• 대한기계학회논문집
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• 제17권9호
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• pp.2381-2389
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• 1993

In this paper the design and test results of a dynamic flow rate sensor was reported. This sensor comprises an 2-way cartridge valve as standard hydraulic component and a displacement sensor. Its working principle bases on the linear relationship between the flow rate and the piston displacement of 2-way cartridge valves under constant pressure drop. This principle is well known, however it is not easy to develop a flow rate sensor with the measurement range of 300 1/min, pressure loss of less than 8 bar at 300 1/min, maximum linearity error of less than $\pm$1% and the maximum rising time of 10 ms. This paper describes the design procedure of the flow rate sensor, the improvement procedure of static performance and test method and results of dynamic performance.

• 지질공학
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• 제28권3호
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• pp.341-348
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• 2018

Landslides can be caused by localized intense rainfall. The loss of human lives and damage to property from landslides is increasing. However, little information exists on the movement and flow of sediment material at the time of rapid landslides. In this study, a field survey was conducted of landslides that occurred in 2013 in the Hadari area of Yeoju city in Korea. This was followed by numerical analysis. The purpose is to analyze the characteristics of a consequent debris flow and its movement at the time of failure. The results of the field survey and numerical analysis are consistent with each other. The maximum velocity of the debris flow was ~9.335 m/s and the maximum sediment thickness ~4.674 m. The latter is similar to the traces of debris flow observed in the field.

• 대한전기학회논문지
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• 제43권4호
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• pp.594-600
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• 1994

The maximum charge accumulation in transformers caused by streaming electrification is commonly observed on the bottom area of transformer winding(i.e.the oil inlet of transformer winding). It is because turbulent flows occur in this portion of transformers. Consequently, if we are to reduce the maximum charge accumulation of transformers, it is important that we should have a good understanding of the conditions of the occurence of partial turbulent flows in the oil inlet of transformer winding. With this point in mind, a simple flow model was designed in this study in order to simulate oil flow in the insulation ducts of power transformers. As a method for mitigating charge accummulation, attention was given to (a) a flow path design for the improvement of flow conditions, and (b) the charge tendency of the material used this design. The results of this study show that the above method is useful for mitigating charge accumulation.

• 한국기계가공학회지
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• 제9권1호
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• pp.55-60
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• 2010

The air resistance about automotive body is studied by the flow analysis in this study. Maximum air flow velocity is shown with 28 to 30 m/s on the upper roof of automotive body. The air flow becomes most regular at automotive body model 3 but the model of 2 or 3 becomes irregular in comparison with the model 1. The maximum air resistance pressure is shown with 413 to 420 Pa at the front bumper of automotive body. The flow velocity at inlet or middle plane of automotive body is shown as the contour same with the model of 1, 2, or 3. But the velocity at outlet plane at model 1 is shown as the contour different with the model of 2 or 3.

• 산업경영시스템학회지
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• 제5권6호
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• pp.41-48
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• 1982

This paper analyzed md developed flow - shop sequencing heuristic method. The essence of the heuristic approach is in the application of selective routine that reduce the size of a problem. The advantages of this approach are consistency. Speed, endurance and the ability to cope with more data and larger systems than is humanly possible, In recent years many heuristic procedures have been suggested for the flow - shop sequencing problem. Although limited comparisons of these procedures have been made, a full scale test and evaluation have not been reported previously. The maximum flow - time criterion is selected as the evaluation criterion is selected as the evaluation criterion of flow - shop's efficiency. The author evaluated these 3 heuristic method's performance. By the evaluation of the result, we can see that the modified methods produce a shorter maximum flow - time than the original methods.

• 설비공학논문집
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• 제18권5호
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• pp.410-417
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• 2006

The present study predicted the effect of the flow rate of coolant on the absorption performance of a vertical falling film type absorber Heat and mass transfer peformances were numerically investigated. The exit temperatures of solution and coolant were decreased as the flow rate of the coolant was increased at the film Reynolds number of 100. The absorption mass flux was increased and then decreased as the distance from the inlet of the absorber was increased. The distance showing the maximum absorption mass flux was ranged from 0.3 to 0.5m. The heat flux and the absorption mass flux were increased and then slowly decreased as the flow rate of the coolant was increased. The maximum values were obtained at the flow rate of coolant of 2.0L/min.

