3차원 수치모의를 통한 침사지에서의 부유사 밀도류 해석

안상도,김기호,박원철,Van Thinh Nguyen 대한상하수도학회 2013 상하수도학회지 Vol.27 No.3

A sedimentation basin is used to remove suspended sediments which can cause abrasive and erosive wear on hydraulic turbines of hydropower plants. This sediment erosion not only decreases efficiency of the turbine but also increases maintenance costs. In this study, the three-dimensional numerical simulations were carried out on the overseas hydropower project. The simulations of flow and suspended sediment concentration were obtained using FLOW-3D computational fluid dynamics code. The simulations provide removal efficiency of a sedimentation basin based on particle sizes. The influence of baffles on the flow field and the removal efficiency of suspended sediments in the sedimentation basin has been investigated. This paper also provides the numerical simulations for sediment-induced density currents that may occur in the sedimentation basin. The simulation results indicate that the formation of density currents decreases the removal efficiency. When a baffle is installed in the sedimentation basin, the baffle provides intensive settling zones resulting in increasing the sediments settling. Thus the enhanced removal efficiency can be achieved by installing the baffle inside the sedimentation basin.

²¹⁰Pb 연대측정에 의한 일본 타호부호수의 토사퇴적속도 변화 분석

안영상,안기완,이계한,나카무라 후쯔시,Ahn, Young Sang,An, Ki-Wan,Lee, Kye-Han,Nakamura, Futoshi 한국산림과학회 2014 한국산림과학회지 Vol.103 No.1

$^{210}Pb$ dating was conducted to examine the influence of land use changes in the forest catchment on lake sedimentation. The Kushiro River, into which Lake Takkobu drains under regular flow conditions, contributed to an increased sedimentation rate in sampling point at the lake outflow because turbid water from the Kushiro River flows back into Lake Takkobu during floods. The elevated sediment flux from the catchment dilutes the $^{210}Pb$ concentration in sampling points at the inflow of the Takkobu River and the lake outflow, which causes fluctuations in the $^{210}Pb$ concentrations in sediment cores. The $^{210}Pb$ dating was estimated using the CRS (Constant rate of Supply) model. The dates by the CRS model in Lake Takkobu profiles were in good agreement with the dates by $^{137}Cs$. Sedimentation rates reconstructed for the past 100-150 years suggested that sedimentation rates increased drastically following land use changes. While a natural sedimentation rate of $0.01-0.03g/cm^2/year$ is observed until the 1880s, whereas lake sedimentation accelerated to $0.03-0.09g/cm^2/year$ following land use changes such as deforestation and channelization, between the 1880s and 1940s. In particular, the sedimentation rates have been associated with deforestation, channelization, agricultural development and road construction, since the 1980s, and these rates were about 9-28 times higher than those under natural conditions, leading to accelerated lake shallowing. 산림유역의 토지이용 변화가 호수의 토사퇴적속도에 미치는 영향을 조사하기 위해 $^{210}Pb$ 연대측정을 수행하였다. 평상시 타코부호수는 쿠시로강으로 유출되지만 쿠시로강의 수위가 증가하면 역류현상으로 인해 쿠시로강에 유출된 다량의 세립토사가 호수로 유입되고 있어 호수 유출지점의 토사퇴적속도를 증가시키고 있었다. 그래서 호수에서 유출입하는 하천 주변의 토사퇴적물에서 $^{210}Pb$ 농도는 많은 양의 토사 퇴적의 영향으로 $^{210}Pb$ 농도가 희석되어 비교적 낮은 값을 나타내고 있었으며 지수함수적으로 감소하는 경향도 나타나지 않았다. 따라서 본 연구에서는 CRS 모델의 $^{210}Pb$ 연대측정법을 사용하였고, CRS 모델의 연대는 $^{137}Cs$ 연대(1963년)와 잘 일치하였다. 타코부호수에서 과거 100~150년 정도의 토사퇴적속도를 조사한 결과, 유역에서 인위적 개발이 없는 1880년대 이전 자연상태에서는 토사퇴적량이 $0.01{\sim}0.03g/cm^2/year$였고, 산림벌채와 하천공사가 시작된 1880년대~1940년대에는 $0.03{\sim}0.09g/cm^2/year$으로 토사퇴적이 증가하였다. 특히 유역에서 산림벌채, 하천공사, 농업개발과 임도 개설이 진행된 1980년대 이후에는 토사퇴적속도가 $0.09{\sim}0.84g/cm^2/year$로 자연상태보다 9~28배 증가하여 호수의 수심이 얕아지는 현상을 가속시키고 있는 것으로 나타났다.

