• Journal of Korean Society on Water Environment
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• v.29 no.6
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• pp.813-824
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• 2013

In this study, sediment pass-through (SPT) from the Sangju Weir and Gumi Weir in the Nakdong River is analyzed numerically using CCHE2D. Sediment delivery is analyzed to predict the sediment discharge rate in the Sangju Weir and Gumi Weir. The sediment discharge from the Sanju Weir is 4,381 tons in the inflow of $3,857m^3/s$, which are 2 year frequency discharge, for 48 hours, and the sediment discharge is 2,766 tons in the inflow of $1,500m^3/s$. The maximum sediment delivery occurs in the immediate downstream of the weir. The sediment discharge from the Gumi Weir is 3,216 tons in the inflow of $5,400m^3/s$, which are 2 year frequency discharge, for 48 hours, and the sediment discharge is 73 tons in the inflow of $3,857m^3/s$. The maximum sediment delivery occurs in the weir. Therefore, the effectiveness of sediment delivery is high in the condition of the 2 year frequency discharge and the gate in the weirs fully are opened.

• Geomechanics and Engineering
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• v.34 no.2
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• pp.155-171
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• 2023

Aiming at the grouting treatment of water inflow in karst conduits, a visualized experiment system for conduit-type grouting blocking was developed. Through the improved water supply system and grouting system, and the optimized multisource information monitoring system, the real-time observation of diffusion and deposition of slurry, and the data acquisition of pressure and velocity during the whole process of grouting were realized, which breaks through the problem that the monitoring element is easy to fail due to slurry adhesion in conventional test system. Based on the grouting experiments in static and flowing water, the diffusion and deposition behavior of the quick-setting slurry under different working conditions were analyzed. The temporal and spatial variation behavior of the pressure and velocity were studied, and the blocking mechanism of the grouting were further revealed. The results showed that: (1) Under the flowing water condition, the counter-flow diffusion distance of slurry was negatively correlated with the flow water velocity and the volume ratio of cement and sodium silicate (C-S ratio), and positively correlated with the grouting volume. The slurry deposition thickness was negatively correlated with the flowing water velocity, and positively correlated with the grouting volume and C-S ratio. (2) The pressure increased slowly before blocking of the flowing water and rapidly after blocking in karst conduits. (3) With the continuous progress of grouting, the flowing water velocity decreased slowly first, then significantly, and finally tended to be stable. According to the research results, some engineering recommendations were put forward for the grouting treatment of the conduit-type water inflow disaster, which has been successfully applied in the treatment project of the China Resources Cement (Pingnan) Limestone Mine. This study provided some guidance and reference for the parameter optimization of grouting for the treatment projects of water inflow in karst conduits.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.1
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• pp.25-36
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• 2008

When constructing subsea underground structures, the influence of high water and seepage pressure acting on the structures can not be neglected. Thus hydro-mechanical coupled analysis should be performed to estimate the behavior of the structures precisely In practice, relaxed rock load is generally used for the design of tunnel concrete lining. A method based on the distribution of local safety factor around a tunnel was proposed for the estimation of a height of relaxed rock mass ($H_{relaxed}$). In this study, the validation of the suggested method is investigated in the framework of hydro-mechanical coupled analyses. It was suggested that inducing inflow by pumping through a drainage well gave more reliable results than inducing inflow with shotcrete hydraulic characteristics in case of rock condition of Class III. In this study, therefore, inducing inflow by pumping through a drainage well are adopted in estimating $H_{relaxed}$ due to a tunnel excavation with the rock condition of Class I, III, and V. Also the estimated $H_{relaxed}$ results are compared with those of the existing suggested methods. As the result of this study, it is confirmed that estimating $H_{relaxed}$ based on the distribution of local safety factor around a tunnel can be effectively used even for the case of hydro-mechanical coupled analysis. It is also found that inducing inflow pumping through a drainage well gives more precise and consistent Hrelaxed of a subsea structure.

• Journal of the Korean Institute of Gas
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• v.22 no.3
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• pp.65-73
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• 2018

Coalbed methane has a nonlinear desorption curve depending on the pressure, so an appropriate production system should be constructed considering this phenomenon. The capacity and specification of the coalbed methane gas production facility are determined by the gas flow rate and pressure in the coalbed, which is the external boundary condition of the system. Thus, it is essential to analyze these characteristics in gas production. The gas inflow equation was calculated using the reservoir flow model and utilized as the boundary condition of the whole production facility in this study. Also, to understand the effect of pressure drop on the gas flow in the production facility, the nodal analysis was performed using the flow analysis simulator of production equipment, and we determined the proper specifications and operating conditions of the production facility. This study presents a design criteria as to production and gathering system capable of effectively transporting coalbed methane.

