하류하천의 영향 최소화를 위한 보조 여수로 최적 활용방안 검토

유형주(Hyung Ju Yoo),주성식(Sung Sik Joo),권범재(Beom Jae Kwon),이승오(Seung Oh Lee) 한국방재안전학회 2021 한국방재안전학회 논문집 Vol.14 No.2

최근 기후변화로 인해 강우강도 및 빈도의 증가에 따른 집중호우의 영향 및 기존 여수로의 노후화에 대비하여 홍수 시 하류 하천의 영향을 최소화할 수 있는 보조 여수로 활용방안 구축이 필요한 실정이다. 이를 위해, 수리모형 실험 및 수치모형 실험을 통하여 보조 여수로 운영에 따른 흐름특성 변화 검토에 관한 연구가 많이 진행되어 왔다. 그러나 대부분의 연구는 여수로에서의 흐름특성 및 기능성에 대한 검토를 수행하였을 뿐 보조 여수로의 활용방안에 따른 하류하천 영향 검토 및 호안 안정성 검토에 관한 연구는 미비한 실정이다. 이에 본 연구에서는 기존 여수로 및 보조 여수로 방류 조건에 따른 하류영향 분석 및 호안 안정성 측면에서 최적 방류 시나리오 검토를 3차원 수치모형인 FLOW-3D를 사용하여 검토하였다. 또한 FLOW-3D 수치모의 수행을 통한 유속, 수위 결과와 소류력 산정 결과를 호안 설계허용 기준과 비교하였다. 수문 완전 개도 조건으로 가정하고 계획홍수량 유입 시 다양한 보조 여수로 활용방안에 대하여 수치모의를 수행한 결과, 보조 여수로 단독 운영 시 기존 여수로 단독운영에 비하여 최대유속 및 최대 수위의 감소효과를 확인하였다. 다만 계획홍수량의 45% 이하 방류 조건에서 대안부의 호안 안정성을 확보하였고 해당 방류량 초과 경우에는 처오름 현상이 발생하여 월류에 대한 위험성 증가를 확인하였다. 따라서 기존 여수로와의 동시 운영 방안 도출이 중요하다고 판단하였다. 여수로의 배분 비율 및 총 허용 방류량에 대하여 검토한 결과 보조 여수로의 방류량이 기존 여수로의 방류량보다 큰 경우 하류하천의 흐름이 중심으로 집중되어 대안부의 유속 저감 및 수위 감소를 확인하였고, 계획 홍수량의 77% 이하의 조건에서 호안의 허용 유속 및 허용 소류력 조건을 만족하였다. 이를 통하여 본 연구에서 제안한 보조 여수로 활용방안으로는 기존 여수로와 동시 운영 시 총 방류량에 대하여 보조 여수로의 배분량이 기존 여수로의 배분량보다 크게 설정하는 것이 하류하천의 영향을 최소화 할 수 있는 것으로 나타났다. 그러나 본 연구는 여수로 방류에 따른 대안부에서의 영향에 대해서만 검토하였고 수문 전면 개도 조건에서 검토하였다는 한계점은 분명히 있다. 이에 향후에는 다양한 수문 개도 조건 및 방류 시나리오를 적용 및 검토한다면 보다 효율적이고, 효과적인 보조 여수로 활용방안을 도출이 가능할 것으로 기대 된다. Recently, as the occurrence frequency of sudden floods due to climate change increased and the aging of the existing spillway, it is necessary to establish a plan to utilize an auxiliary spillway to minimize the flood damage of downstream rivers. Most studies have been conducted on the review of flow characteristics according to the operation of auxiliary spillway through the hydraulic experiments and numerical modeling. However, the studies on examination of flood damage in the downstream rivers and the stability of the revetment according to the operation of the auxiliary spillway were relatively insufficient in the literature. In this study, the stability of the revetment on the downstream river according to the outflow conditions of the existing and auxiliary spillway was examined by using 3D numerical model, FLOW-3D. The velocity, water surface elevation and shear stress results of FLOW-3D were compared with the permissible velocity and shear stress of design criteria. It was assumed the sluice gate was fully opened. As a result of numerical simulations of various auxiliary spillway operations during flood season, the single operation of the auxiliary spillway showed the reduction effect of maximum velocity and the water surface elevation compared with the single operation of the existing spillway. The stability of the revetment on downstream was satisfied under the condition of outflow less than 45% of the design flood discharge. However, the potential overtopping damage was confirmed in the case of exceeding the 45% of the design flood discharge. Therefore, the simultaneous operation with the existing spillway was important to ensure the stability on design flood discharge condition. As a result of examining the allocation ratio and the total allowable outflow, the reduction effect of maximum velocity was confirmed on the condition, where the amount of outflow on auxiliary spillway was more than that on existing spillway. It is because the flow of downstream rivers was concentrated in the center due to the outflow of existing spillway. The permissible velocity and shear stress were satisfied under the condition of less than 77% of the design flood discharge with simultaneous operation. It was found that the flood damage of downstream rivers can be minimized by setting the amount allocated to the auxiliary spillway to be larger than the amount allocated to the existing spillway for the total outflow with simultaneous operation condition. However, this study only reviewed the flow characteristics around the revetment according to the outflow of spillway under the full opening of the sluice gate condition. Therefore, the various sluice opening conditions and outflow scenarios will be asked to derive more efficient utilization of the auxiliary spillway in th future.