경사판 칩전지의 효율 특성에 관한 연구

양원영(Yang Won-Young) 한국지적정보학회 2002 한국지적정보학회지 Vol.4 No.-

본 연구에서는 경사판침전지의 효율특성을 파악하고자 일반침전지와의 비교실험을 하였다. 경사판침전지의 실험조건이 각각의 경사판 각도 60˚, 70˚, 80˚, 90˚로 변화를 주었고, 경사판과 경사판 간격은 100㎜로 선정하여 실험을 하였다. 그리고, 일반침전지를 경사판침전지의 동일 조건에서 실험을 실시하였다. 실험결과는 경사판침전지가 경사판 각도 60˚ 이고 경사판간격 100㎜일 때, 일반침전지의 침전효율은 62%이고 경사판침전지의 71%로 경사판침전지가 일반침전지보다 효율면에서 9% 침전효율이 높은 것으로 나타났다. 따라서, 현재 대부분의 정수장에서 일반침전지를 적용하고 있는데, 앞으로 경사판침전지에 대해 많은 연구가 이루어진다면, 보다 침전효율이 높은 침전지를 정수장을 기획, 설계하는데 도움이 될 것으로 판단된다. In this paper, in order to know sedimentation efficiency of normal sedimentationㆍinclination plate sedimentation compared with laboratory test. According to inclination plate's angle of inclination plate sedimentation, as a result of laboratory get most optimized inclination plate in laboratory is inclination plate with 60° angle, and 100㎜ interval of inclination plate. Sedimentation efficiency of normal sedimentationㆍinclination plate sedimentation is 62% and 71%. Also. the rate of sedimentation was increased 9%. As a conclude, From now on, Inclination plate sedimentation requirement in study.

사각형 중간맨홀에서의 유사 퇴적 분석 및 산정식 제안

김정수,송주일,임창수,윤세의 대한상하수도학회 2012 상하수도학회지 Vol.26 No.2

Sediment load deposited in sewers and manholes reduces not only the capacity of pipes but also the efficiency of the whole sewer system. This causes the inundations of the low places and overflows at manholes, Moreover, sulfides and bad odor can occur due to deposited sediment with organic loads in manholes. Movements of sediment load in manholes are complicated depending on manhole size, location, inside structure, sediment load type, and time. Therefore, it is necessary to understand the movements of sediment load in manholes by experiments. In this study, experiments were implemented by a square manhole with straight path to measure deposited sedimentation quantity. The experimental apparatus was consisted of a high water tank, an upstream tank, test pipes, a sediment supplier, a manhole, and a downstream tank to measure the experimental discharge. The quantity of deposited sediment load was measured by different conditions, such as the inflow condition of sediment(continuous and certain period), the amount of inflow sediment, discharge, and the type of sediment. Jumoonjin sand(S=2.63, D50=0.55mm), general sand(GS, S=2.65, D50=1.83mm) and anthracite (S=1.45, D50= 0.80mm) were employed for the experiment. The velocities in inflow pipe were 0.45 m/s, 0.67 m/s, and 0.9 m/s. Sediment load movement and sedimentation quantity in manhole were influenced by many factors such as velocity, shear stress, viscosity, amount of sediment, sediment size, and specific gravity. Suggested regression equations can estimated the quantity of deposited sediment in the straight path square manholes. The connoted equations that were evaluated through the experimental study have velocity range from 0.45 to 0.9m/sec. The study results illustrates that appropriation of design velocity ragne between 1.0 and 2.0m/sec could implement to maintain and manage manholes.

