• Spatial Information Research
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• 제15권4호
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• pp.397-406
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• 2007

도시지역의 2차원 모형은 홍수침수과정에 있어서 아직 선구적인 분야이며 이러한 모형은 지형 및 불충분한 지형계수 및 자료로 인하여 제한적으로 이용되고 있다. 본 연구에서는 도시지역의 DEM에 기초한 제방 붕괴로 인한 표면수의 침수를 재현하고자 한다. 도시지역에 있어서 표면수의 흐름은 Saint-Venant의 방정식을 통해 모형을 구성하였다. 2002년 삼척시에서 발생한 홍수를 재현하기 위하여 추적자를 이용한 수리모형실험을 수행하여 모형을 보정하였다. 본 연구는 향후 홍수지도 제작이나 도시지역에서 침수에 따른 경제적 손실을 평가하는데 유용하게 이용될 것이다.

• Computers and Concrete
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• 제34권2호
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• pp.137-149
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• 2024

In order to study the triaxial mechanical behavior of steel fiber reinforced high performance concrete (SFRHPC), the standard triaxial compression tests with four different confining pressures are performed on the cylindrical specimens. Three different steel fiber volumes (0, 1% and 2%) are added in the specimens with diameter of 50 mm and height of 100 mm. Test results show that the triaxial compressive strength and peak strain increase with the increasing of fiber content at the same confining pressure. At the same steel fiber content, the triaxial compressive strength and peak strain increases with the confining pressure. The compressive strength growth rate declines as the confining pressure and steel fiber content increases. Longitudinal cracks are dominant in specimens with or without steel fiber under uniaxial compression loading. While with the confining pressure increases, diagonal crack due to shear is obvious. The Mohr-Coulomb criterion is illustrated can be used to describe the failure behavior, and the cohesive force increases as steel fiber content increases. Finally, the numerical model is built by using the PFC3D software. In the numerical model a index is introduced to reflect the effect of steel fiber content on the triaxial compressive behavior. The simulating stress-strain curve and failure mode of SFRHPC are agree well with the experimental results.

• 드라이브 ㆍ 컨트롤
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• 제20권2호
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• pp.1-6
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• 2023

This study aims to develop a Korean dental chair hydraulic circuit by improving the existing equipment in order to localize foreign leading companies' products. The suggested Hydraulic circuit can be applicable to varied sectors where height and backrest angle control of chair-type equipment are required. The study followed the steps below. First, three kinds of foreign hydraulic circuits were analyzed and three kinds of Korean dental chair hydraulic circuits were suggested. Second, it was determined whether the three kinds of Korean hydraulic circuits operate normally through SimulationX, a software specialized in multi domain analysis, and the effectiveness of each circuit was examined.

• 한국환경보건학회지
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• 제26권4호
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• pp.97-104
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• 2000

The purpose of this is made an examination of phosphorus loading model for eutrophication response in the Yongsan lake. For the model, we measured the total amount of nutrients derived from the Yongsan river watershed, inflow rate to the Yongsan lake, water quality, and water budget from January to December in 1999. The total amount of precipitation in the Yongsan river watershed was 4,951.7$\times$10$^{6}$ ㎥/y and inflow amount was 2,569.7$\times$10$^{6}$ ㎥/y, therefore the outflow rate of the Yongsan river watershed was 51.9%. The develop loading of total nitrogen was 86,928.1kg/d and that of total phosphorus was 22,007.6kg/d at the Yongsan river watershed, But, as the inflow loading of total nitrogen was 33,962kg/d and the inflow loading of total phosphorus was 2,218kg/d to the Yongsan lake. so each infolw rate was 39.0% and 10.1%. The hydraulic residence time was 34days, total phosphorus loading [L(P)] on the surface area was 23.398g/㎥/y, the hydraulic load( $Q_{s}$) of inflow water was 74.269m/y, the reserve rate of phosphorus in the lake was 0.359, and the settinh velocity of phosphorus was 0.114m/d at the Yongsan lake. Mathematical model of phosphorus loading to estimate the responses of eutrophication at the Yongsan lake is [ $P_{j}$] = 0.838 [L(P)/Q.(1+√ $T_{w}$)$^{-1}$ ] . ] . .

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2023년도 학술발표회
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• pp.35-35
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• 2023

The main reason for its instability is sediment scouring downstream of hydraulic structures. Both physical and numerical models have been used to investigate the influence of soil properties on scour hole geometry. Nevertheless, no research has been conducted on resistance parameters that affect sedimentation and erosion. In addition, auxiliary structures like wing walls, which are prevalent in many real-world applications, have rarely been studied for their impact on morphology. The hydraulic characteristics of steady flow through a boxed culvert are calibrated using a 3D Computational Fluid Dynamics model compared with experimental data in this study, which shows a good agreement between water depth, velocity, and pressure profiles. Test cases showed that 0.015 m grid cells had the lowest NRMSE and MAE values. It is also possible to quantify sediment scour numerically by testing roughness/d₅₀ ratios (c_s) and diversion walls at a meander flume outlet. According to the findings, c_s = 2.5 indicates a close agreement between numerical and analytical results of maximum scour depth after the culvert; four types of wing walls influence geometrical deformation of the meander flume outlet, resulting in erosion at the concave bank and deposition at the convex bank; two short headwalls are the most appropriate solution for accounting for small changes in morphology. A numerical model can be used to estimate sediment scour at the meander exit channel of hydraulic structures based on the roughness parameter of soil material and headwall type.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.433-449
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• 2021

