• Journal of Korea Water Resources Association
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• v.39 no.12 s.173
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• pp.1023-1030
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• 2006

The characteristics of the longitudinal velocity in a $180^{\circ}$ constant-radius, recirculating laboratory channel were investigated. Three-dimensional velocity fields were measured using a side-looking ADV. The shortcomings of existing equations for longitudinal velocity are discussed. An eddy viscosity model is adopted in the downstream momentum equation. A mathematical equation was developed to describe the vertical distribution of longitudinal velocity. The comparisons of the longitudinal velocity show generally good agreement. It is found that the curvature change in the curved channel affects the vertical location of maximum velocity and the vertical profile of longitudinal velocity.

• Journal of Korea Water Resources Association
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• v.30 no.5
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• pp.467-475
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• 1997

In this study, breakwater model which has several outlet pipes to discharge heated water is settled in the experimental open channel and velocity distribution of wall jet is measured. Numerical simulation of velocity structure of wall jet using 3-dimensional computer model. Fluent model, is also carried out. The calculated results are verified with the experimental results and the flow characteristics of wall jet are investigated. The length of zone of flow establishment of wall jet is shorter than that of free jet, and the diminution rate of jet centerline longitudinal velocity is larger than that of free jet. Characteristics of buoyant jet and non-buoyant simple jet simulated by Fluent model are compared. Near the outlet pipe, in the region where x/lQ is over 15, this is reversed. Comparison of vertical distribution of longitudinal velocity shows that positive velocity of non-buoyant jet is bigger than that of buoyant jet in the bottom layer and in the upper layer, negative velocity of non-buoyant jet is bigger too. Flow separation in free surface of the buoyant jet occurs in smaller distances from the outlet than the non-buoyant jet. Buoyant jet expands faster than the non-buoyant jet in vertical direction.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.799-802
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• 2008

General behaviors based on hydraulic characteristics of natural streams and channels have been recently analyzed and developed via various numerical models. However in the states of natural hydraulics, an experimental research must be performed simultaneously with the mathematical analysis due to effects of hydraulic properties such as meander, sediment, and so on. In this study based on 2-D advection-dispersion equation, flow and tracer experiments were performed in the S-curved meandering laboratory channel with a rectangular cross-section. The channel was equipped with instrument carriages which was equipped with an auto-traversing system to be used with velocity measuring sensors throughout the depth and breadth of the flow field. To measure concentration distribution of the salt solution was adjusted to that of the flume water by adding methanol and a red dye (KMnO4) was added to aid the visualization of the tracer cloud, the tracer was instantaneously injected into the flow as a full-depth vertical line source by the instantaneous injector and the initial concentration of the tracer was 100,000 mg/l. The secondary current as well as the primary flow pattern was analyzed to investigate the flow distribution in the meandering channels. The velocity distribution of the primary flow for all cases skewed toward the inner bank at the first bend, and was almost symmetric at the crossovers, and then shifted toward the inner bank again at the next alternating bend. Thus, one can clearly notice that the maximum velocity occurs taking the shortest course along the channel, irrespective of the flow conditions. The result of the tracer tests shows that pollutant clouds are spreading following the maximum velocity lines in each cases with various mixing patterns like superposition, separation, and stagnation of pollutant clouds. Flow characteristics in each cases performed in this study can be compared with tracer dispersion characteristics with using evaluation of longitudinal and transverse dispersion coefficients(LDC, TDC). As expected, LDC and TDC in meandering parts have been evaluated with increasing distribution and straight parts have effected to evaluate minimum of LDC and TDC due to symmetric flow patterns and attenuations of secondary flow.

• Korean Journal of Ecology and Environment
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• v.35 no.2 s.98
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• pp.79-91
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• 2002

A time variable modeling study was performed for seasonal variations of vertical temperature profiles in the Okjung Lake located in upstream of the Sumjin River. Based on the model structure of the US Army Corps of Engineer's CE-QUAL-W2, the lake was divided into 3 branches, 50 longitudinal segments and 49 vertical layers and vertical profiles of water temperature and current velocity were simulated over one year. The model results were calibrated and verified against vertical profiles of water temperature measured every month from March 1998 to February 1999 at 5 different locations. The model results showed a good agreement with the field measurements. The hydrologic balance during this period was validated by comparing the simulated values of surface elevation level with the measured data. There was some discrepancy in July data between the model results and the fleld measurements. This could be attributed partially to the inadequacy of the model to the highly hydrodynamic nature of water body and partially to the lack of accuracy in local atmospheric temperature data during summer monsoon period. The model results have shown that there was no seasonal over-turn in most part of the Okjung Lake, where water temperature maintained above $4^{\circ}C$ over one year. In the upstream shal-low area (depth<20 meter), however, temperature at surface layer fell below $4^{\circ}C$ and water was frozen such that slight over-turn would occur during winter period. From this study, we concluded that the Okjung Lake is oligomictic. This conclusionis significantly different from the general pattern that the lakes located from $20^{\circ}C$ to $40^{\circ}C$ latitude would be warm monomictic. From the examination of simulated current velocity distribution, it was found that the upstream inflows would infiltrate into mesolimnion of the lake during hydrodynamic summer monsoon periods due to the thermal density of water.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.3
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• pp.313-319
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• 2009

The blasting has a lot of economic efficiency and speediness but it can damage to a neighbor structure, a domestic animal and a cultured fish due to the blasting vibration, then the public grievance is increased. Therefore, we need to manage the blasting vibration efficiently. The prediction of the correct vibration velocity is not easy because there are lots of different kinds of the scale of blasting vibration and it has a number of a variable effect. So we figure the optimum line through the least-squares regression by using the vibration data measured in hard rock blasting and compared with the design vibration prediction equation. As a result, we confirm that the vibration estimated in this paper is bigger than the design vibration prediction equation in the same charge and distance. If there is a Gaussian normal distribution data on the left-right side of the least squares regression, then we can estimate the vibration prediction equation on reliability 50%(${\beta}=0$), 90%(${\beta}=1.28$), 95%(${\beta}=1.64$). 99.9%(${\beta}=3.09$). As a result, it appears to be suitable that the reliability is 99% at the transverse component, the reliability 95% is at the vertical component, the reliability 90% is at the longitudinal component and the reliability is 95% at the peak vector sum component.

• Journal of Korea Water Resources Association
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• v.46 no.11
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• pp.1115-1128
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• 2013

The purpose of this study is to evaluate the suspended solids and eutrophication processes relationships in Chungju lake using CE-QUAL-W2, two-dimensional (2D) longitudinal/vertical hydrodynamic and water quality model. For water quality modeling, the lake segmentation was configured as 7 branches system according to their shape and tributary distribution. The model was calibrated (2010) and validated (2008) using 2 years of field data of water temperature, suspended solids (SS), total nitrogen (TN), total phosphorus (TP) and algae (Chl-a). The water temperature began to increase in depth from April and the stratification occurred at about 10 m early July heavy rain. The high SS concentration of the interflow density currents entering from the watershed was well simulated especially for July 2008 heavy rainfall event. The simulated concentration range of TN and TP was acceptable, but the errors might occur form the poor reflection for sedimentation velocity of nitrogen component and adsorption-sediment of phosphorus in model. The concentration of Chl-a was simulated well with the algal growth patterns in summer of 2010 and 2008, but the error of under estimation may come from the use of width-averaged velocity and concentration, not considering the actual to one side inclination by wind effect.