• 한국지하수토양환경학회지:지하수토양환경
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• 제15권4호
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• pp.1-12
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• 2010

Well production by a riverbank filtration facility with multi-radial collector well systems in Jeungsan-ri, Changnyeong gun, Korea was evaluated. In this study, the drawdown at collector wells due to pumping and groundwater inflow rates along the horizontal arms of the collector wells were computed through numerical simulations. Sensitivities of the well production to hydraulic conductivity and well flow coefficient, which represents the resistance to the flow from the aquifer to the horizontal arms, were analyzed. Simulation results showed that, with given proposed pumping rate conditions, the drawdown in the caisson exceeded maximum drawdown constraints in the study site and the adjustment of the pumping rate at each well is needed. The drawdown is affected by the hydraulic conductivity of the main aquifer and the well flow coefficient, which means the profound field investigation of the study site is needed to accurately estimate the efficiency of riverbank filtration through radial collector wells.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.119-125
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• 2004

Unsteady nonlinear wave motions on the free surface over a plane beach of constant slope are numerically simulated using a finite difference method in rectangular grid system. Two-dimensional Navier-Stokes equations and the continuity equation are used for the computations. Irregular leg lengths and stars are employed near the boundaries of body and free surface to satisfy the boundary conditions. Also, the free surface which consists of markers or segments is determined every time step with the satisfaction of kinematic and dynamic free surface conditions. Moreover, marker-density method is also adopted to allow plunging jets impinging on the free surface. The second-order Stokes wave theory and solitary wave theory are employed for the generation of waves on the inflow boundary. For the simulation of wave breaking phenomena, the computations are carried out with the plane beach of constant slope in surf zone. The results are compared with each other. The marker-density method is better then the hybrid method. Also they are compared with other existing experimental results. The Agreement between the experimental data and the computation results is good.

• 한국항해학회지
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• 제14권2호
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• pp.15-31
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• 1990

Recently, there is a tendency to design the large full ships with lower-powered engine as the means for energy saving in ship's navigation at seas. Such a lower-powered ship is anticipated to show the different propulsive performance in rough seas, because the fluctuation of main engine load of lower powered ship is relatively large as compared with higher-powered ship is relatively large as compared with higher-powered ship. The fluctuation of propeller load is nonlinear at racing condition in waves. It is due to the variation of inflow velocity into propeller, the propeller immersion and the characteristics of engine governor. In this paper, the theoretical calculation of the nominal speed loss and the numerical simulation for the nonlinear load fluctuation of a model ship in rough seas are carried out. From the results of calculation, the following are discussed. (1) The ratio of nominal speed loss to the speed in still water. (2) The manoeuvring ability of ship and the operational ability of main engine in a seaway. (3) A method of the evaluation for the fluctuation of propeller torque and revolution on the engine characteristics plane. (4) The effect of engine governor characteristics on the propeller load fluctuation.

• 한국농공학회지
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• 제33권4호
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• pp.52-60
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• 1991

This study was conducted to investigate the appropriate operation method minimizing the deviation between irrigation water demand and release from the reservoirs, and the simulation technique was used in the operation model. This model was applied to the grouped reservoirs system consisted of Dongsang, Daia and Keungchun reservoirs and Eowoo-weir in Chonbuk FLIA district. The results obtained in this study are summarized as follows; 1.The area above the Eowoo weir point was divided into 6 small watersheds, and daily inflows from each watershed were calculated by Tank model. It showed that the average annual runoff ratio was 40-60% respectively. 2.Based on the Blaney-Criddle formula daily water requirement of Chonbuk FLIA irrigation area was estimated, mean water requirement for paddy field during the irrigation period was 818.lmm. 3.Using the basic data such as inflow and water demand, four different release types were selected. Through the simulated operation the difference between intake water required at Eowoo-weir point and release from the 3 reservoirs was estimated. The best result was obtained when Daia and Keungchun reservoirs are operated parallelly at fixed release ratio and the release of Dongsang reservoir was determined according to the storage of Daia reservoir.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 춘계학술발표대회 논문집
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• pp.184-189
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• 2008

These days, Apartment is altered oversized and high-rise through construction techniques development. Also, the cost of cooling and heating load would be expected by balcony expansion into inner space caused by legalization. In specially, HVAC systems of high-rise residential building almost apply to pre-existence techniques of middle and low residential building except for consideration and methods of the air inflow minimization into indoor through mechanical ventilation is used in ventilation system. From these cause, window systems of high-rise apartments stands high in estimation of components. Thus, purpose of this study is to make a comparative study through difference of window systems.

