• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.179-190
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• 2006

The water supply tunnel has different characteristics which play a important role in stable water supply to the public from mechanical behavior and maintenance in comparison with road md railway tunnel. In this study, the present state and characteristics of water supply tunnels controlled by K-water have been investigated. The distribution of effective stresses that takes into account the effect of seepage forces induced by internal water pressure are estimated from closed-form and numerical method. The analysis of stress-strain behavior, seepage problem and hydrojacking for ensuring safety of existing water supply tunnel against neighboring new construction has been conducted.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1-5
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• 2007

A majority of piping vibration problems are induced by internal fluid pulsation; turbulent flow, vortex shedding at internal discontinuities, and pressure pulsation at equipment nozzles. The pulsation at the pressure sources resonates acoustically with the piping and the amplified pressure pulsation can generate shell mode vibration in the piping. Reheater attemperator piping supplies water from feedwater pump to reheater attemperator to control the boiler temperature. In normal operating condition, the high frequency shell mode vibration occurred in the piping with the high level of sound(105 ${\sim}$ 117 dB). The vibration sources are pressure pulsation in the pump nozzle and the frequencies are related to the blade passing frequencies. The objects of this paper are to analyze the cause of the high frequency vibration and to establish corrective actions.

• The KSFM Journal of Fluid Machinery
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• v.4 no.3 s.12
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• pp.39-45
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• 2001

It is reported recently that the pump head deterioration near the best efficiency point, from single-phase flow to the choke due to air entrainment became less in a screw-type centrifugal pump than in a general centrifugal pump. Moreover, at a narrow tip clearance, the pump head became partially higher in two-phase flow than that in single-phase flow. However, the internal pressure fluctuations on this pump due to air entrainment have not been studied yet. For that reason, we have examined the influences of void fraction, flow coefficient and impeller tip clearance on pressure fluctuations in the casing. The void fraction became larger, the influence of tip clearance on pressure distribution became less.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.1
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• pp.68-77
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• 1995

The two-dimensional pressure distribution, which is the most important parameter in the casting cleaning installations(CCI), was analyzed using the K-FIX computer program for two-phase flow. Modelling was done using R-Z coordinates for the initial and boundary conditions which don't have periodic influx and efflux, and also there was the electric discharge due to high pressure and temperature. The marked particles were introduced to prodict the structure and the size of main and local moving surfaces. The initial and boundary conditions were modified due to the internal structure of CCI.From the results of numerical analysis, it was shown that the maximum pressure on casting was increased with the increase of a water level. The pressure on casting in the radial direction was higher than that in axial direction. Also, it was proved that by introducing the marked particles it was possible to predict the surface structure in case of two-phase flow.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.3
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• pp.90-99
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• 1994

To investigate the undrained shear strength characteristics of marine soils with high water content, high compressibility and weak bearing capacity, a series of undrained triaxial tests with pore pressure measurements on undisturbed and disturbed Banwol marine clay in normally consolidated and overconsolidated states is carried out. The results and main conclusions of this study are summarized as follows : 1 . When the consolidation pressure is increased, the maximum deviator stress of disturbed and undistubed clay in normally consolidated state is increased. Pore pressure parameters and internal friction angle of undisturbed clay are greater than those of disturbed clay. 2. The relationship between pore pressure and axial strain of undisturbed clay in normally consolidated state can be expressed as a hyperbolic function like stress-strain relation proposed by Kondner. 3. In the pore pressure-axial strain relation of disturbed clay in normally consolidated state, failure ratio R'f is greatly deviated in the range of 0.7~0.9 proposed by Christian and Desai. 4. For overconsolided clay, when overconsolidation ratio (OCR) is increased, normalized maximum deviator stress is increased and maximum pore pressure is decreased gradually. 5. Cohesion of overconsolidated clay is greater than that of nomally consolidated clay and internal friction angle slightly is decreased. 6. Pore pressure parameter at failure (Af) of overconsolidated clay is varied with OCR, Af becomes negative values with increment in OCR

• Journal of Power System Engineering
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• v.4 no.1
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• pp.26-32
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• 2000

Single-phase heat transfer performance and pressure drop for internally grooved tubes with angles were studied. Experiments were carried out in a counter flow heat exchanger with water as a working fluid. Two commercially available internally grooved tubes and smooth tube were tested. The internal diameter of the smooth tube was 16.5mm and the internal diameters of grooved tubes were 15.4mm, 14.9mm, 15.0mm, 16.7mm, respectively. Grooved angles in the tubes were $37^{\circ},\;43^{\circ},\;45^{\circ},\;50^{\circ}$, respectively. An experimental device to measure the friction factor and heat transfer coefficient was constructed. The experimental results were obtained for the fully developed turbulent flow of water in tube on the condition of uniform heat flux. As the increase of flow rate, Reynolds number, numbers of groove and grooved angle led to the increase of pressure drop. Also this paper showed that heat transfer rate increased with increasing numbers of groove and grooved angle. An empirical relation taken from this study represented most of the data within ${\pm}25%$.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.199-206
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• 2001