A discrete element model for the influence of surfactants on sedimentation characteristics of magnetorheological fluids

손권중 한국유변학회 2018 Korea-Australia rheology journal Vol.30 No.1

Hindering particle agglomeration and re-dispersion processes, gravitational sedimentation of suspended particles in magnetorheological (MR) fluids causes inferior performance and controllability of MR fluids in response to a user-specified magnetic field. Thus, suspension stability is one of the principal factors to be considered in synthesizing MR fluids. However, only a few computational studies have been reported so far on the sedimentation characteristics of suspended particles under gravity. In this paper, the settling dynamics of paramagnetic particles suspended in MR fluids was investigated via discrete element method (DEM) simulations. This work focuses particularly on developing accurate fluid-particle and particle-particle interaction models which can account for the influence of stabilizing surfactants on the MR fluid sedimentation. Effect of the stabilizing surfactants on interparticle interactions was incorporated into the derivation of a reliable contact-impact model for DEM computation. Also, the influence of the stabilizing additives on fluid-particle interactions was considered by incorporating Stokes drag with shape and wall correction factors into DEM formulation. The results of simulations performed for model validation purposes showed a good agreement with the published sedimentation measurement data in terms of an initial sedimentation velocity and a final sedimentation ratio.

Numerical Modeling of Long Term Reservoir Sedimentation in Semi-two Dimensional Manner

안정규,Chang Geun Song 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.1

Reservoir sedimentation reduces the benefits from the storage of fresh water. The volume and distribution of sediment deposition must be predicted for a long term reservoir operation plan. Either or both experimental and numerical modeling can be applicable for an evaluation of reservoir sedimentation. Because sedimentation occurs along entire reservoirs and throughout the reservoir life span, a one-dimensional numerical sediment transport model, GSTARS, was considered in this study. Even though the model is not a truly two or three dimensional one, the model has capability of simulating channel geometric change in a semi-two dimensional manner using the stream tube concept. In this study, the effect of the number of stream tubes on the performance of the numerical simulation was analyzed using 14 years of real reservoir sedimentation data, and reasonable results were produced with three stream tubes. The densities of the deposited sediment depend on the reservoir operation scheme, especially for clay and silt. It was found that the predicted results vary with the density, and the prediction with various density with respect to location is required for a study reach where reservoir and river regions exit together.

연구논문 : 파키스탄 파트린드댐의 저수지 퇴사관리를 위한 배사효과 분석

노준우 ( Joon Woo Noh ),박진혁 ( Jin Hyeog Park ),허영택 ( Young Teck Hur ),김상호 ( Sang Ho Kim ) 한국물환경학회(구 한국수질보전학회) 2013 한국물환경학회지 Vol.29 No.6

Reservoir sedimentation is one of the major concerns for sustainable reservoir operation. Since sediment concentration of the rivers in the Himalayan Mountain is very high, a proper sediment management scheme is mecessary. This paper presents long-term reservoir sedimentation and sediment flushing based on the gate operation. Focused on the reservoir to be constructed for the Patrind hydropower project in Pakistan, 4 different flushing scenarios were proposed in this study to prevent successive sedimentation. By extending flushing period and by increasing the flushing discharge for 2 times, the flushing rate increases up to 53.2% and 43.6% in proportion to flushing period and dischrge, respectively. Based on the simulation presented in this paper, it is expected to establish efficient sediment management plan to increase hydro power generation and sediment flushing simultaneously.

