• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.1-7
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• 2011

The paper concerns numerical study of fully developed laminar flow of a Newtonian water and non-Newtonian fluids, 0.2% aqueous of sodium carboxymethyl cellulose(CMC) solution in eccentric annuli with combined bulk axial flow and inner cylinder rotation. Pressure losses and skin friction coefficients have been measured when the inner cylinder rotates at the speed of 0~200 rpm. A numerical analysis considered mainly the effects of annular eccentricity and inner cylinder rotation. The present analysis has demonstrated the importance of the drill pipe rotation and eccentricity. In eccentricity of 0.7 of a Newtonian water, the flow field is recirculation dominated and unexpected behavior is observed. it generates a strong rotation directed layer, that two opposing effects act to create two local peaks of the axial velocity. The influences of rotation, radius ratio and working fluid on the annular flow field are investigated.

• Journal of Ocean Engineering and Technology
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• v.35 no.2
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• pp.121-130
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• 2021

In this study, a computational fluid dynamics (CFD) simulation based on an Eulerian-Eulerian approach was used to evaluate the mixing performance of a mud agitator through the distribution of bulk particles. Firstly, the commercial CFD software Star-CCM+ was verified by performing numerical simulations of single-phase water mixing problems in an agitator with various turbulence models, and the simulation results were compared with an experiment. The standard model was selected as an appropriate turbulence model, and a grid convergence test was performed. Then, a simulation of the liquid-solid multi-phase mixing in an agitator was simulated with different multi-phase interaction models, and lift and drag models were selected. In the case of the lift model, the results were not significantly affected, but Syamlal and O'Brien's drag model showed more reasonable results with respect to the experiment. Finally, with the properly determined simulation conditions, a multi-phase flow simulation of a mud agitator was performed to predict the mixing time and spatial distribution of solid particles. The applicability of the CFD multi-phase simulation for the practical design of a mud agitator was confirmed.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.12 no.2
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• pp.121-133
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• 2014

If the spent fuels or the high-level radioactive wastes can be disposed of in the depth of 3~5 km and more stable rock formation, it has several advantages. For example, (1)significant fluid flow through basement rock is prevented, in part, by low permeability, poorly connected transport pathways, and (2)overburden self-sealing. (3)Deep fluids also resist vertical movement because they are density stratified and reducing conditions will sharply limit solubility of most dose-critical radionuclides at the depth. Finally, (4) high ionic strengths of deep fluids will prevent colloidal transport. Therefore, as an alternative disposal concept to the deep geological disposal concept(DGD), very deep borehole disposal(DBD) technology is under consideration in number of countries in terms of its outstanding safety and cost effectiveness. In this paper, for the preliminary applicability analyses of the DBD system for the spent fuels or high level wastes, the DBD concepts which have been developed by some countries according to the rapid advance in the development of drilling technology were reviewed. To do this, the general concept of DBD system was checked and the study cases of foreign countries were described and analyzed. These results will be used as an input for the analyses of applicability for DBD in Korea.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.834-841
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• 2005

Polyethylene glycol esters (PEG-esters) were synthesized by condensation reaction of dicarboxylic acid such as adipic acid and sebacic acid and several PEGs. The PEG-esters were analyzed by FT-IR, $^1H-NMR$ and HPLC for structure analysis, and by GPC for molecular weight. Through the analysis of surface tension, critical micelle concentration (CMC), aluminum contact angle of water solution containing the PEG-ester, the synthetic PEG-esters are proven to exhibit surfactant properties. The surface tension ranged from 45 to 50 dyn/cm depended on the concentration and structures of the PEG-esters. The surface tension of PEG-esters with sebacic acid moiety and short polyoxyethylene unit resulted in lower value than that of PEG-ester with adipic acid moiety and long polyoxyethylene unit. The CMC of water solution containing 2.5 wt% PEG-ester with sebacic acid moiety estimated at $0.9{\times}10^{-5}{\sim}5.3{\times}10^{-3}mol/L$ depended on the structures of PEG-esters. The CMC of PEG-esters with long polyoxyethlene unit showed a higher value than that of PEG-esters with short polyoxyethylene unit. Meanwhile, the CMC of PEG-esters with adipic acid moiety was not distinct due to their high hydrophilic character. As the results of contact angle and cutting time aginst aluminum, the contact angle ranged from $45^{\circ}$ to $53^{\circ}$ depended on the concentration of PEG-esters. The cutting time of aluminum showed the shortest value at CMC, but the longest value above CMC. This fact indicates that the CMC of PEG-esters is a very important factor in drilling aluminum.

