• Title/Summary/Keyword: infiltration flow

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Rainfall-induced shallow landslide prediction considering the influence of 1D and 3D subsurface flows

  • Viet, Tran The;Lee, Giha;An, Hyunuk;Kim, Minseok
    • Proceedings of the Korea Water Resources Association Conference
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    • 2017.05a
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    • pp.260-260
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    • 2017
  • This study aims to compare the performance of TRIGRS (Transient Rainfall Infiltration and Grid-based Regional Slope-stability model) and TiVaSS (Time-variant Slope Stability model) in the prediction of rainfall-induced shallow landslides. TRIGRS employs one-dimensional (1-D) subsurface flow to simulate the infiltration rate, whereas a three-dimensional (3-D) model is utilized in TiVaSS. The former has been widely used in landslide modeling, while the latter was developed only recently. Both programs are used for the spatiotemporal prediction of shallow landslides caused by rainfall. The present study uses the July 2011 landslide event that occurred in Mt. Umyeon, Seoul, Korea, for validation. The performance of the two programs is evaluated by comparison with data of the actual landslides in both location and timing by using a landslide ratio for each factor of safety class ( index), which was developed for addressing point-like landslide locations. In addition, the influence of surface flow on landslide initiation is assessed. The results show that the shallow landslides predicted by the two models have characteristics that are highly consistent with those of the observed sliding sites, although the performance of TiVaSS is slightly better. Overland flow affects the buildup of the pressure head and reduces the slope stability, although this influence was not significant in this case. A slight increase in the predicted unstable area from 19.30% to 19.93% was recorded when the overland flow was considered. It is concluded that both models are suitable for application in the study area. However, although it is a well-established model requiring less input data and shorter run times, TRIGRS produces less accurate results.

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Effects of the Gas Flow Inside a CVI Reactor on the Densification of a C/C Composite (화학기상침투법 반응로 내부 유동에 따른 탄소/탄소 복합재 밀도화)

  • Kim, Hye-gyu;Ji, Wooseok;Kwon, Hyang Joo;Yoon, Sungtae;Kim, Jung-il
    • Composites Research
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    • v.34 no.4
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    • pp.249-256
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    • 2021
  • In this paper, the densification of a carbon/carbon composite during a chemical vapor infiltration (CVI) process is studied using a chemo-mechanical model. The multi-physics numerical model, developed in the previous research, couples computational fluid dynamics and major chemical reactions in the reactor. The model is especially utilized to study the effect of flow behavior around the preform on the densification. Four different types of "flow-guide" structures are placed to alter the gas flow around the preform. It is shown that the flow pattern and speed around the preform can be controlled by the guide structures. The process simulations demonstrate that the average density and/or density distribution of the preform can be improved by controlling the gas flow around the perform. In this study, a full industrial-scale reactor and process parameter were used.

CONSEQUENCE OF BACKWARD EULER AND CRANK-NICOLSOM TECHNIQUES IN THE FINITE ELEMENT MODEL FOR THE NUMERICAL SOLUTION OF VARIABLY SATURATED FLOW PROBLEMS

  • ISLAM, M.S.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.19 no.2
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    • pp.197-215
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    • 2015
  • Modeling water flow in variably saturated, porous media is important in many branches of science and engineering. Highly nonlinear relationships between water content and hydraulic conductivity and soil-water pressure result in very steep wetting fronts causing numerical problems. These include poor efficiency when modeling water infiltration into very dry porous media, and numerical oscillation near a steep wetting front. A one-dimensional finite element formulation is developed for the numerical simulation of variably saturated flow systems. First order backward Euler implicit and second order Crank-Nicolson time discretization schemes are adopted as a solution strategy in this formulation based on Picard and Newton iterative techniques. Five examples are used to investigate the numerical performance of two approaches and the different factors are highlighted that can affect their convergence and efficiency. The first test case deals with sharp moisture front that infiltrates into the soil column. It shows the capability of providing a mass-conservative behavior. Saturated conditions are not developed in the second test case. Involving of dry initial condition and steep wetting front are the main numerical complexity of the third test example. Fourth test case is a rapid infiltration of water from the surface, followed by a period of redistribution of the water due to the dynamic boundary condition. The last one-dimensional test case involves flow into a layered soil with variable initial conditions. The numerical results indicate that the Crank-Nicolson scheme is inefficient compared to fully implicit backward Euler scheme for the layered soil problem but offers same accuracy for the other homogeneous soil cases.