• Korean Journal of Agricultural Science
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• v.37 no.3
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• pp.481-490
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• 2010

Baekgog reservoir is located in Jincheon county, Chungbuk province, of which full water levels will be heightened from EL. 100.1 m to EL. 102.1 m, and total storages from 21.75 $Mm^3$ to 26.67 $Mm^3$. The simulation for reservoir inflow was conducted by DAWAST model. The annual average irrigation water was estimated to 33.19 $Mm^3$ supplied to 2,975 ha and the instream flows could be allocated with 0.14 mm/d from October to April with annual average of 2.52 $Mm^3$. The operation rule curve was drawn using inflow, irrigation, and instream flow requirements data. The reservoir water storage was simulated on a daily basis in case of both normal and withdrawal limit operation. In case of normal operation, the annual average irrigation water supply increased from 31.95 $Mm^3$ to 33.32 $Mm^3$, the instream water supply from 2.40 $Mm^3$ to 2.44 $Mm^3$, the water storages from 15.74 $Mm^3$ to 19.88 $Mm^3$, and the water supply reliability from 77.3 % to 81.6 %. In case of operation with withdrawal limit, the amount of instream water supply was 2.52 $Mm^3$ from reservoir regardless of the condition while the water storage increased from 16.77 $Mm^3$ to 20.65 $Mm^3$. The irrigation water supply capacity was appropriate for the case of normal operation with 2 m heightened condition. The present instream water supply capacity was 35,000 $m^3$/d (6.86 $Mm^3$/y) while 42,000 $m^3$/d (8.36 $Mm^3$/y) in 2 m heightened condition in case of withdrawal limit operation.

• Journal of Korea Water Resources Association
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• v.41 no.12
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• pp.1219-1230
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• 2008

Stream inflows induced by flood runoffs have a higher density than the ambient reservoir water because of a lower water temperature and elevated suspended sediment(SS) concentration. As the propagation of density currents that formed by density difference between inflow and ambient water affects reservoir water quality and ecosystem, an understanding of reservoir density current is essential for an optimization of filed monitoring, analysis and forecast of SS and nutrient transport, and their proper management and control. This study was aimed to quantify the characteristics of inflow density current including plunge depth($d_p$) and distance($X_p$), separation depth($d_s$), interflow thickness($h_i$), arrival time to dam($t_a$), reduction ratio(${\beta}$) of SS contained stream inflow for different flood magnitude in Daecheong Reservoir with a validated two-dimensional(2D) numerical model. 10 different flood scenarios corresponding to inflow densimetric Froude number($Fr_i$) range from 0.920 to 9.205 were set up based on the hydrograph obtained from June 13 to July 3, 2004. A fully developed stratification condition was assumed as an initial water temperature profile. Higher $Fr_i$(inertia-to-buoyancy ratio) resulted in a greater $d_p,\;X_p,\;d_s,\;h_i$, and faster propagation of interflow, while the effect of reservoir geometry on these characteristics was significant. The Hebbert equation that estimates $d_p$ assuming steady-state flow condition with triangular cross section substantially over-estimated the $d_p$ because it does not consider the spatial variation of reservoir geometry and water surface changes during flood events. The ${\beta}$ values between inflow and dam sites were decreased as $Fr_i$ increased, but reversed after $Fr_i$>9.0 because of turbulent mixing effect. The results provides a practical and effective prediction measures for reservoir operators to first capture the behavior of turbidity inflow.

• International Journal of Fluid Machinery and Systems
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• v.9 no.2
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• pp.137-142
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• 2016

Variable Geometry System (VGS) is widely applied to the nozzle vane for the radial inflow turbine constituting automotive turbochargers for the purpose of optimizing the power output at each operating condition. In order to improve the performance of radial turbines with VGS, it is necessary to clarify the influences of the setting angle of nozzle vane on the internal flow of radial turbine. However, the experimental measurements are considered to be difficult for the flow in radial turbines because of the small size and the high rotational speed. In the present study, the numerical calculations were carried out for the flow in the radial turbine at three operating conditions by applying the corresponding nozzle vane exit angles, which were set up in the experimental study, as the inlet boundary condition. The numerical results revealed the characteristic flow behaviors at each operating condition.

