• Title/Summary/Keyword: Bed slope

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A Study on Selected Transverse Bed Slope Models in Channel Bend (유로만곡부의 횡방향 하상경사 산정 모형에 관한 연구)

  • Song, Jai Woo;Choi, In Ho;Kim, Ji Ho
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.14 no.6
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    • pp.1395-1404
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    • 1994
  • Transverse bed slope in bend is a subject of scientific investigation since it provides the necessary information for channel design and protection of hydraulic structures (bank, bridge, etc), and study of river morphology. In this paper, selected models were examined and compared for the value of prediction of the transverse bed slope in curved alluvial channels(project area), by using field data, and fitting model was proposed. All models that related the local transverse bed slope to mean flow characteristics were alike in the sense that they predicted the local transverse bed slope to be proportional to the ratio between depth and radius of curvature. The difference among the models was related with the factor of proportionality, K. Also, measured transverse bed slope was correlated to mean velocity, maximum depth, and density Froude number in channel bend. In this paper selected models were compared for the prediction of the transverse bed slope using Odgaard's experiment (obtained in Sacramento River bend), so Odgaard89 model was closely related with real transverse bed slope.

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Research on Relationship of Bed Material and Channel Characteristics (대표 입경과 하도 특성의 관계 분석)

  • Lee, Du-Han;Son, Min-Woo;Kim, Myoung-Hwan;Kim, Chang-Wan
    • Proceedings of the Korea Water Resources Association Conference
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    • 2006.05a
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    • pp.613-617
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    • 2006
  • Bed material in natural streams is affected by geological characteristics of upstream and acting focre by flow of stream. Acting force in streams are also affected by bed slope and discharge of streams. Yamamoto(1994) suggested that channel reaches with similar slope share similar characteristics values in representative bed material size, tractive force, channel width and depth. He also suggested that main factors dominating channel characteristics are mean annual discharge, epresentative bed material size and bed slope. Bed material shows physical and ecological characteristics of channels. In this research, characteristics of bed material in natural or close to natural streams were studied and compared with Janpanese stream data. In the result, characteristics of gravel and sand material can be presented in the term of non-dimensional tractive force, bed slope and bed material size.

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Review on the divergence form for bed slope source term and correction of the volume/free-surface relationship (발산형 바닥 경사 생성항의 재검토와 체적-수위 관계의 수정)

  • Hwang, Seung-Yong
    • Journal of Korea Water Resources Association
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    • v.50 no.5
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    • pp.289-302
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    • 2017
  • DFB (Divergence Form for Bed slope source term) was rigorously derived and the error of mDFB using mean water depth at the cell face in DFB was clearly demonstrated. In addition, DFB technique turned out to be an exact method to the bed slope source term. The existing volume/free-surface relationship to the PSC (Partially Submerged Cell) has been corrected. It was discussed that treatment for the partially submerged edge is required to satisfy the C-property in PSC. It is expected that this study will provides a more accurate means in analyzing the shallow water equations with the approximate Riemann solver.

Development of Transverse Bed Slope Model for Nonuniform Sand Bed at River Bend (만곡부 혼합입경 하상횡경사 모형의 개발)

  • 최종인;고재웅
    • Water for future
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    • v.29 no.4
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    • pp.177-186
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    • 1996
  • The analytical approach to determine transverse sand bed slope at river bend are based on two phases that the flow is considered as fully developed flow and the bed is fluvial having bed load. All existing methods are theoretically derived from the initiation of motion of the particles at river bed. They assume that the Shields parameter has a constant value of 0.06. In this study, the variability of Shields parameter due to the differences of shape of grain size distribution is considered. Therefore the parameter is not a constant, 0.06, but depends on the shape of the grain size distribution. This result gives good agreement to estimate transverse bed slope with actual field data at river bend.

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Flow Characteristics and Transverse Bed Slope in Curved Alluvial Channels (만곡 수로의 횡방향 하상경사와 흐름특성)

  • 차영기;이대철
    • Water for future
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    • v.24 no.1
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    • pp.99-107
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    • 1991
  • This study is for simulating to the model which analyzes flow characteristics and transverse bed slopes in a coarse-streambed of the meandering alluvial channels. Using the equations for conservation of mass, momentum, and for lateral stability of the streambed, a linear differential equation of transverse bed slope is derived from the flow characteristics in curved channels. Its solutions are solved by the Sine-generated curve method(SCM) and compared with results of field measurements. Lag distances by the maximum transverse bed slope and velocity profiles will predict risk sections of concave bank under floods.