Slope Stability Analysis of Unsaturated Soil Slopes Due to Rainfall Infiltration (강우침투에 따른 불포화 토사사면의 안정해석)

  • 조성은;이승래
    • Journal of the Korean Geotechnical Society
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    • v.16 no.1
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    • pp.51-64
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    • 2000
  • This paper presents a procedure of calculating a safety factor of the unsaturated slope suffering from the rainfall infiltration. The process of infiltration into a slope due to rainfall and its effect on the behavior of the soil slope are examined by using a two dimensional finite element flow-deformation coupled analysis. A factor of safety is calculated at various elapsed times after the commencement of rainfall as in the following procedure. First, stresses are estimated at each Gaussian point from the coupled finite element analysis. Then, the global stress smoothing method is applied to get a continuous stress field. Based on this stress field, a factor of safety is calculated for a specified slip surface by a stress integration scheme. Then, a search strategy is used to find out a critical slip surface which is associated with the minimum factor of safety. Some numerical examples are analyzed in order to study the effect of hydraulic conductivity on the slope stability during rain-induced infiltration. According to the results, local failure zone can be formed near the slope surface due to inhomogeneous distribution of hydraulic conductivity If the failure zone is once formed, then the region extends until a large amount of slide activates. Therefore the local failure can be neglected no longer in the stability analysis.

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Estimating the return flow of irrigation water for paddies (논의 농업용수 회귀수량 추정에 관한 연구)

  • 임상준;박승우;박창언
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 1998.10a
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    • pp.87-91
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    • 1998
  • Unused irrigation water due to delivery losses and overflow from paddies in an irrigation system, and groundwater releases from infiltration are eventually returned to stream. The estimate of irrigation returnflow is important to streamflow modeling and water resources planning. This study was to field monitor the irrigation water use, streamflow, lateral inflow and ground water level, and to determine the return flow of irrigation water

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Return Flow Rate Estimation of Irrigation for Paddy Culture in Chuncheon Region of the North Han River Basin (북한강 유역 춘천지역의 논 농업용수 회귀율 산정)

  • Choi Joong-Dae;Choi Ye-Hwan
    • KCID journal
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    • v.9 no.2
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    • pp.68-77
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    • 2002
  • Return flow rate of agricultural irrigation for rice culture was investigated in the North Han river basin, Two small paddy watersheds were chosen and irrigation, drainage, infiltration and evapotranspiration were monitored and estimated during the irriga

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Cause Analysis for Reduced Effect of Sewer Pipe Improvement Project Based On Investigation of Interceptor Sewers (차집관로의 조사 및 분석을 통한 하수관로정비 사업의 효과 감소 원인 분석)

  • Chae, Myungbyung;Bae, Younghye;Kim, Hungsoo
    • Journal of Wetlands Research
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    • v.20 no.3
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    • pp.219-226
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    • 2018
  • Interceptor sewer is installed underground near to the river side mostly ofstate-owned land and the management efficiency of public sewage disposal facilities is decreasing as too much infiltration/inflow(I/I) and river flow to interceptor sewer are caused by broken or deteriorated sewer. This also affects the sewer pipeline project and decreases its efficiency. Therefore, the aim of this study is to investigate interceptor sewer which has influence on the reduction of the project effect. The investigation were performed for three study areas. The study includes the investigation of current condition of interceptor sewer(sewer extension, pipe diameter, pipe type, installed year, installed locations, etc), investigation of inside of sewer by CCTV accompanied by pumping and dredging works where required, investigation of inside of manholes by eyes, calculation of pollutant load using the results of investigation of flow quantity and quality. Multipoint investigations were simultaneously performed for flow quantity at confluence area and other investigations were also performed for flow quantity and BOD for interceptor sewer and comparison of pollutant load, investigation of infiltration/inflow(I/I) caused by deterioration of interceptor sewer. As the result of the study, a main reason for reduced effect of sewer pipe improvement project was analyzed as the low-density sewage and I/I in public seweage treatment Facility due to deteriorated and unmanaged interceptor sewers.