Landslides generally occur due to influences of the internal and external factors. Internal factors include ground characteristics, terrain and so on. External factors can also be divided into natural factors such as rainfall, ground water, earthquake and so on, and artificial factors resulting from cutting and embankments. Among these factors, rainfall becomes the most important external factors by means of which landslides occur in Korea. To appropriately deal with tile effects of pore water pressures due to rainfall, the method using the pore water pressure ratio(r$\_$u/) is generally applied in slope stability analysis or the design of slope reinforcements. Since tire value of r,, is in general not constant over the whole cross section, in most slope stability analyses the average values are used with little loss in accuracy. However, determination of the average values of r$\_$u/ to applied in the design is difficult problem. Therefore, in this study, tile average values of r$\_$u/ according to the intensity of rainfall and slope inclination is suggested based on results of the small scaled model tests using the artificial rainfall apparatus. It is found from the model tests that the average values of r$\_$u/ is about 0.07∼0.18(in case of the intensity of rainfall is 50mm/hr.), about 0.10∼0.28(in case of the intensity of rainfall is 100mm/hr.), and about 0.10∼0.33(in case of the intensity of rainfall is 150mm/hr.).

• Korean Journal of Agricultural Science
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• v.47 no.3
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• pp.485-496
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• 2020

Recent changes in the disaster environment have greatly increased the possibility of internal erosion in deteriorated reservoirs; thus, countermeasure methods are required to enhance the drainage performance of embankments. Sand filters have been mainly used to prevent internal erosion; however, due to the sand depletion and environmental problems, new alternative materials are required to replace the sand in the filter zone. In this study, crushed stone was used instead of sand as a material that could satisfy permeability, material supply, demanding conditions, and economic efficiency. Although crushed stone has excellent drainage performance, it has a clogging phenomenon due to its high permeability. Accordingly, the materials need to be separated with a geotextile wrapping method. Additionally, the 3D numerical analysis and a large model experiment were conducted to evaluate the seepage characteristics and in-site application of the crushed stone filter. As a result, the crushed stone filter showed an excellent dispersion effect by reducing the pore water pressure by about 9.5 times that of the sand filter. In addition, it was shown that the safety factor for piping increased significantly by reducing internal erosion. When comparing the economics and supply and demand conditions of the material, crushed stone was evaluated as an effective method to reduce the internal erosion of embankments at deteriorated reservoirs.

• The KSFM Journal of Fluid Machinery
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• v.11 no.2
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• pp.13-19
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• 2008

Butterfly valves are widely used as control valves for industrial process. For the definition of optimum configuration of the valve, wide range of related studies has been actively conducted in the case of working fluids of water or air under the normal temperature. Recently, internal flow and performance characteristics of cryogenic butterfly valve for LNG carrier take a growing interest in the field of research and development. Therefore, present study is aimed to investigate the internal flow and performance characteristics of the cryogenic butterfly valve because the study result for the valve can be hardly found at present. Part 1 of this paper describes the study result of a butterfly valve model under the condition of the normal temperature. Succeeding Part 2 of this paper will describe the internal flow characteristics of a cryogenic butterfly valve for LNG carrier. The results of Part 1 show that pressure loss coefficients and flow rate coefficients obtained by the present experiment and CFD analysis agree well each other. Moreover, internal flow visualization for the valve by CFD analysis and PIV measurement have revealed complicated flow patterns of the internal flow field in detail.

• Transactions on Electrical and Electronic Materials
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• v.18 no.2
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• pp.66-69
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• 2017

The internal temperature of human-tissue transfers must be steadily maintained regardless of the external environmental changes. An ice pack and dry ice are the coolants for the transfer containers for which heat-insulating materials such as EPP (expended polypeopylene and EPS (expended polystrene) are used; however, changes of the external temperature/pressure and the melting of the coolants that is due to a long carriage result in changes of the internal temperature, and this makes it difficult to maintain the temperature. Accordingly, the thermoelectric element was used to design/manufacture a transfer container to maintain the internal temperature regardless of the external environmental changes. As a result of the measurement of the changes of the internal temperatures of the manufactured thermoelectric-element container and the EPS container over time, the internal temperature of the EPS container was increased, whereas the internal temperature of the thermoelectric-element container was maintained. The temperature of the distilled water that was poured into the containers indicated a pattern identical to that of the internal temperature.