• Journal of Korea Water Resources Association
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• v.53 no.2
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• pp.97-105
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• 2020

Recently, Artificial Neural Network receives attention as a data prediction method. Among these, a Long Shot-term Memory (LSTM) model specialized for time-series data prediction was utilized as a prediction method of hydrological time series data. In this study, the LSTM model was constructed utilizing deep running open source library TensorFlow which provided by Google, to predict inflows of multipurpose dams. We predicted the inflow of the Yongdam Multipurpose Dam which is located in the upper stream of the Geumgang. The hourly flow data of Yongdam Dam from 2006 to 2018 provided by WAMIS was used as the analysis data. Predictive analysis was performed under various of variable condition in order to compare and analyze the prediction accuracy according to four learning parameters of the LSTM model. Root mean square error (RMSE), Mean absolute error (MAE) and Volume error (VE) were calculated and evaluated its accuracy through comparing the predicted and observed inflows. We found that all the models had lower accuracy at high inflow rate and hourly precipitation data (2006~2018) of Yongdam Dam utilized as additional input variables to solve this problem. When the data of rainfall and inflow were utilized together, it was found that the accuracy of the prediction for the high flow rate is improved.

• Korean Journal of Ecology and Environment
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• v.35 no.4 s.100
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• pp.285-294
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• 2002

The purpose of this study was to evaluate the relationships between purification characteristics and hydraulic conditions, and to clarify the basic and essential factors required to be considered in the construction and management of artificial wetland system for the improvement of reservoir water quality. The artificial wetland system was composed of a pumping station and six sequential plants beds with five species of macrophytes: Oenanthe javanica, Acorus calamus, Zizania latifolia, Typha angustifolia, and Phragmites australis. The system was operated on free surface-flow system, and operation conditions were $3,444-4,156\; m^3/d$ of inflow rate, 0.5-2.0 hr of HRT, 0.1-0.2 m of water depth, 6.0-9.4 m/d of hydraulic loading, and relatively low nutrients concentration (0.224-2.462 mgN/L, 0.145-0.164 mgP/L) of inflow water. The mean purification efficiencies of TN ranged from 12.1% to 14.3% by showing the highest efficiency at the Phragmites australis bed, and these of TP were 6.3-9.5% by showing the similar ranges of efficiencies among all species. The mean purification efficiencies of SS and Chl-A ranged from 17.4% to 38.5% and from 12.0% to 20.2%, respectively, and the Oenanthe javanica bed showed the highest efficiency with higher concentration of influent than others. The mean purification amount per day of each pollutant were $9.8-4.1\;g{\cdot}m^{-2}{\cdot}d^{-1}$ in BOD, $1.299-2.343\;g{\cdot}m^{-2}{\cdot}d^{-1}$ in TN, $0.085-1.821\;g{\cdot}m^{-2}{\cdot}d^{-1}$ in TP, $17.9-111.6\;g{\cdot}m^{-2}{\cdot}d^{-1}$ in SS and $0.011-0.094\;g{\cdot}m^{-2}{\cdot}d^{-1}$ in Chl-a. The purification amount per day of TN revealed the hi링hest level at the Zizania latifolia bed, and TP showed at the Acrous calamus bed. SS and Chl-a, as particulate materials, revealed the highest purification amount per day at the Oenanthe javanica bed that was high on the whole parameters. It was estimated that the purification amount per day was increased with the high concentration of influent and shoot density of macrophytes, as was shown in the purification efficiency. Correlation coefficients between purification efficiencies and hydraulic conditions (HRT and inflow rate) were 0.016-0.731 of $R^2$ in terms of HRT, and 0.015-0.868 of $R^2$ daily inflow rate. Correlation coefficients of purification amounts per day with hydraulic conditions were 0.173-0.763 of Ra in terms of HRT, and 0.209-0.770 daily inflow rate. Among the correlation coefficients between purification efficiency and hydraulic condition, the percentages of over 0.5 range of $R^2$ were 20% in HRT and in daily inflow rate. However, the percentages of over 0.5 range of correlation coefficients ($R^2$) between purification amount per day and hydraulic conditions were 53% in HRT and 73% in daily inflow rate. The relationships between purificationamount per day and hydraulic condition were more significant than those of purifi-cation efficiency. In this study, high hydraulic conditions (HRT and inflow rate) are not likely to affect significantly the purification efficiency of nutrient. Therefore, the emphasis should be on the purification amounts per day with high hydraulicloadings (HRT and inflow rate) for the improvement of eutrophic reservoir withrelatively low nutrients concentration and large quantity to be treated.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.2
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• pp.177-189
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• 2012

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.