Research on the Ground Water Developement in the Region of Choong Nam Province (충남지역의 지하수개발에 관한 조사)

  • 민병섭
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.11 no.4
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    • pp.1827-1831
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    • 1969
  • Resulties of research on the capacity of ground water of 994 concrete-pipe-wells and 97 infiltration-gallerys in ground-water-developement-works region executed from March to Julyin 1969, in Choong Chung Nam Do, and research on the quality of ground water for 88 wells for home-use around of River Geum Area, are as fellows: (1) Thickness of aquifer is no more than 2.85m averagely even at river-overflowed plain, alluvial plain and valley plain area that are estimated to contain ground water mostly. And so, it is guessed that ground water capacity is not much especially. (2) Soil of aquifer of the above area is sand or gravel and it is estimated to be good for ground water developement and its mean permeability coefficient is bout $2.5{\times}10^{-3}$(m/sec), and its porosity is about 33.9%. (3) The quality of ground water is good for irrigation water exception of delta plain area. Warm water plan is to need for irrigation water when water temperature is less than 19 degrees below zero. (4) Prospect of ground water developement, judging from quality and quantity, expects to lay infiltration gallery under the ground at river bed in order to utilize under-flow-water of river bed, river-overflowed plain, alluvial plain and valley plain that ground level is less than 50m. (5) Collectable water volume of under-flow-water of river bed is about 450 to $750m^3/day$ to be able to irrigate 3ha to 5ha of the cultivated land in case that infiltration gallery length is 50m and its depth is about 5m. (6) Collectable water volume at river-overflowed plain, alluvial plain and valley plain area, is estimated $150m^3/day$ to be able to irrigated 1ha of the cultivated land.

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Development of a Kinematic Wave Model to Route Overland Flow in Vegetated Area (II) -Runoff Plot Experiments and Model Application- (초지의 지표면 흐름을 추적하기 위한 Kinematic Wave Model의 개발(II) - 포장실험과 모형의 응용 -)

  • ;W.L.Magette
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.35 no.3
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    • pp.74-80
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    • 1993
  • Runoff simulation tests to investigate the flow mechanics of nonsuomerged overland flow in a natural grass intervening land system were condueted and a modified kinematic wave overland runoff model developed by Choi et al. (1993) was verified. Nonhomogeneity and heterogeneity of the soil, slope, local topography, infiltration, grass density, and the density and activity of the soil microhes and wild animals were the major factors affecting the flow. Streamlines were disturbed by grass stems and small concentrated flows due to the disturbed streamlines and local topography were observed a lot. Relatively larger concentrated flows were observed where bundles of grass were dominant than where individual grasses were growing. Predicted hydrographs were agreed verv well with measured hydrographs. Since the modified model considers grass density in computing flow depth and hydraulic radius, it can be better than existing kinematic wave model if it were used to route nonpoint source pollutant attenuation processes in many grass intervening land systems.

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Estimation of the Irrigation Return Flow of Pumped Water in the Keum River Watershed (금강유역 양수장지구의 농업용수 회귀량 산정)

  • 김영식;박정남;안병기;김태철
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 1999.10c
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    • pp.105-110
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    • 1999
  • Unused irrigation water due to delievery losses and management losses. and ground water releases from infiltration in the paddy irrigation system are eventually returned to the stream. They are called as irrigation return flow. It affects the discharge of drought flow in the down strenamflow. And it may contain chemicals, and threaten streamflow quality . Thus, the accurage estimation of irrigation return flow is important to the streamflow modeling and water resources planning , and also to the control of agriculutral nonpoint source pollution . The irrigation return flow of pumped water was investigated in the Keum river watershed.

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