• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.499-505
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• 2001

The objective of the paper was to measure the pressure drop and to investigate the recirculation region of the conical orifices used in Kwang-yang Iron & Steel Company. The flow field with water used as a working fluid was the turbulent flow for Reynolds number of $2{\times}10^4$. The effective parameters for the pressure drop and the recirculation region were the conical orifice's inclined angle (${\theta}$) against the wall, the interval(L) between orifices, the relative angle of rotation(${\alpha}$) of the orifices, the shape of the orifice's hole(circle, rectangle, triangle) having the same area. It was found that the shape of the orifice's hole affected the pressure drop and the flow field a lot, But the other parameters did not make much differences to the pressure drop. The PISO algorithm with FLUENT code was employed.

• 대한기계학회논문집B
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• 제29권10호
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• pp.1075-1082
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• 2005

The characteristics of longitudinal dispersion enhancement by the flow oscillation are numerically studied according to various groove geometries in a 2-D channel in the present study. The length of expanded section l$_{1}$/h$_{1}$ is varied from 0 to 8.75. The oscillating flow condition is given at both side ends, i.e., u = Asin ($2{\pi}ft$) The non-dimensional temperatures at both side ends are set to zero. The bottom and top walls are adiabatic. The local heat sources are located at the middle of the groove wall. In order to solve the governing equations, the SIMPIER algorithm is employed. The present results indicate that maximum longitudinal thermal dispersion can be achieved when the area ratio of the expanded section to the contracted section in the grooved channel becomes 1.

• 한국기계가공학회지
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• 제10권4호
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• pp.115-120
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• 2011

A ribbed tube consumes more power to transport the fluid by comparing with flat one. After the tangential velocity component occurs, its contact area with the ribbed tube becomes large and it enables the effective energy transportation. The flow characteristics vary according to the geometry of tube rib. This study aims to investigate the flow characteristics of fluids working at Reynolds numbers of 20,000, 40,000, 60,000 and 80,000 with the air at $15^{\circ}C$ in the ribbed test tube high 1mm and wide 8.48mm. As the flow characteristics are included with the states of fully developed hydrodynamical region, axial velocity vector distribution and non-dimensional velocity distribution, they are shown with the physical validity.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 추계학술대회 논문집
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• pp.44-47
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• 2004

Vortexing might occur during draining from tanks which reduces the rate of outflow. This phenomenon has practical relevance in the fuel feed system in space vehicles and rockets. Due to environmental disturbances rotational motion can be generated in the liquid-propellant tank, which in turn can affect the rate of outflow to the engines. The phenomenon is initialized by rotating the fluid In the experimental tank. The dip quickly develops into a vortex with an air core, which extends to the bottom port, reducing the effective cross-sectional area of the drain outlet and consequently the flow rate. Flow characteristics are investigated using SPIV(Stereoscopic Particle Image Velocimetry) method.

• 동력기계공학회지
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• 제12권6호
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• pp.64-69
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• 2008

The spatial fuel distribution of the stratified charge of a high pressure 6-hole injector was examined in a single cylinder optical direct injection spark ignition(DISI) engine. The effects of in-cylinder charge motion, and fuel injection pressure, and coolant temperature were investigated using a planar LIF(Laser Induced Fluorescence) technique. It was confirmed that the in-cylinder tumble flow played more effective role in the spatial fuel distribution of the stratified charge than the swirl flow during the compression stroke and the fuel distribution area increased due to the activation of the fuel vaporization by the increase of the coolant temperature. But, the increase of the fuel supplying pressure could not change the pattern of the fuel vapor distribution against the expectation.

• International Journal of Aerospace System Engineering
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• 제10권1호
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• pp.1-13
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• 2023

The present study was attempted to investigate flow interference effects and the aerodynamic characteristics of the front and rear wings of a joined-wing aircraft by changing the configuration variables. The study was performed using a computational fluid dynamics(CFD) tool to demonstrate forward flight and analyze aerodynamic characteristics. A total of 9 configurations were analyzed with variations on the position, height, dihedral angle, incidence angle, twist angle, sweepback angle, and wing area ratio of the front and rear wings while the fuselage was fixed. The quantities of aerodynamic coefficients were confirmed in accordance with joined-wing configurations. The closer the front and rear wings were located, the greater the flow interference effects tended. Interestingly, the rear wing did not any configuration change, the lift coefficient of the rear wing was decreased when adjusted to increase the incidence angle of the front wing. The phenomenon was appeared due to an effective angle of attack alteration of the rear wing resulting from the flow interference by the front wing configurations.