안면도 할미섬 주변의 침식·퇴적환경 변화 분석

김장수 ( Jang Soo Kim ),장동호 ( Dong Ho Jang ) 한국지형학회 2012 한국지형학회지 Vol.19 No.2

본 연구는 기준목 측정값과 입도분석자료, 풍향 및 풍속자료를 이용하여 안면도 할미섬 주변의 침식 및 퇴적환경 요인을 분석하였다. 할미섬 주변의 퇴적 및 침식환경 변화를 관찰하기 위해 할미섬 주변 12곳에 기준목을 설치하고 2010년 5월 16일부터 2012년 5월 8일까지 총 32회의 현장실측을 실시하였다. 현장실측 결과 H-3, H-4, H-5, H-9 지점은 퇴적환경이 우세한 것으로 나타났으며, H-7, H-8, H-10, H-11, H-12 지점은 침식환경이 우세한 것으로 나타났다. 반면에 H-2, H-6 지점은 침식과 퇴적이 반복적으로 나타나고 있는 것으로 조사되었다. 이러한 결과는 할미섬의 남서측에 설치된 제방에 의해 해빈의 모래가 할미섬의 북동변으로 이동하지 못하고 이들 지점에 퇴적되었기 때문인 것으로 판단되며, 할미섬 전면의 비치리즈에서 모래를 공급받지 못한 북동측에서는 침식이 우세하게 진행된 것으로 판단된다. 즉 일반적으로 할미섬의 남서측에서는 퇴적이 우세한 반면 북동측에서는 침식이 우세한 것으로 나타났다. 그러나 북동측의 H-9 지점과 남서측의 H-12지점은 반대의 경향이 관찰되었는데, H-9지점의 경우 할미섬에 연결된 사취의 끝단에 위치하고 있어 조류에 의한 퇴적물 공급이 가능했기 때문으로 분석되었다. 반면 사구에 위치한 H-12 지점은 측정기간이 짧아 침식원인에 대한 분석을 내리기가 어려웠다. In this study, we analyzed sedimentation and erosion environment around Halmiseom on Anmyeon Island using wind direction and wind speed data, gain size analysis data and datum-point measured values. To observe changes in sedimentation and erosion environment around Halmiseon, we installed datum points at 12 locations around Halmiseom and carried out at total of 32 field measurements from May 16th, 2010 to May 8th, 2012. The field measurement results showed that H-3, H-4, H-5 and H-9 points are dominated by sedimentation environment, and H-7, H-8, H-10, H-11 and H-12 points are dominated by erosion environment. Meanwhile, sedimentation and erosion appeared alternately at H-2 and H-6 points. These results indicate that a bank installed in the southwest side of Halmiseom prevented sand of the beach from moving to the northeast side, leaving the sand of the beach being deposited at the sites, and the northeast side, where sand was not provided from beach ridge of Halmiseon was dominated by sedimentation. That is, the southwest side of Halmiseom was dominated by sedimentation, but the northeast side was dominated by erosion in general. However, the opposite trends were observed at H-9 point of the northeast side and H-12 point of the southwest side. According to analysis, since H-9 point is located at the end of sand spit connected to Halmiseom, the supply of sediments by a tidal current is possible. On the other hand, it was difficult to analyze the cause of erosion in case of H-12 point located at the sand dune due to the short measurement period.

Semi-two Dimensional Numerical Prediction of Non-Equilibrium Sediment Transport in Reservoir using Stream Tubes and Theory of Minimum Stream Power

