• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.161-161
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• 2011

The design methodology of the sluice caisson structure is one of important factor that is closely related to the efficiency in tidal power generation. When the sluice caisson is designed to maximize the water discharge capability, it is possible to minimize the number of sluice caissons for attaining the water amount required for achieving the target power generation, which results in reduction of the construction cost for the sluice caisson structure. The discharge capability of sluice caisson is dependent on the geometrical conditions of an apron structure which is placed in both sides of the sluice caisson. In this study, we investigated numerically the variation of water discharge capability of sluice caisson according to the geometrical conditions of apron. Flow fields are simulated with FLOW-3D software using VOF method.

• 전기의세계
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• 제21권4호
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• pp.27-38
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• 1972

This paper discusses the characteristics about the ignition of D.C. main discharge is a plasma jet generator, manufactured for trial as non-transferred type, when the electrical energy appropriate to the ignition is supplied to the gap between the electrodes by using advance discharge of attenuating high frequency voltage generated by a high frequency oscillator with mercury spark gap. These characteristics are under the influences of (a) the length of mercury gap in high frequency oscillator and the quantity of hydrogen flow supplied to it, (b) the condenser capacity of the high frequency oscillator circuit, (c) the length of plasma jet torch in D.C. main discharge circuit and the quantity of argon flow supplied to it, (d) the circuit constants of D.C. main discharge circuit. The results for these characteristics, obtained by this research, are considered to be helpful to the designs for the ignition of a plasma jet as well as the welding arc stabilizer by high frequency discharge and the high frequency arc welder.

• Water Engineering Research
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• 제5권4호
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• pp.195-206
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• 2004

This paper deals with oxygen transfer by air entrainment and energy dissipations by flow characteristics at the stepped drop structure. Nappe flow occurred at low flow rates and for relatively large step height. Dominant flow features included an air pocket, a free-falling nappe impact and a subsequent hydraulic jump on the downstream step. Most energy was dissipated by nappe impact and in the downstream hydraulic jump. Skimming flow occurred at larger flow rates with formation of recirculating vortices between the main flow and the step comers. Oxygen transfer was found to be proportional to the flow velocity, the flow discharge, and the Froude number. It was more related to the flow discharge than to the Froude number. Energy dissipations in both cases of nappe flow and skimming flow were proportional to the step height and were inversely proportional to the overflow depth, and were not proportional to the step slope. The stepped drop structure was found to be efficient for water treatment associated with substantial air entrainment and for energy dissipation.

• 약학회지
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• 제37권1호
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• pp.76-83
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• 1993

The changes in discharge current, emission and/or oscillation frequency of the electric oscillation of a glow discharge are the potential sensitive measure of the concentration of an impurity in the argon plasma supporting gas. A single jet enhanced glow discharge has been interfaced with the gas chromatograph via 1/8" O.D. tube with a heating pad to study the changes in discharge current. To investigate the optimum operating conditions of the glow discharge system as detector for gas chromatography, pressure, gas flow rate, discharge current, distance between the anode and the cathode have been studied.

• 한국제4기학회지
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• 제17권2호
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• pp.79-84
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• 2003

This study revealed the differences in runoff processes of granite drainage basins in Korea and Mongolia by hydrological measurements in the field. The experimental drainage basins are chosen in Korea (K-basin) and Mongolia (M-basin). Occurrence of intermittent flow in K-basin possibly implies that very quick discharge dominates. The very high runoff coefficient implies that most of effective rainfall quickly discharge by throughflow or pipeflow. The Hortonian overlandflow is thought to almost not occur because of high infiltration capacity originated by coarse grain sized soils of K- basin. Very little baseflow and high runoff coefficient also suggest that rainfall almost does not infiltrate into bedrocks in K-basin. Flood runoff coefficient in M-basin shows less than 1 %. This means that most of rainfall infiltrates or evaporates in M-basin. Runoff characteristics of constant and gradually increasing discharge imply that most of rainfall infiltrates into joint planes of bedrock and flow out from spring very slowly. The hydrograph peaks are sharp and their recession limbs steep. Very short time flood with less than 1-hour lag time in M-basin means that overland flow occurs only associating with rainfall intensity of more than 10 mm/hr. When peak lag time shows less than 1 hour for the size of drainage area of 1 to 10 km2, Hortonian overland flow causes peak discharge (Jones, 1997). The results of electric conductivity suggest that residence time in soils or weathered mantles of M-basin is longer than that of K-basin. Qucik discharge caused by throughflow and pipeflow occurs dominantly in K-basin, whereas baseflow more dominantly occur than quick discharge in M-basin. Quick discharge caused by Hortonian overlandflow only associating with rainfall intensity of more than 10 mm/hr in M-basin.

