• 한국수자원학회논문집
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• 제42권10호
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• pp.785-793
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• 2009

본 연구에서는 부정류 상태의 조압수조를 해석 할 수 있는 수치모형이 개발되었다. 그리고 부정류 효과를 고려한 파이프의 파괴확률 산정을 위한 신뢰성 모형이 개발되었다. 파이프 파괴의 상대적 위험도 평가와 조압수조의 기능성 평가를 위해 부정류 효과를 고려한 조압수조가 있는 상수관망 시스템의 파괴확률을 산정하였다. 신뢰성 해석을 통하여 부정류가 파괴확률을 크게 증가 시키는 것을 알 수 있었으며 조압수조가 부정류의 압력을 크게 감쇠시킴으로써 파괴확률을 현저히 저하시키는 것을 확인할 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.835-840
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• 2000

The objective of the present study is to investigate the characteristics of pressure wave propagation of viscous fluid flow in a circular pipe line. The goal of this study is to select the best frequency of each control factor of a circular pipe. We intend to approach a formalized mathematical model by a very exact and reasonable polynomial for fluid transmission lines. and we computed this mathematical model by computer. The results show that the oil viscosity decreased as the length of the circular pipe increases. and The energy of pressure wave propagation decreased as the pipe diameter decreases. The factor is that density of oil was changed resonant frequency. It has been found the viscosity characteristics is changed largely by length of hydraulic pipe and volume of cavity tank.

• 태양에너지
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• 제7권2호
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• pp.37-53
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• 1987

This study has been prepared for the purpose of developing the system performance prediction method of natural circulation solar hot water system. The storage tank of the natural circulation solar hot water system equipped with flat-plate solar collector is located at higher elevation than the solar collectors. Therefor, the storage tank temperature distribution formed accordance with configuration of storage tank by flow rate of circulating fluid affect system collection efficiency. In this study measure the storage tank temperature distribution with various experimental system under real sun condition and present the theoretical prediction method of the storage tank temperature. Moreover measure the flow rate not only day-time but also night-time reverse flow rate with die injection visual flow meter. Main conclusion obtain from the present study is as follows; 1) The storage tank temperature distribution above the connecting pipe connection position is the same as that of the fully mixed tank and below the connection position is the same as that of stratified tank. 2) The system performance sensitive to the storage tank temperature distribution. Therefore detailed tank model is necessary. Average storage tank temperature can be calculate 3% and storage tank temperature profile can get less than 10% difference with this model system.

• 연구논문집
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• 통권30호
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• pp.67-77
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• 2000

This study was performed to investigate the characteristics and performance of model Decanter for separating swine wastewater to solid and liquid which is slurry state with 12.6% TS. Swine wastewater of the slurry tank was pumped into model Decanter which capacity was $2m^3$/hr in 10% TS Slurry inside of bowl was separated to solid-liquid by centrifugal acceleration. Sampling was done in the section of slurry feed pipe, supernatant outflow pipe, cake discharge pipe. After solid-liquid separation TS, $COD_cr$ and slurry volume reduction effect represented 38%, 40%, 19.6% respectively. Relation factor of model Decanter operation slurry concentration, optimum retention time of slurry, overflow velocity of supernatant, supernatant concentration, sludge removal rate etc. Optimal operation conditions can be set and evaluated efficiency based on the experimental results in the case of Decanter adopted for solid-liquid separation in highly concentrated swine wastewater.

• 한국군사과학기술학회지
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• 제24권2호
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• pp.228-236
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• 2021

In order to understand the underwater noise source factor of the linear pump type forced ejection system, a reduced-model compressed water experiment device was developed. The reduced-model compressed water experiment device consists of a reverberation tank, a linear pump type forced ejection device, and an underwater vehicle. The underwater noise source was selected from the hydraulic ram moving speed, the hydraulic ram/piston pipe spacing, the ejection pipe inlet/water ram area ratio, and the number of water ram inlets. The underwater vehicle was ejected into the reverberation tank by the device. The source level was derived from the measured sound pressure. The source level tends to increase as the hydraulic ram/piston tube spacing and the hydraulic ram moving speed increase. The source level tended to increase as the area ratio was increased, but the level was weak. The number of water ram inlet did not affect the source level.