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Development of Stream Width and Bed-slope Estimation Equations for Preparing Data for Distributed Storm Runoff Model (분포형 강우-유출모형의 하도자료 구축을 위한 하폭 및 하상경사 산정공식 개발)

  • Jung, In-Kyun;Park, Jong-Yoon;Joh, Hyung-Kyung;Lee, Ji-Wan;Kim, Seong-Joon
    • Journal of The Korean Society of Agricultural Engineers
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    • v.52 no.4
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    • pp.1-10
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    • 2010
  • In this study, two estimation equations for preparing stream data for distributed storm runoff model were developed by analyzing the nonlinear relation between upstream flow-length and stream width, and between upstream flow-length and stream bed-slope. The equations for stream cell were tested in Chungjudam watershed (6,661 $km^2$) using KIMSTORM. Six storm events occurring between 2003 and 2008 were selected for the model calibration and verification before the test of equations. The average values of the Nash-Sutcliffe model efficiency (ME), the volume conservation index (VCI), the relative error of peak runoff rate (EQp), and the difference of time to peak runoff (DTp) were 0.929, 1.035, 0.037, and -0.406 hr for the calibrated four storm events and 0.956, 0.939, 0.055, and 0.729 hr for the two verified storm events respectively. The estimation equations were tested to the storm events, and compared the flood hydrograph. The test result showed that the estimation equation of stream width reduced the peak runoff and delaying the time to peak runoff, and the estimation equation of stream bed-slope showed the opposite results.

A Prediction Model of Transverse Bed Slope in Meandering Rivers (사행하천(蛇行河川)의 횡방향(橫方向) 하상경사(河床傾斜)의 예측모형(豫測模型))

  • Hong, Chang Sun;Chung, Yong Tai
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.11 no.4
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    • pp.81-89
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    • 1991
  • An interesting property of meandering river patterns is that they slowly deform, as bank erosion on one side of a channel and deposition on the other side result in the location of the channel. In this study we used a sine-generated meander pattern proposed by Langbein and Leopold(1966) to develop a solution of a linear, second-order differential equation of transverse bed slope(bed topography) proposed by Odgaard(1986). A new model for transverse bed slope(bed topography), that accounts for the phase lag and the influence of the width to depth aspect ratio, was developed in this study and compared with results of field measurements.

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A Study on the Flame Tilt and Flame Spread due to Up-slope on the Surface Fuel Bed - No wind condition - (경사에 따른 화염각 변화와 지표 화염 확산에 관한 연구 - 무풍조건 기반 -)

  • Kim, Dong-Hyun
    • Journal of the Korean Society of Hazard Mitigation
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    • v.9 no.5
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    • pp.57-62
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    • 2009
  • Flame spread velocity to virgin surface fuel bed on a ground slope increases as the flame gets closer to the slope according to the change of a ground slope angle. The existing studies have generally adopted the theory that flame gets closer to the slope as the slope angle increases, without considering the change of flame tilt against the slope. In this study, experiments were made on the actual characteristics of the flame on slopes of various angles, and as a result, this study offers the flame tilt equation according to the slope angle, and derive correlation between flame tilt and flame spread velocity on slope conditions.

Estimation methods of maximum scour depth in steep gravel-bed bend channel (급경사 자갈하상 만곡수로의 최대세굴심 산정공식 평가)

  • Cho, Jaewoong;Nam, A-Reum;Woo, Tae Young;Park, Sang Deog
    • Journal of Korea Water Resources Association
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    • v.49 no.6
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    • pp.529-536
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    • 2016
  • The existing methods to estimate the maximum scour depth in the bend of steep gravel bed channel have been evaluated by the hydraulic movable-bed experiments. In the $90^{\circ}$ bend steep-slope channel paved with the fluvial gravels which are uniform in size and have a mean diameter of 43mm, the maximum scour depths due to the flow discharge and the gradient of bed slope have been investigated and compared with the scour depth computed from the equations. The local scour has occurred in conditions that the bed slope is steeper than 0.02 and the $F_r$ is greater than 0.95. Except Lacey's equation and Zeller's equation, the existing methods computing the maximum scour depth overestimate the maximum scour depth in the steep channel with the very coarse gravel bed. However, Lacey's equation with the bed material size and Zeller's equation considering the approach channel gradient and the bend angle may be relatively used to estimate the scour depth in bend of the steep gravel-bed river.

Slope and Forest Fuel Effect on Spreading of Forest Fire (산불 확산에 영향을 미치는 임지내 산림연료와 경사도에 관한 연구)

  • 채희문;이찬용
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.5 no.3
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    • pp.179-184
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    • 2003
  • This study investigated the relationship of fuel weight and depth together with slope on the spread of forest fire. Fire spread was faster on the greater slope in forested land. Fire had a greater spread rate with lighter fuel weight. The thickness of the fuel bed and forest fire spread rate were not related. The fire spread rate was closely related to the slope and weight of the fuel bed (significant at 0.01, 0.05, respectively). The thickness of the fuel bed was not significant (0.05).