• Proceedings of the Korea Water Resources Association Conference
• /
• 2004.05b
• /
• pp.453-457
• /
• 2004

본 연구에서는 WES의 표준 월류형 여수로에 대한 동수역학적인 흐름거동을 FLOW-3D 모형을 이용하여 해석하였다. 월류수두에 따른 월류유량, 월류흐름의 수면곡선, 여수로 표면에서의 압력분포와 같은 모의결과는 WES의 실험자료와 잘 일치하였다. 그리고 월류수두가 여수로 설계수두의 1.33배인 경우의 유속과 압력의 연직분포를 검토하였다. 검토결과, 웨어마루를 통과하면서 저층의 유속이 먼저 가속되며 점차 하류로 이동하면서 수표면의 유속이 가속되어 거의 균일한 유속분포를 보였으며, 압력의 연직분포는 웨어마루 상류에서는 수표면에서 내기압을 보이고 점차 수심이 길어짐에 따라 정수압분포와 유사한 분포를 보이나, 여수로 표면에 접근함에 따라 급격하게 압력이 감소하면서 부압이 발생하였다. 웨어마루 하류에서는 여수로 표면에서의 압력이 점차 대기압으로 접근함에 따라, 거의 전 수심에 걸쳐 대기압과 유사한 분포를 보였다.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.11 no.1
• /
• pp.35-41
• /
• 2008

Overtopping wave energy convertor is an offshore wave energy convertor for collecting the overtopping waves converting the water pressure head into electric power through the hydro turbines. This paper presents a numerical wave tank based on the commercial CFD code Fluent. The Reynolds Averaged Naiver-Stokes and VOF model is utilized to generate the 2D numerical linear propagating waves, which has been validated by the analytical solutions. Several incident wave conditions and shape parameters are calculated in the optimal designing investigation of the overtopping characteristics and discharge for the overtopping wave energy convertor.

• Journal of Korea Water Resources Association
• /
• v.37 no.5
• /
• pp.363-373
• /
• 2004

This study analyzed the hydrodynamic flow behavior on a standard ogee spillway with pier by using FLOW-3D. The simulation results were compared with the experiment data of U.S. Army Corps of Engineers - Waterways Experiment Station (WES) and also compared with 2-dimensional simulation results on a spillway without pier. In particular, the characteristics of the distribution of the overflow nappe and pressure in a spillway with pier were investigated in detail. As for the results of the simulation on the flow rate, overflow nappe, and pressure, although there were a few differences in the experiment results of WES, they were identical in most cases in terms of trend. Summarizing the major flow behavior in a standard ogee spillway with pier, first, the water stage at the center line of the bay was higher than that at the side of the bay along the pier. Second, when the water head was larger than the design head of the spillway, at the upstream area of the weir crest, the absolute magnitude of negative pressure occurred highest at the side of the bay along the pier. On the other hand, at the downstream area of the weir crest, the absolute magnitude of negative pressure occurred highest at the centerline of the bay.

• Journal of Korean Society of Water and Wastewater
• /
• v.30 no.2
• /
• pp.147-154
• /
• 2016

The present study used the hydrodynamic numerical model, with the Reynolds-averaged Navier-Stokes equations (RANS) as its governing equations, to analyze overflow characteristics such as the discharge coefficient of circular-crested weir and the flow velocity and pressure distribution of weir crest. The simulation results well reproduced the overflow characteristics of the overfall of circular-crested weir both qualitatively and quantitatively. As for the discharge coefficient, rational results were yielded by the discharge coefficient equation proposed by Hager(1985) in the $H_1/R_b<0.58$ and by the discharge coefficient equation proposed by Samani and Bagheri(2014) in the $H_1/R_b>0.58$, respectively. Because most existing discharge coefficient equations were developed by disregarding the effects of the approach velocity, when they are applied, it is necessary to evaluate the effects of the approach velocity on the overflow head beforehand.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.12 no.4
• /
• pp.273-278
• /
• 2009

Overtopping Wave Energy Convertor (OWEC) is an offshore wave energy convertor for collecting the overtopping waves and converting the water pressure head into electric power through the hydro turbines installed in the vertical duct which is fixed in the sea bed. The numerical wave tank based on the commercial computational fluid dynamics code Fluent is established for the corresponding analysis. Several incident wave conditions and shape parameters of the overtopping device are calculated. The straight line type and parabolic type of the sloping arm are compared in the optimal designing investigation of the overtopping characteristics and discharge for OWEC device. The numerical results demonstrate that the parabolic sloping arm is available for wave running up and the overtopping discharge increasing.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2020.06a
• /
• pp.26-26
• /
• 2020

