• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.267-274
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• 2009

Breakup and spray formation of pressure-swirl liquid jets injected into a low-speed convective-flow are experimentally investigated. Effects of the cross-flows on the macroscopic and microscopic spray parameters are optically measured in terms of jet Weber number and liquid-to-gas momentum ratio. The liquid stream undergoes Rayleigh jet breakup at lower jet Weber numbers and a liquid sheet isn't formed because of the weak radial velocity in the swirl jet. At higher jet Weber numbers, the macroscopic spray parameter is a very weak function of the momentum ratio but the effect of the convection on the microscopic spray parameter is significant through the secondary breakup with increasing in the liquid-to-gas momentum ratio. The convective-flow promotes bag/plume breakup and the spray formation, and its effect is more distinct at higher momentum ratio.

• Ocean Systems Engineering
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• v.10 no.3
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• pp.317-332
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• 2020

This study examines the behaviors and properties of discharged liquid CO₂ from a long elastic pipe moving with a vessel for the oceanic CO₂ sequestration by considering pipe dynamics and vessel motions. The coupled vessel-pipe dynamic analysis for a typical configuration is done in the frequency and time domain using the ORCAFLEX program. The system's characteristics, such as vessel RAOs and pipe-axial-velocity transfer function, are identified by applying a broadband white noise wave spectrum to the vessel-pipe dynamic system. The frequency shift of the vessel's RAO due to the encounter-frequency effect is also investigated through the system identification method. Additionally, the time histories of the tip-of-pipe velocities, along with the corresponding discharged droplet size and Weber numbers, are generated for two different sea states. The comparison between the stiff non-oscillating pipe with the flexible oscillating pipe shows the effect of the vessel and pipe dynamics to the discharged CO₂ droplet size and Weber number. The pipe's axial-mode resonance is the leading cause of the fluctuation of the discharged CO₂ properties. The significant variation of the discharged CO₂ properties observed in this study shows the importance of considering the vessel-pipe motions when designing oceanic CO₂ sequestration strategy, including suitable sequestration locations, discharge rate, towing speed, and sea states.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.5
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• pp.395-403
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• 1991

The purpose of this investigation was to characterize nucleate boiling and burn-out heat flux for rectangular free jet with saturated water impinging perpendicularly and upward against a flat uniform heat flux surface. Heat flux measured for Reynolds number based on rectangular nozzle width and for aspect ratio. The result of nucleate boiling heat transfer was presented nondimensional experimental equation including Nusselt, Boiling, Subcooling, Reynolds and Weber number. The effect of aspect ratio of heated surface in the burn-out heat flux had not appeared distinctly. But for the same aspect ratio, burn-out heat flux increased linearly with increment of nozzle exit velocity.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.5
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• pp.1388-1394
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• 2016

This paper presents a experimental study of two-phase flow boiling of FC-72 in multi channels. Flow boiling heat transfer coefficients are obtained with mass flux ranging from 152.9 to $353.9kg/m^2s$ and heat flux from 5.6 to $46.1kW/m^2$. The experimental results show that the heat transfer is governed by nucleate boiling mechanism in the low heat flux region. However, it is found that the effects of nucleate boiling and forced convection boiling are combined as the heat flux increases. A new correlation to predict the heat transfer coefficient is developed by using the dimensionless number such as Reynolds number, Weber number, boiling number. This correlation shows good predictive accuracy against the measured data.

• Journal of the Korean Mathematical Society
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• v.57 no.5
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• pp.1103-1118
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• 2020

In this paper, we investigate a family of graphs associated to collections of arcs on surfaces. These multiarc graphs naturally interpolate between arc graphs and flip graphs, both well studied objects in low dimensional geometry and topology. We show a number of rigidity results, namely showing that, under certain complexity conditions, that simplicial maps between them only arise in the "obvious way". We also observe that, again under necessary complexity conditions, subsurface strata are convex. Put together, these results imply that certain simplicial maps always give rise to convex images.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.6
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• pp.811-818
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• 2001