• 분석과학
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• 제8권1호
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• pp.69-77
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• 1995

원자흡수용 gas-jet assisted RF 글로우 방전시스템을 제작하고 시료손실량과 원자흡광도에 미치는 실험변수들에 관한 연구를 수행하였다. 시료손실량과 흡광도는 방전전력, 압력 및 가스흐름에 큰 영향을 받았다. 원자흡광도와 시료손실량을 가스흐름이 600ml/min로 증가할 때 까지 계속 증가하였으며, 방전 압력은 3mbar에서 최대 흡광도를 나타내었다. 방전전력이 증가할수록 시료손실량과 흡광도는 증가하였으나 시스템의 안정도에 영향을 미치는 관계로 적당한 값의 선택이 필요하였다. 스테인리스 스틸 시료 중의 Ni과 황동시료 중의 Cr의 검량선을 작성한 결과 양호한 직선성이 얻어졌다.

• 한국환경과학회지
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• 제23권4호
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• pp.561-569
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• 2014

The water resources system of Jeju-do Island entirely depends on groundwater. This study is making a precision observation of baseflow, surface water, water shortage that might be vulnerable to climate change and drought in future. The field observation of baseflow discharges in Akgeuncheon stream has regularly been made with ADCP and ADC and Flowmate every two weeks for twenty-two (22) months (July 8, 2011 to April 27, 2013). This paper represent the results of calculating discharge of a number of hydraulic structures (broad-crested weirs) with comparing and has been calculated more accurate discharges with suitability of different observation methods. The average discharge has been observed 0.851 $m^3/s$, whereas the average ADC and Flowmate is 0.709 $m^3/s$. Meanwhile, stream discharge has been calculated 0.709 $m^3/s$ through the broad-crested weir equation. The discharge has calculated with the weir equation greatly changed according to even a small change in the water level. However, it showed a similar trend to one of the observed discharge. Although, in past there were generating errors caused by observers' strides, vertical and horizontal flow velocity distribution when the average flow velocity had been measured, non-prismatic flow, turbulent flow and others in ADC. This study comes up with the weir equation is more suitable for the characteristics of Jeju-do could be presented through an observations of baseflow discharge.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.561-566
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• 2008

The reciprocating compressor is widely used in the industry field, because it has simple principle and high efficiency. In this work, in order to improve design of discharge passage line in hydrogen compression system Numerical analysis was conducted. General information about an internal gas flow is presented by numerical analysis approach. Relating with hydrogen compressing system, which have an important role in hydrogen energy utilization, this should be a useful tool to observe the flow quickly and clearly. Flow characteristic analysis, including velocity, pressure and turbulence kinetic energy distribution of hydrogen gas going out from the cylinder to discharge-path line are presented in this paper. Discharge-passage model is designed based on real model of hydrogen compressor. Pressure boundary conditions are applied considering the real condition of operating system. The result shows velocity, pressure and turbulent kinetic energy are not distributed uniformly along the passage of the Hydrogen system. Path line or particles tracks help to demonstrate flow characteristics inside the passage. The existence of vortices and flow direction can be precisely predicted. Based on this result, the design improvement might be done.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2000년도 춘계학술대회논문집
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• pp.91-98
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• 2000

Derivation of stage-discharge relationship and characteristics for Yangsan river is presented in this paper. This research has been conducted as the second one after the first trial of 1997. The determination of discharge at a Yangsan river gauging was best made by measuring the flow velocities with a current meter and rod float. The rating curve obtained through 52 stage-discharge measurements on Yangsan river basin in 1999 is represented by Q=15.3540-140.6076H+182.44372$H^2$, which is discovered to be most excellent among other curves in reliability analysis. The capability of the observed stage-discharge data for Yangsan river was tested by HEC-RAS program, and its capability to reproduce discharge was investigated and compared with the computational results. Rating curve stability is determined on the basis of deviations in the stage-discharge relationship, utilization of specific gauge, and absolute differences between sequential stream flow measurements and an analysis residuals. Therefore it seems necessary to research method to obtain rating curve in a rigorous and accurate manner.

• 한국분무공학회지
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• 제27권3호
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• pp.144-154
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• 2022

Gas injection is a technique applied to improve throttling in liquid rocket engines and atomization in effervescent injectors. When a gas is injected into a liquid, it creates a two-phase flow inside the injector. The changes (bubbly flow, slug flow, annular flow, etc.) in the two-phase flow affect the injector's spray characteristics. In this study, cold-flow tests were performed by using three injectors with different orifice diameters and four aerators with different gas injection hole diameters. The experiments were done by changing the thrust ratio (liquid mass flow rate ratio) and gas-liquid mass flow rate ratio. Two-phase flow transition, breakup length, and discharge coefficient according to the injector/aerator design and flow conditions were investigated in detail.