product. No oxide byproducts were observed within the recovered powders.

• 전기의세계
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• v.29 no.8
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• pp.532-537
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• 1980

Effect of Argon and Sulfur hexafloride in the transformer oil are experimented under non-uniform A.C. electric field. The result has shown that the corona frequency and corona charge quantity in liquid dielectrics were varied with gas condition in the oil and affected by the additives. SF$_{6}$ that has the effects of pressure and electrical negative characteristic is the most effective. The corona is considered to be the breakdown of bubble produced by gas contained in the oil or by dissociated ion of the oil molecules.s.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.573-579
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• 2004

Electroflotation, which is used as an alternative to sedimentation, is a separation treatment process that uses small bubbles to remove low-density particulates. Making allowances for recent collision efficiency diagram based on trajectory analysis, it is necessary to tailor zeta potential of bubbles that collide with negatively charged particles. In this paper, the study was performed to investigate the effects of magnesium and aluminium ions on zeta potential of bubbles. And, it was studied to find out factors which could affect the positively charged bubbles. Consequently, zeta potential of bubbles increased both with higher concentration of metal ions and in the acidic pH value. And, a probable principle that explained the procedure of charge reversal could be a combined mechanism with both specific adsorption of hydroxylated species and laying down of hydroxide precipitate. It also depended on the metal ion concentration in the solution to display its capacity to control the bubble surface.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1993.05a
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• pp.70-78
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• 1993

Heat pipes, applied to flat plate solar collectors, have a long and slender configuration with relatively low heat flux on the evaporator. Such a heat pipe has a tendency to build-up a liquid pool at the lower half of evaporator zone, and at this pool occurs such complicated phenomena of evaporation and fluid dynamics as superheat, sudden generation of bubble, its likely explosive growth process and flooding etc. In the present study, we tried to solve those problems by means of adjusting the two principle design parameters, liquid fill charge and wick length, using 4 heat pipes and 3 thermosyphons, with different values of parameter respectively. The corresponding results can be summarized as followings, - The thermal conductance of heat pipes was largely improved by el eliminating wick from adiabatic and condenser zone. - But on evaporator zone wick is inevitable to reduce behavior of the build -up of liquid pool , where arise diverse internal complex phenomena. - The liquid fill charge should have to be increased by 10∼20％ more than the quantity to saturate the wick.