하천수의 수심을 유지하기 위하여 설치된 콘크리트 취수보 대신 강자갈이나 쇄석을 채움재로 하는 돌망태를 사용하게 되면 토사퇴적으로 인한 건천화나 상, 하류 수생태계 단절과 같은 문제를 어느 정도 감소시킬 수 있을 뿐만 아니라, 자갈접촉산화작용에 의한 수질개선과 공사비 절감 효과 등의 장점이 있다. 그러나 돌망태는 투수성이므로 불투수성인 콘크리트 보다 저류측면에서 불리하다. 콘크리트 취수보에서의 흐름은 보 정점의 형상, 보의 폭, 높이, 그리고 월류수심에 좌우되며, 베르누이 방정식과 연속방정식에 의해 방류량 산정식을 유도하고, 유량계수와 같은 실험상수를 결정하여 방류량을 계산한다. 돌망태 취수보의 흐름은 보의 높이, 보의 길이, 보의 상류수심 외에 채움재의 형상, 입경, 배치상태가 흐름에 영향을 미친다. 따라서 콘크리트 취수보에 적용되었던 기존의 방류량 산정식을 그대로 적용할 수 없다. 돌망태 보의 통과류는 실험상수가 포함된 비선형 수두손실방정식으로 표현할 수 있다. 실험상수는 비표면적의 크기를 의미하는 채움재의 평균동수반경와 관계되며, 평균동수반경은 채움재 입자의 형상으로 부터 구할 수 있다. 따라서 실험을 통하여 채움재 입자의 형상과 크기에 따른 실험상수와 평균동수반경의 관계를 구하면 비선형 수두손실방정식으로부터 통과류의 방류량을 계산할 수 있게 된다. 본 연구는 돌망태 취수보가 대수층함양 원수 공급시설물로서 타당한가를 평가하기 위하여 수행되었다. 콘크리트 취수보의 월류량 계산은 기존의 방류량 산정식을 이용하였으며, 돌망태 취수보는 실험상수와 평균동수반경의 기존관계식을 이용하여 통과류의 방류량을 계산하였다. 이와 같이 계산된 각각의 수심-방류량 관계로 부터 수심을 비교하였다. 동일한 유량조건에서 돌망태 취수보의 상류수심은 콘크리트 취수보보다 작게 계산되었다. 상류수심은 돌망태 채움재 입자의 크기가 작을수록 증가하여, 돌망태 취수보는 채움재의 입자크기가 작을수록 저류성능이 개선됨을 알 수 있었다. 따라서 돌망태 취수보는 채움재의 입경이 작을수록 콘크리트 취수보의 저류수준에 접근할 수 있을 것으로 판단되었다.

• Journal of Korea Water Resources Association
• /
• v.47 no.11
• /
• pp.1007-1015
• /
• 2014

This study investigates the discharge coefficient of Improved-Pneumatic-Movable (IPM) weir through the weir, a kind of movable weirs, to estimate much more accurate rating curves using laboratory flume experiments. The discharge coefficient ($C_d$) is from 0.613 to 0.634 by the stand-up angle of the weir. The upstream Froude Number ($F_{r1}$), relative crest length(${\xi}$), Headwater Ratio ($H_1/W$), the Overflow depth ratio of weir crest ($y_c/y_1$) was changed by the upstream. And the downstream Froude number ($F_{r2}$), the Overflow depth ratio of weir crest and Downstream Water depth ($y_c/y_2$) was changed by the downstream. The ratio of Downstream and Up and Downstream water Depth (${\Delta}y/y_2$) was found to be changed by both of the up and downstream flow. They considered the major influence variables and derived the Discharge coefficient Formula at this study. The Discharge coefficient of the Improved-Pneumatic-Movable (IPM) weir was settled by the height of the Movable weir, that is to say, it was settled by the flow conditions of upstream approach flow head and physical data according to the standing angle.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.524-529
• /
• 2006

실제유량에 대한 이론유량의 비로 정의되는 유량계수는 수공구조물의 설계에 있어서 중요한 요소 중에 하나이다. 댐 여수로 또한 이러한 유량계수를 통하여 산정되는 방류량에 따라 여수로 월류부의 규모가 결정되며 이러한 수위별 방류량 산정에 있어서 유량계수는 $\ulcorner$댐 설계기준$\lrcorner$에 제시되어 있는 미국 개척국(USBR)의 여러 경험을 통하여 산정한 유량계수 그래프에서 독치하여 결정한다. 본 연구에서는 국내 댐 여수로의 설계 유량계수를 수리모형실험 및 수치해석을 통하여 비교.검토하였으며, 이에 대한 적정 유량계수의 범위를 산정하였다. 이러한 유량계수의 범위를 기 건설 운영 중인 댐의 관측자료를 통하여 그 적정성을 검토하였고, 그 결과 상당수의 자료가 금회 산정한 유량계수 적정 범위 이내에 드는 것으로 나타나 국내 댐 여수로 유량계수는 적정한 것으로 검토되었다.

• Journal of Korea Water Resources Association
• /
• v.41 no.1
• /
• pp.65-74
• /
• 2008

The small and medium sized dams have the fill dam type of a lot of occasions, which are often weak in cases of major floods. For this reason, although a countermeasure is in great need, due to the importance of the facilities and financial situations, no direct safety measures have been taken. In this study, in order to minimize construction expenditure for practical safety measures in cases of major floods, the overflow section of spillway has been analyzed focusing on how the overflow capacity will increase in the case of partially rebuilding a part of the overflow section of spillway favorable for hydraulic conditions. The Labyrinth weir and movable weir was chosen for reconstruction models of the overflow section. Moreover, for analyzing the after-effects of the reconstruction, a small scale dam was temporarily chosen for various experiments such as the hydraulic model testing and the three dimension numerical evaluation through the use of Flow-3D.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.22 no.2
• /
• pp.67-72
• /
• 2010

In this study, the impact on the circulating water system has been analyzed due to an installation of helical turbine to develop hydro-kinetic energy at the discharge channel of the power plant. Numerical simulations of velocity and pressure variations have been performed when one set of $3.6\;m\;{\times}\;1.5\;m$ sized helical turbine is installed at the outlet of discharge culvert. In case of mean sea level, change of downstream water surface elevation does not affect upstream elevation of the weir because its propagation is blocked by the seal well weir. However in case of highest high water level, change of downstream elevation affects upstream elevation because flow pattern in discharge culvert becomes the full pipe flow with submerged weir. Although an unstable pressure change occurs in upstream of the weir during the intial 10 minutes after beginning of the discharge, it becomes stable after that time. In addition, a rise of water surface elevation by 0.2 m is observed but it is concluded that it hardly affects the safety of circulating water pump (CWP) although its required power is increased more or less. Therefore, the increase of required power of CWP needs to be considered for evaluation of the helical turbine applicability.