• 한국자동차공학회논문집
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• 제21권4호
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• pp.23-32
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• 2013

This paper presents the simulation of the multi-cylinder 4-stroke cycle spark-ignition engine using a commercial simulation tool, AVL BOOST. Various models were examined to select the appropriate models that would best serve to analyze the main components of the intake and exhaust systems-the plenum chamber, the muffler and the exhaust manifold branch junction. For the plenum chamber and the muffler, the tank model and the pipe model were tested. In order to analyze the exhaust manifold branch junction, a complicated model which reflects the actual shape and involves pressure drops was compared to a simplified one. The results show that both the tank model and the pipe model are applicable with satisfying accuracies for the plenum chamber and the muffler. However, the tank model is more desirable in regards to convenience in modeling and efficiency in calculation. Though both the complicated model and the simplified model show satisfying accuracies for the exhaust manifold branch junction, the simplified model is recommended in regards to convenience in modeling and efficiency in calculation.

• 한국방재안전학회논문집
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• 제12권4호
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• pp.1-13
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• 2019

최근 기후변화로 인해 강우강도 및 빈도의 증가에 따른 국지성 집중호우의 피해가 증가함에 따라 초기 우수에 대응할 수 있는 시설물 설치가 필요한 실정이다. 이를 위해, 빗물을 직접 유출하지 않고 저류 시키는 저영향 개발(Low Impact Development)기법을 적용한 시설물 설계 및 수치모형을 이용한 유출저감효과 검토에 관한 연구가 많이 진행되어 왔다. 그러나 대부분의 연구는 유출저감효과에 대한 검토만 수행된 반면, 시설물에 유입되는 유량에 의한 흐름특성 변화 검토 및 안정성 검토에 관한 연구는 미비한 실정이다. 이에 본 연구에서는 LID 기법이 많이 적용되고 있는 회전교차로를 대상으로 하여, 회전교차로 내의 우수저류조의 관망시스템의 안정성 검토를 3차원 수치모형인 FLOW-3D를 사용하여 검토하였다. 또한 우수저류조의 최적의 설계방안 도출을 위하여 우수저류조의 수를 증가하여 용량증가에 따른 유속과 동압의 변화를 검토하고 설계기준과 비교하였다. 우수저류조의 제원 및 유입유량은 선행연구에서 제시된 값을 적용하여 수치모의를 수행한 결과, 유속은 저류조 설치개소 수가 증가할수록 빨라지는 것을 확인하였고, 대부분 설계기준 범위 안에 유속이 형성되는 것을 확인하였다. 다만 추가 저류조가 3개 이상일 경우는 추가저류조관에서 유속이 3.44 m/s가 발생하여 설계유속의 허용범위를 초과하였고, 유속의 증가율도 일정해지는 것으로 나타났다. 난류강도 및 바닥전단력 비교의 경우, 저류조 설치 개소수가 증가함에 따라 바닥전단력이 한계소류력보다 크게 나타나 유입토사의 침전은 발생하지 않을 것으로 예상되나 난류강도의 크기가 작아져 플록(Floc)형성으로 인한 토사 침전이 발생할 수 있음을 고려해야한다. 최종적으로 유속을 이용한 동압 산정 결과를 우수관 설계에 일반적으로 사용되는 압력관의 허용내압과 비교하였을 경우, 동압이 허용내압보다 작게 나타났다. 이를 통하여 본 연구에서 제안한 우수저류조 제원으로 설계할 경우 추가 저류조를 2개까지 설치하는 것이 가장 적합한 것으로 나타났다. 이는 저류조를 계속하여 설치하게 되면 배수가 원활해져 관내 유속이 빨라지고, 유속증가로 인하여 관의 마모손상 등의 문제가 일어날 수 있기 때문이다. 그러나 본 연구는 저류조의 제원 및 우수의 유입량을 가정하였고, 단순히 저류조를 추가하여 저류조 설계방안을 도출한 한계점이 있어 향후에는 다양한 저류조 형태 및 우수유입 시나리오를 적용하여 검토한다면 보다 효율적인 설계방안 도출이 가능할 것으로 기대된다.