The wave characteristics for a non-reacting high-speed liquid jet were investigated using a linear stability theory. In this study, 2-D incompressible viscid momentum equation for a liquid jet was considered, and the effects of injection parameters, such as Weber number, Reynolds number, and density ratio, on the wave characteristics were investigated. With the wavelength obtained from the stability analysis, the atomization model was suggested. The droplet sizes after breakup were determined by the wavelengths of fast growing waves, and the mass of the shed droplets was determined by the breakup time derived by ORouke et al. It was found that in comparison with measurements of diesel fuel spray, the results of calculation had a similar trend of the decrease of overall SMD with the increase of Reynolds number.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2568-2573
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• 2008

A drop impact on the liquid film/pool generates several phenomena such as the drop floating, bouncing, formation of vortex ring, jetting, bubble entrapment and splashing. These phenomena depend on the impact velocity, the drop size, the drop properties and the liquid film/pool thickness. These parameters can be summarized by four main dimensionless parameters; Weber number, Ohnesorge number, Froude number and non-dimensional film/pool thickness. In the present study, the phenomena of the splashing and bubble entrapment due to the drop impact on the liquid film/pool were numerically investigated by using a Level Set method for the sharp interface tracking of two distinct phases. After the drop impact, the splashing phenomena with the crown formation and spreading were predicted. Under the specific conditions, the bubble entrapment at the base of the collapsing cavity due to the drop impact was also observed. The numerical results were compared to the available experimental data showing good agreements.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.5
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• pp.1-9
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• 2012

The gas jet from a coaxial porous injector for two-phase flows is discharged from the porous surface, which encloses the center liquid jet, and the gas and liquid jet interact with each other physically. The wall injected gas jet transfers the radial momentum effectively while the radial gas jet develops to axial jet, and the performance of atomizing and mixing can be improved. In this study, the Weber number and the ratio of momentum flux were controlled by changing the gas injection area and the mass flow rate of the gas jet, and a study on the spray characteristics at the cold-flow test using water and air simulant was performed. It is concluded that the radial momentum transfer concept of a coaxial porous injector gives a positive effect on the atomization and mixing of the two-phase spray.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.59-70
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• 2021

An experimental study was conducted to observe the spray characteristics for different flow rates and rotating speeds of a rotating fuel nozzle of a slinger combustor. The water spray ejected from the nozzle orifice was visualized using a high-speed camera and a light source. It was confirmed that the atomization was improved, as the flow rate decreased and rotating speed increased. The characteristic maps for the spray characteristics and performance parameters showed that the aerodynamic Weber number and the liquid-air momentum flux ratio were associated with the liquid primary breakup, and the liquid-air momentum flux ratio and Rossby number were closely correlated with the liquid ejection mode.

• Applied Chemistry for Engineering
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• v.4 no.3
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• pp.537-543
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• 1993

The effect of agitation on liquid-liquid dispersion was investigated in an immisible liquid phase(n-hexane/water) system. Four different types of six-bladed turbine impellers were used: a flat blade, two screen blades and a solid edged 60 mesh screen blade. We found that the extent of dispersion of organic phase and power consumption of agitator were decreased in the order of flat, solid edged, 60 mesh, and 40 mesh blades at same agitation speed. And the minimum agitation speed for complete dispersion of organic phase was increased with increasing volume fraction of organic phase. Also, mean diameter of liquid droplets of dispersed phase was decreased with increasing agitation speed and it was increased in the order of solid edged, flat, 60 mesh, and 40 mesh screen blades at same agitation speed. At complete dispersion, the minimum power consumption was not vary significantly with impeller blade types, but the solid edged screen blade impeller gave the smallest and uniform sizes of liquid droplets, and it had a good performance for liquid-liquid dispersion. In this condition, Power number was not affected by Reynolds number and it was constant in turbulent flow region, and Sauter mean diameter($d_{32}$) of liquid droplets was expressed as a function of volume fraction of organic phase(${\phi}$) and Weber number($N_{We}$) as follows: $d_{32}/D=a(1+b{\phi})N_{We}{^{-0.6}}$.