• Tunnel and Underground Space
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• v.12 no.4
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• pp.277-283
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• 2002

This experimental study concerns the characteristics of a helical flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one is rotating. The pressure losses and skin friction coefficients have been measured for the fully developed flow of Non-Newtonian fluid, aqueous solution of sodium carbomethyl cellulose (CMC) and bentonite with inner cylinder rotational speed of 0~400 prm. Also, the visualization of helical flows has been performed to observe the unstable waves. The results of present study reveal the relation of the Reynolds number Re and Rossby number Ro with respect to the skin friction coefficients. In somehow, they show the existence of flow instability mechanism. The pressure losses increase as the rotational speed increases, but the gradient of pressure losses decreases as the Reynolds number increases in the regime of transition and turbulence. And the increase of flow disturbance by Taylor vortex in a concentric annulus with rotating inner cylinder results in the decrease of the critical Reynolds number with the increase of skin friction coefficient.

• Economic and Environmental Geology
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• v.20 no.2
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• pp.97-106
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• 1987

The geology of the Bupyeong mine area is consisted of Precambrian Gyeonggi gneiss complex and Mesozoic igneous rocks; i.e., pyroclastic rocks, intrusive breccia, granite and felsic porphyries which were formed during a Jurassic to early Cretaceous resurgent caldera evolution. Granites are not observed on the surface and in the underground of the mine. Bupyeong silver deposits occur as stockworks of base metal sulfides- minor silver minerals-quartz - carbonate veinlets, hosted by pyroclastic rocks and intrusive breccia at the southwestern margin of the caldera. Silver occurs mainly as native silver, and other silver minerals, minor in quantity, are argentite, tetrahedrite-freibergite, pyrargyrite, polybasite, canfieldite and dyscrasite. The average grade of silver ore is about 180g/t Ag. Discrimination of silver ore from the country rocks depends largely on the chemical analyses of rock samples taken every two meters from tunnels, diamond-drilling cores and mining stopes, because silver minerals are hardly observed in the ore by crude eye, and silver orebodies do not properly coincide with the concentrated zone of base metal sulfides which were precipitated at the earlier stage than the stage of precipitation of native silver. General characteristics of the loci of the silver orebodies are as follows; (1) The host rocks of orebodies are pyroclastic rocks and intrusive breccia. (2) Many of the orebodies are distributed around Gyeonggi gneiss complex. Especially where the paleotopography of gneiss complex shows a gradual slope, the basal stratigraphic horizon of the pyroclastic rocks unconformably overlying the gneiss complex offered a favorable loci of high grade ore. (3) $N5^{\circ}W$ to $N15^{\circ}$ E-striking faults played an important role in the localization of the orebodies. (4) Conduits of intrusive breccia within the gneiss complex, through which the intrusive breccia intruded into the upper pyroclastic rocks, exist beneath most of the main orebodies. This suggests that the conduits of intrusive breccia served as channelways for the migration of ore fluids.