• 한국컴퓨터정보학회논문지
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• 제17권6호
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• pp.101-109
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• 2012

고 품질의 소프트웨어를 개발하기 위해서는 소프트웨어 내에 잠재된 결점을 제거하기 위한 품질관리계획이 요구된다. 이를 위해 결점 제거 프로필을 적절히 기술해야만 한다. 기존의 유조와 도관 모델은 결점이 제거되고 도피하는 결점을 계산하는데 복잡한 과정을 수행한다. 또한 어느 단계에서 삽입된 결점이 제거되고 도피하였으며, 단계별 결점 발견율이 얼마인지를 상세히 알고 있어야만 한다. 이러한 복잡한 과정을 단순화하기위해 본 논문은 결점필터링 개념에 기반하여 모델을 제시하였다. 제시된 모델은 임의의 단계에서 제거와 도피한 결점이 어느 단계에서 삽입된 결점에 관련되어 있는지 고려할 필요가 없어 결점을 보다 간략히 기술할 수 있는 장점이 있다. 또한, 결점 제거 품질척도와 생산성 척도의 함수에 기반하여 결점제거에 요구되는 노력 추정 모델을 제시하였다.

• 상하수도학회지
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• 제12권2호
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• pp.90-98
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• 1998

The optimal rechlorination in water distribution systems was investigated by incorporating optimization techniques into a numerical water quality model. For a hypothetical system that consists of 10 junctions including a storage tank and 12 links, the bulk ($k_b$) and pipe-wall ($k_w$) decay-rate constants of chlorine residual are assumed to be 2.0 1/day and 1.5 m/day, respectively. It was also assumed that the lower and upper limits of chlorine residual in the network are 0.2 mg/L and 0.6 mg/L. When the chlorine source is only the storage tank (without rechlorination), the high levels of chlorine residual appear near the storage tank to maintain the chlorine residuals above the lower limit over the junctions. On the other hand, the chlorine residuals in the network are distribute within the desirable range (0.2 - 0.6 mg/L) after the optimal rechlorination through five injection sites including the storage tank. In case of a real water distribution system that comprises 28 junctions including a clear well and 27 links, the bulk and pipe-wall decay-rate constants are 0.3 1/day and 0.2 m/day, respectively. Before rechlorination, the required chlorine residual at the clearwell is 5.1 mg/L to keep the chlorine residuals above the minimum level (0.6 mg/L) over the junctions. By the optimal rechlorination at five injection sites, the chlorine residuals are distributed within a desirable range of 0.6 mg/L through 2.0 mg/L, which can avoid the excess of chlorine residuals near the clear well. Consequently, total chlirine doses are decreased by 81% in the hypothetical distribution network and 69 % in the real distribution network for satisfying the minimum chlorine residuals.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.732-736
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• 2008

The traditional method to calculate the gravity feed is to assume that only one tank in fuel system supplies the needed fuel to the engine, and then calculated for the single branch. Actually, all fuel tanks compete for supplying oil. Our method takes into consideration all fuel tanks and therefore, we believe, our method is intrinsically superior to traditional methods and is closer to understanding the real seriousness of the oil supply situation. Firstly, the thesis gives the mathematical model for fuel flow pipe, pump, check valve and the simulation model for fuel tank. On the basis of flow network theory and time difference method, we established a new calculation method for gravity feed oil of aeroplane fuel system, secondly. This model can solve the multiple-branch and transient process simulation of gravity feed oil. Finally, we give a numerical example for a certain type of aircraft, achieved the variations of oil level and flow mass per second of each oil tanks. In addition, we also obtained the variations of the oil pressure of the engine inlet, and predicted the maximum time that the aeroplane could fly safely under gravity feed. These variations show that our proposed method of calculations is satisfactory.