In this study, a newly enhanced Fluid-Structure Interaction (FSI) model which incorporates mooring lines was used to simulate a floating structure. The model has two parts: a Computational Fluid Dynamics (CFD) model and a mooring model. The open-source CFD OpenFOAM® v1712 toolbox was used in the present study, and the convergence criteria and relaxation method were added to the computational procedure used for the OpenFOAM multiphase flow solver, interDyMFoam. A newly enhanced, tightly coupled solver, CoupledinterDyMFoam, was used to decrease the artificial added mass effect, and the results were validated through a series of benchmark cases. The mooring model, based on the finite element method, was established in MATLAB® and was validated against a benchmark analytical elastic catenary solution and numerical results. Finally, a model which simulates a floating structure with mooring lines was successfully constructed by connecting the mooring model to CoupledinterDyMFoam.

• 상하수도학회지
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• 제27권2호
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• pp.177-184
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• 2013

This study analyzed the hydraulic characteristics of a venturi flume with a circular cone using a 3-D numerical model which uses RANS(Reynolds-Averaged Navier-Stokes Equation) as the governing equation. The venturi flume with the circular cone efficiently measures the discharge in the low-flow to high-flow range and offers the advantage of accurate discharge measurements in the case of a low flow. With no influence of the tail-water depth, the stage-discharge relationship and the flow behaviors were analyzed to verify the numerical simulation results. Additionally, this study reviewed the effect of the tail-water depth on the flow. The stage-discharge relationship resulting from a numerical simulation in the absence of an effect by the tail-water depth showed a maximum margin of error of 4 % in comparison to the result of a hydraulic experiment. The simulation results reproduced the overall flow behaviors observed in the hydraulic experiment well. The flow starts to become influenced by the tail-water depth when the ratio of the tail-water depth to the total head exceeds approximately 0.7. As the ratio increases, the effect on the flow tends to grow dramatically. As shown in this study, a numerical simulation is effective for identifying the stage-discharge relationship of a venturi flume with various types of venturi bodies, including a venturi flume with a circular cone.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2002년도 추계학술발표회
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• pp.28-31
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• 2002

The water level fluctuation (WLF) method is a conventional method for quantifying groundwater recharge by multiplying the specific yield to the water level rise. A 2-D unconfined flow model with a time series of the recharge rate is developed. It is used for elucidating the errors of the WLF method which is implicitly based on the tank model where the horizontal flow in the saturated zone is ignored. Simulations show that the recharge estimated by the WLF method is underestimated for the observation well near the discharge boundary. This is due to the fact that the hydraulic stress resulting from the recharge is rapidly dissipating by the horizontal flow near the discharge boundary Simulations also reveal that the recharge was significantly underestimated with increase in the hydraulic conductivity and the recharge duration, and decrease in the specific yield.

• 한국수소및신에너지학회논문집
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• 제31권4호
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• pp.387-394
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• 2020

A parametric study of a 2.5 kW class propeller type micro hydraulic turbine was performed. In order to analyze the internal flow characteristics in the hydraulic turbine, three dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were used and the hexahedral grid system was used to construct computational domain. To secure the reliability of the numerical analysis, the grid dependency test was performed using the grid convergence index method based on the Richardson extrapolation, and the grid dependency was removed when about 1.7 million nodes were used. For the parametric study, the axial distance at shroud span (L) between the inlet guide vane and the runner, and the inlet and outlet blade angles (β₁, β₂) of the runner were selected as the geometric parameters. The inlet and outlet angles of the runner were defined in the 3 spans from the hub to tip, and a total of 7 geometric parameters were investigated. It was confirmed that the outlet angles of the runner had the most sensitive effect on the power and efficiency of the micro hydraulic turbine.

• 한국수자원학회논문집
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• 제35권5호
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• pp.485-500
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• 2002

본 연구에서는 한강 하류부 및 임진강에서 하천구조물, 조위, 주요 지류 등으로 인해 복잡하게 형성되는 흐름을 해석하기 위한 수리학적 홍수추적모형을 구축하였다. 이를 위해 하천측량 자료를 모형에서 자동적으로 처리할 수 있는 DWOPER-2K 모형을 개발하였다. 감조지역에서 이루어진 실측 조위자료와 최근의 하천측량성과를 이용하여 모형을 구축하였고 잠실수중보와 신곡수중보에서 발생하는 흐름을 효과적 모의할 수 있도록 하였으며 하천구간별 유량규모별로 조도계수를 최적화시켰다. 개발된 모형의 검증결과 한강 및 임진강 하류부에서 복잡하게 발생하는 여러 가지 형태의 흐름을 효과적으로 해석할 수 있는 것으로 나타나 홍수예경보 정확도 향상, 하천관리 등에 효율적으로 사용될 것으로 기대된다.