• Economic and Environmental Geology
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• v.20 no.1
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• pp.19-34
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• 1987

The Nokdong As-Zn deposit, located 28 km south of Kyeongju City, Southern Korea, has been investigated by a deep drilling programme. The mineralized zone is roughly 290m long and 180m wide at surface and is hosted in a pipe diatreme infilled with poor to well bedded felsic volcaniclastics. The diatreme was formed by explosive volcanic activity, of probably early Tertiary age, subsequent hydrothermal alteration and mineralization took place concurrently within stratigraphic layers in diatreme. Coarse volcaniclastics in the center part of the diatreme, together with complex systems of fracturing, acted as pathways for late hydrothermal fluids which caused alteration of volcanic material to sericite, chlorite and carbonate and precipitated ore minerals, quartz and calcite in the voids. Porosity and permeability were key factors in determining which portions of the layered diatreme were mineralized. The lower part of certain layers retained a relatively high porosity and were extensively mineralized. Metallic mineralization, consisting mostly of pyirte, sphalerite and arsenopyrite, is found as disseminations, tuff-breccia filling and veins.

• Geomechanics and Engineering
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• v.17 no.4
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• pp.343-354
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• 2019

The present study demonstrates the application of seismic petrophysics and amplitude versus angle (AVA) forward modeling to identify the reservoir fluids, discriminate their saturation levels and natural gas composition. Two case studies of the Lumshiwal Formation (mainly sandstone) of the Lower Cretaceous age have been studied from the Kohat Sub-basin and the Middle Indus Basin of Pakistan. The conventional angle-dependent reflection amplitudes such as P converted P ($R_{PP}$) and S ($R_{PS}$), S converted S ($R_{SS}$) and P ($R_{SP}$) and newly developed AVA attributes (${\Delta}R_{PP}$, ${\Delta}R_{PS}$, ${\Delta}R_{SS}$ and ${\Delta}R_{SP}$) are analyzed at different gas saturation levels in the reservoir rock. These attributes are generated by taking the differences between the water wet reflection coefficient and the reflection coefficient at unknown gas saturation. Intercept (A) and gradient (B) attributes are also computed and cross-plotted at different gas compositions and gas/water scenarios to define the AVO class of reservoir sands. The numerical simulation reveals that ${\Delta}R_{PP}$, ${\Delta}R_{PS}$, ${\Delta}R_{SS}$ and ${\Delta}R_{SP}$ are good indicators and able to distinguish low and high gas saturation with a high level of confidence as compared to conventional reflection amplitudes such as P-P, P-S, S-S and S-P. In A-B cross-plots, the gas lines move towards the fluid (wet) lines as the proportion of heavier gases increase in the Lumshiwal Sands. Because of the upper contacts with different sedimentary rocks (Shale/Limestone) in both wells, the same reservoir sand exhibits different response similar to AVO classes like class I and class IV. This study will help to analyze gas sands by using amplitude based attributes as direct gas indicators in further gas drilling wells in clastic successions.

• Economic and Environmental Geology
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• v.48 no.2
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• pp.103-114
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• 2015

Jinsan gold deposit is a hydrothermal vein type deposit consisting of several fissure filling quartz veins developed within the Changri Formation of the Ogcheon Supergroup in Geumsan, Chungnam. This study is to provide an efficient exploration and development strategies based on the characteristics of the geology, geological structure, core logging, and ore vein occurrence and grade for the four pits (New pit, Main pit, Yanghapan pit and Teugho pit). Quartz veins are mostly developed with the strike of $N10^{\circ}-25^{\circ}W$ and $N5^{\circ}-20^{\circ}E$, and the thickness is in the range of 0.1~0.5 m, sometimes extending to over 1m. Although the quartz veins commonly form massive shape, they sometimes show zonal structure, comb structure as well as brecciated texture. Major ore minerals are pyrite and chalcopyrite, and pyrrhotite, sphalerite, galena, marcasite, electrum and chalcocite are also accompanied as minor phases. Gray and milky white quartz veins, which are occasionally crosscut by calcite vein, also include fluorite. Ore evaluations for the 22 samples revealed that the samples from the pits generally have very low Au contents, lower than 1 g/t, but some clay samples of drilled core show very high Au concentrations, up to 141 g/t, indicating that Au content is much higher within fault gouges rather than within fresh quartz veins. This may represent that gold might have been reworked and reprecipitated by hydrothermal fluids in association with reactivation of the faults, and thus suggest that ore occurrence in this deposit is very complex and irregular and therefore more precise and systematic exploration is required.