• 지질공학
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• 제27권1호
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• pp.59-66
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• 2017

최근들어 발생하는 강우는 지금까지의 강우특성과 비교하여 여름철에 단기간 집중적으로 내리는 형태로 바뀌고 있다. 2011년 강원도 춘천지역에서는 이러한 집중강우로 인해 많은 산사태가 발생하였으며, 이로 인해 재산피해와 인명피해를 야기시켰다. 본 연구의 목적은 강우에 의한 산사태 물질의 이동에 대한 특성을 분석하기 위해서 현장 자료와 수치해석 자료를 활용하여 시간에 따른 특성의 변화 및 강우량에 따른 특성의 변화를 분석하는 것이다. 본 연구에서는 항복응력 값의 변화를 통해서 강우량을 재현하였으며, 이를 통해서 어떠한 거동 특성을 보이는지 해석하였다. 그 결과 많은 강우에 의해 항복응력 값이 낮아지는 경우가 빠른 속도의 이동형태를 보이고 동시에 넓은 지역에 걸쳐 확산되는 특성을 확인하였으며, 이러한 결과는 현장에서 확인된 토석류의 흔적과 매우 유사하다는 것을 확인하였다. 본 연구를 통해서 산사태 발생 당시의 토석류 최대 속도 및 최대 두께 등을 파악하는 것이 가능하다.

• 한국유체기계학회 논문집
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• 제5권4호
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• pp.54-60
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• 2002

Experimental study was conducted to obtain the air velocity profiles in turbulent pipe flow. The acrylic smooth pipe (${\phi}=80mm$) was used for the test section of the flow loop. It was known that the velocity profiles of turbulent flow were different with Reynolds numbers and the viscous sublayer was usually quite thin. The following conclusions were drawn from the experimental investigations. Maximum velocity of the pipe center and flow-rate are useful for the duct design on the spot. The velocity profiles of high Reynolds number was flatter than those of low Reynolds number. It was known that the exponent, n, for power-law velocity profiles was $6{\sim}9$ depending on Reynolds number ranging from $10^4$ to $10^5$ in the turbulent flow, However, in this experiment study, it was $9{\sim}14$ depending on Reynolds number ranging from 17,000 to 123,727 in the turbulent flow, and $1.7{\sim}3.5$ depending on Reynolds number ranging from 2,442 to 4,564 in the transition region.

• 생태와환경
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• 제45권2호
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• pp.200-209
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• 2012

The current of the water body is very important information for the water quality management on reservoirs. It is applied to hydraulics and water quality model for simulation. In this regard, the current characteristic of water body is the basic information that can be used to predict various conditions. However, it is very slow flowing and is affected by the reservoir operations and external factors. As such, an accurate measurement of the current is a difficult problem. In order to measure the water current, we constructed a drifter. According to the result of flow survey at Yongdam reservoir, 5m and 10 m depth layer flow was investigated from the upstream to the downstream, during a flood period. Maximum flow rate of 5 m depth is 13.8 cm $sec^{-1}$ and 10 m depth shows 4 cm $sec^{-1}$, respectively. But 2m depth shows a backward flow and maximum flow rate is 4 cm $sec^{-1}$. Density currents flow plays the role of back flow in reservoirs. Flow velocity in the reservoir was measured in the range of 1~2 cm $sec^{-1}$, at normal flow season, and the flow direction were different for each survey. This phenomenon occurs because the reservoir volume is very large, compared to the inflow and outflow volume.

• 한국안전학회지
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• 제30권6호
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• pp.63-69
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• 2015

In this study, a 2D hydrodynamic model equipped with critical dry depth scheme was developed to reproduce the flow over staircase. The channel geometry of hydraulic experiment conducted by Ishigaki et al. was generated in the computational space, and the developed model was validated against flow properties such as discharge, velocity and momentum. In addition, the water surface profile and the velocity distribution evolved in flow over two layers staircases were analyzed. When the initial water depth at the upper floor was 0.3 m, the maximum velocity at lower floor was 4.2 m/s, and the maximum momentum was $1.2m^3/s^2$, and its conversion to force per unit width was 1.2 kN/m. This value was equivalent to the hydrostatic force with 50 cm water depth, and evacuation became difficult, as proposed by Ishigaki et al. For the flow over staircases connecting two layers, the maximum run-up height in flat part connecting two layers was approximately two times higher than the initial water depth in upper floor, and the rapid shock wave with sharp front and long tail was propagated.