안정규,Haw Yen 대한토목학회 2015 KSCE Journal of Civil Engineering Vol.19 No.6

This paper presents numerical modeling methods to predict long term reservoir sedimentation. The Generalized Stream Tube computer models for Alluvial River Simulation version 3.0 (GSTARS3) model which has capability of semi-two dimensional hydraulic computation and sediment routing by using stream tube concept combined with the theory of minimum stream power was implemented. In GSTARS3, non-equilibrium sediment transport equation is incorporated in accounting for the reservoir sedimentation processes. Capability of numerical simulation with and without applying stream tube concept, theory of minimum stream power, and non-equilibrium sediment transport equation was evaluated with nine years of sedimentation in the Kardeh Reservoir, Iran, and the best combinations of theories were investigated in this study. Simulated thalweg profile and channel geometry were compared to the measured results. From the comparisons, non-equilibrium sediment transport equation is preferably recommended method to predict reservoir sedimentation. The application of theory of minimum stream power improved the performance of model predictions significantly. In addition, simulations with three stream tubes were slightly better than the one with five stream tubes. Numerical simulations indicated that a semi-two dimensional modeling with non-equilibrium sediment transport equation, three stream tubes, and theory of minimum stream power is applicable to a long term prediction of reservoir sedimentation.

3분과 : 210Pb 연대측정에 의한 일본 타호부호수의 토사퇴적속도 변화 분석

안영상 ( Young Sang Ahn ),안기완 ( Ki Wan An ),이계한 ( Kye Han Lee ),중촌태사 한국임학회 2014 한국산림과학회지 Vol.103 No.1

산림유역의 토지이용 변화가 호수의 토사퇴적속도에 미치는 영향을 조사하기 위해 210Pb 연대측정을 수행하였다. 평상시 타코부호수는 쿠시로강으로 유출되지만 쿠시로강의 수위가 증가하면 역류현상으로 인해 쿠시로강에 유출된 다량의 세립토사가 호수로 유입되고 있어 호수 유출지점의 토사퇴적속도를 증가시키고 있었다. 그래서 호수에서 유·출입하는 하천 주변의 토사퇴적물에서 210Pb 농도는 많은 양의 토사 퇴적의 영향으로 210Pb 농도가 희석되어 비교적 낮은 값을 나타내고 있었으며 지수함수적으로 감소하는 경향도 나타나지 않았다. 따라서 본 연구에서는 CRS모델의 210Pb 연대측정법을 사용하였고, CRS 모델의 연대는 137Cs 연대(1963년)와 잘 일치하였다. 타코부호수에서 과거 100~150년 정도의 토사퇴적속도를 조사한 결과, 유역에서 인위적 개발이 없는 1880년대 이전 자연상태에서는 토사퇴적량이 0.01~0.03 g/cm2/year였고, 산림벌채와 하천공사가 시작된 1880년대~1940년대에는 0.03~0.09 g/cm2/year으로 토사퇴적이 증가하였다. 특히 유역에서 산림벌채, 하천공사, 농업개발과 임도 개설이 진행된 1980년대 이후에는 토사퇴적속도가 0.09~0.84 g/cm2/year로 자연상태보다 9~28배 증가하여 호수의 수심이 얕아지는 현상을 가속시키고 있는 것으로 나타났다. 210Pb dating was conducted to examine the influence of land use changes in the forest catchment on lake sedimentation. The Kushiro River, into which Lake Takkobu drains under regular flow conditions, contributed to an increased sedimentation rate in sampling point at the lake outflow because turbid water from the Kushiro River flows back into Lake Takkobu during floods. The elevated sediment flux from the catchment dilutes the 210Pb concentration in sampling points at the inflow of the Takkobu River and the lake outflow, which causes fluctuations in the 210Pbconcentrations in sediment cores. The 210Pb dating was estimated using the CRS (Constant rate of Supply) model. Thedates by the CRS model in Lake Takkobu profiles were in good agreement with the dates by 137Cs. Sedimentation rates reconstructed for the past 100-150 years suggested that sedimentation rates increased drastically following land use changes. While a natural sedimentation rate of 0.01-0.03 g/cm2/year is observed until the 1880s, whereas lakesedimentation accelerated to 0.03-0.09 g/cm2/year following land use changes such as deforestation and channelization, between the 1880s and 1940s. In particular, the sedimentation rates have been associated with deforestation, channelization, agricultural development and road construction, since the 1980s, and these rates were about 9-28 times higher than those under natural conditions, leading to accelerated lake shallowing.