• 물과 미래
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• 제29권5호
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• pp.129-138
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• 1996

Loopnet은 폐합형수계에서 물의 흐름에 관한 시간적 공간적 변화를 계산할 수 있는 부정류 해석프로그램이다. 본 연구에서는 이 모형이 적용하고 있는 Looped Solution 알고리듬을 유도하고, 폐합형수계의 시험하도를 구성하여 이 모형의 안정성 및 정확성을 시험해 보았다. 또한 굴포천 유역을 대상으로 이 모형을 적용하여 수공 구조물, 서해측의 조위와 유역의 홍수 유입 등을 고려한 홍수위를 산정하였다. 그 결과 모형의 안정성 및 정확성 시험에서 신뢰할 만한 결과를 얻을 수 있었으며, 운하의 운영수위는 굴포천 본류와 방수로구간 모두 홍수위 변화에 큰 영향을 미치지 못하였으나, 조도계수는 홍수위 변화에 중요한 물리적 요소 중 하나로 분석되었다.

• Water Engineering Research
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• 제5권2호
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• pp.101-109
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• 2004

Aggregating information by combining forecasts from two or more forecasting methods is an alternative to using forecasts from just a single method to improve forecast accuracy. This paper describes the development and use of a monthly inflow forecast model based on an optimal linear combination (OLC) of forecasts derived from naive, persistence, and Ensemble Streamflow Prediction (ESP) forecasts. Using the cross-validation technique, the OLC model made 1-month ahead probabilistic forecasts for the Chungju multi-purpose dam inflows for 15 years. For most of the verification months, the skill associated with the OLC forecast was superior to those drawn from the individual forecast techniques. Therefore this study demonstrates that OLC can improve the accuracy of the ESP forecast, especially during the dry season. This study also examined the value of the OLC forecasts in reservoir operations. Stochastic Dynamic Programming (SDP) derived the optimal operating policy for the Chungju multi-purpose dam operation and the derived policy was simulated using the 15-year observed inflows. The simulation results showed the SDP model that updated its probability from the new OLC forecast provided more efficient operation decisions than the conventional SDP model.

• Wind and Structures
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• 제7권3호
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• pp.159-172
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• 2004

The study of how buildings affect wind flow is an important part of the research being conducted on urban climate and urban air quality. NJU-UCFM, a standard $k-{\varepsilon}$ turbulence closure model, is presented and is used to simulate how the following affect wind flow characteristics: (1) an isolated building, (2) urban canyons, (3) an irregular shaped building cluster, and (4) a real urban neighborhood. The numerical results are compared with previous researchers' results and with wind tunnel experiment results. It is demonstrated that the geometries and the distribution of urban buildings affect airflow greatly, and some examples of this include a changing of the vortices behind buildings and a "channeling effect". Although the mean air flows are well simulated by the standard $k-{\varepsilon}$ models, it is important to pay attention to certain discrepancies when results from the standard $k-{\varepsilon}$ models are used in design or policy decisions: The standard $k-{\varepsilon}$ model may overestimate the turbulence energy near the frontal side of buildings, may underestimate the range of high turbulence energy in urban areas, and may omit some important information (such as the reverse air flows above the building roofs). In ideal inflow conditions, the effects of the heights of buildings may be underestimated, when compared with field observations.

• 한국수소및신에너지학회논문집
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• 제24권4호
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• pp.326-333
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• 2013

This paper presents the performance enhancement of a double-inlet centrifugal blower by the shape optimization of an inlet duct. Two design variables, a length of anti circulation vane and an angles of inlet guide, are introduced to improve the inlet flow uniformity leading to the blower performance. Three-dimensional Navier-Stokes equations are used to analyze the blower performance and the internal flow of the blower. From the shape optimization of the inlet duct of the double-inlet centrifugal blower, the optimal positions of each design variable are determined. Throughout the analysis of sensitivity, it is found that the angle of the inlet guide is more effective than the length of the anti-circulation vane to increase flow uniformity at the outlet of the duct. Efficiency and pressure for the optimal inlet duct shape are successfully increased up to 3.55% and 3.2% compared to those of reference blower at the design flow condition, respectively. Detailed flow field inside the blower is also analyzed and compared.

• 한국환경과학회지
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• 제29권10호
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• pp.969-979
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• 2020

A numerical simulation was conducted on perfluorooctane sulfonate (PFOS) in the Gwangyang Bay using a multi-box model to estimate the transport of organic chemicals in the coastal environment. The results of the sensitivity analysis on dissolved PFOS and PFOS in Particulate Organic Carbon (POC) indicate that they were most significantly influenced by the adsorption rate, desorption rate, and sinking velocity coefficients. PFOS in phytoplankton was found to be sensitive to bio-concentration and the excretion rate. The results of the mass balance indicate that the standing stocks of PFOS in water, POC, and phytoplankton are 345.55 g, 63.76 g, and 0.11 g, respectively, in the inner part and 149.90 g, 27.51 g, and 0.05 g, respectively, in the outer part. Considering flux in the inner part, adsorption to POC had the highest value among transition paths. The next highest were desorption, outflow to the outer part, and inflow to the inner part. Outflow into the open sea was found to have the highest value for the outer part.