• Spatial Information Research
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• 제17권2호
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• pp.223-239
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• 2009

우리나라 중소규모의 대부분 하천의 경우 유량 자료의 부족 또는 미계측 지역으로 인하여 효율적인 저수유량 산정이 어려운 실정이다. 따라서 본 연구의 목적은 수계별 환경용량을 고려한 허용부하량 산정을 위해 면적함수 관계식을 이용한 저수유량의 산정방안을 제시하는 것이다. 이를 위해 남한강 상류 지역의 유역면적 $606km^2$인 주천강 유역과 미계측 유역면적 $4,551km^2$인 옥동천 합류 후인 한강 유역을 시험하천으로 선정하였다. 적용결과, 주천 하류부의 저수 유량은 $1.9m^3/s$로, 미계측 유역인 옥동천과 한강의 합류 후의 저수유량은 $20.7m^3/s$로 계산되었다. 이를 영월군에서 고려하고 있는 BOD목표치 1.0-1.2mg/l로 계획하면 허용부하량은 각각 164-197kg/day 및 1,788-2,146kg/day로 추정되었다. 본 연구에서 제시한 허용부하량 산정방법은 자료가 충분하지 않은 유역이나 미계측 유역에 대해 유용하게 이용될 것으로 기대한다.

• 수산해양교육연구
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• 제6권1호
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• pp.58-76
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• 1994

Heat transfer and pressure drop measurements are made on low integral-fin tubes in turbulent water flow condition. The integral-fin tubes investigated in this paper are nominally 19mm in diameter. Eight tubes have been used with trapezoidally shaped integral-fins having fin density from 748 to 1654 fpm and 10, 30 grooves. Plain tube having same diameter as finned tube is also tested for comparison. Experiments are carried out using R-11 as working fluid. The refrigerant condensates at a saturation state of $30^{\circ}C$ on the outside tube surface cooled by coolant. The amount of noncondensable gases present in the test loop is reduced to a negligible value by repeated purging. For a given heat input to the boiler and given cooling water flow rate, all test data are taken on steady state. The heat transfer loop is used for testing single long tubes and cooling water is pumped from a storage tank through filters and flowmeters to the horizontal test section where it is heated by steam condensing on the outside of the tube. The pressure drop across the test section is measured by means of pressure gauge and manometer. Each tube tested is cleaned with sodium dichromate pickling solution and well rinsed with water prior to installation in the test section. The results obtained in this study is as follows : 1. Based on inside diameter and nominal inside area, heat transfer of finned tube is enhanced up to 4 times as that of a plain tube at constant Reynolds number and up to 2 times at constant pumping power. 2. Friction factors are up to 1.6~2.1 times those of plain tube. 3. At a given Reynolds number, Nusselt number decrease with increasing pitch to diameter. 4. The constant pumping power ratio for low integral-fin tubes increase directly with the effective area to the nominal area ratio, and with the effective area diameter ratio.

• 한국융합학회논문지
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• 제5권4호
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• pp.75-79
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• 2014

본 연구에서는 자동차 냉각팬에 대해서 유동해석을 수행하였다. 냉각팬의 형상에 대하여 유동 조건은 같게 하여 Canival, Teracan 및 basic 3가지의 모델을 CATIA프로그램으로 설계하여 본 해석을 실시하였다. 날개의 모양에 따라 유체의 속도의 등고선이 변화하는 것을 볼 수 있으며, 날개의 모양 또는 넓이에 따라 각기 다른 압력분포를 볼 수 있었다. 세 가지 모델 중, Teracan 모델인 냉각팬이 공기의 유동이 많아 라디에이터의 열을 식히는데 가장 효율적이 된다고 사료된다. 그리고 디자인 면에서의 융합 기술로의 접목도 가능하여 미적인 감각을 나타낼 수 있다.

• Membrane and Water Treatment
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• 제10권1호
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• pp.75-82
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• 2019

In a highly urbanized area, land availability is limited for the installation of space consuming stormwater systems for best management practices (BMPs), leading to the consideration of underground stormwater treatment devices connected to the stormwater pipe system. The configuration of a stormwater pipe network determines the hydrological and pollutant transport characteristics of the stormwater discharged through the pipe network, and thus should be an important design consideration for effective management of stormwater quantity and quality. This article presents a multi-objective optimization approach for designing a stormwater pipe network with on-line stormwater treatment devices to achieve an optimal trade-off between the total installation cost and the annual removal efficiency of total suspended solids (TSS). The Non-dominated Sorted Genetic Algorithm-II (NSGA-II) was adapted to solve the multi-objective optimization problem. The study site used to demonstrate the developed approach was a commercial area that has an existing pipe network with eight outfalls into an adjacent stream in Yongin City, South Korea. The stormwater management model (SWMM) was calibrated based on the data obtained from a subcatchment within the study area and was further used to simulate the flow rates and TSS discharge rates through a given pipe network for the entire study area. In the simulation, an underground stormwater treatment device was assumed to be installed at each outfall and sized proportional to the average flow rate at the outfall. The total installation cost for the pipes and underground devices was estimated based on empirical formulas using the flow rates and TSS discharge rates simulated by the SWMM. In the demonstration example, the installation cost could be reduced by up to 9% while the annual TSS removal efficiency could be increased by 4% compared to the original pipe network configuration. The annual TSS removal efficiency was relatively insensitive to the total installation cost in the Pareto-optimal solutions of the pipe network design. The results suggested that the installation cost of the pipes and stormwater treatment devices can be substantially reduced without significantly compromising the pollutant removal efficiency when the pipe network is optimally designed.