Investigation of Energy Dissipation Rate of Stepped Vertical Overfall (SVO) Spillway Using Physical Modeling and Soft Computing Techniques

Saman Baharvand,Reza Rezaei,Nasser Talebbeydokhti,Roohollah Nasiri,Seyed Mehrab Amiri 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.12

In the present study a physical model of a stepped vertical overfall (SVO) spillway is proposed and designed as a novel combination of a free overfall spillway with horizontal steps. First, the hydraulic design characteristics of the proposed spillway were discussed using a laboratory-scaled model. Effective parameters on the energy dissipation rate were defined as the relative critical depth, Froude number, number of steps, and dimensionless steps’ geometry parameter using dimensional analysis. The energy dissipation rate of the stepped vertical overfall spillway is measured using a waterwheel laboratory setup. Different geometry and hydraulic scenarios were used to assess the energy dissipation rate variation of the proposed spillway. Furthermore, Support Vector Regression and Random Forest Regression methods were used to estimate the energy dissipation of the proposed structure. Investigating the energy dissipation rate of 27 geometry scenarios with the available range of discharge revealed that the energy dissipation rate against the water’s relative depth inside the SVO spillway follows a gradually increasing trend ranging between 88.53% to 98.06%. Also, random forest regression algorithm showed more accurate prediction performance than support vector regression approach with RMSE = 0.128 and R2 = 0.99 in training stage and RMSE = 0.115 and R2 = 0.99 in testing stage. The support vector regression model estimated the proposed spillway’s energy dissipation rate with an accuracy of RMSE = 0.67 and R2 = 0.88 in training stage and RMSE = 0.61 and R2 = 0.9 in testing stage.

Effect of Barrier Height on the Design of Stepped Spillway using Smoothed Particle Hydrodynamics and Particle Image Velocimetry

Aqil Azman,Fei Chong Ng,Mohd. Hafiz Zawawi,Aizat Abas,Mohd. Remy Rozainy M. A. Z.,Ismail Abustan,Mohd. Nordin Adlan,Wei Loon Tam 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.2

Three-dimensional stepped spillway problems are simulated numerically using smoothed particle hydrodynamics (SPH) to visualize the flow of water along the steps and its flow dynamics. In particular, two distinct scaled-down stepped spillway models were studied with each having barrier heights of 10 mm and 25 mm, respectively. The impact of varying the height of the barrier in the design of the stepped spillway is studied in terms of it flow pattern, flow dynamics, aeration efficiency and oxygenation performances. State-of-the-art particle image velocimetry (PIV) experiment was carried out to affirm the validity of SPH findings and it turns out that both the water flow patterns attained in the SPH and PIV are quantitatively comparable. Further quantitative analysis revealed that the flow velocities in both methodologies are in great consensus. Conclusively, this has demonstrated that the capability and reliability of SPH to precisely approximate the water using finite set of particles to model the flow along the stepped spillway. Both stepped spillway configurations show nappe flow regime as the water descends down the steps. Nonetheless, vigorous hydraulic jump phenomena that is associates with the formation of turbulence and vortices is prominently observed in the configuration with larger barrier height. Decisive SPH data obtained concluded that as the barrier height increases from 10 mm to 25 mm, the water flows down the steps faster at lower pressure value and the overall aeration efficiency is improved from 1.1% to 1.2%. The usage of the higher barrier would promote the occurrence of substantial air entrainment during water swirling that will increase the power dissipation in flow. Subsequently, this while lower the power drawn to achieve the desired aeration effect. Ultimately, this study has justified the critical influence of barrier height dimension on the stepped spillway flow behavior and aeration performance.

Evaluation of Cavitation Occurrence Based on Reliability in Chute Spillways by Using First Order Reliable Method and Monte Carlo Simulation Method from 18 Spillways Laboratory Models, Iran

Mehdi Azhdary Moghaddam,Amin Hasanalipour Shahrabadi 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.4

Controlling cavitation occurrence is one of the most important factors in chute spillways designing due to high velocity and the negative pressure of flow. A probabilistic design approach was implemented in the present study to estimate the probability of cavitation occurrence on chute spillways. In addition, the uncertainty presence of the effective parameters in the limit state function related to the cavitation occurrence was highlighted in the present design. The probability of cavitation occurrence was studied based on the reliability of first order reliable method (FORM) and it was controlled by Monte Carlo simulation method. The data was extracted from eighteen spillways laboratory models built by the Iranian Water Research Institute, among which ten were aerated and eight were without aerator. Accordingly, as a result of the performance of these spillways and the cavitation occurrence in the prototype, a graph and its relationship was found for controlling the cavitation occurrence and its failure probability based on the mean velocity and flow mean pressure along the chute spillway. According to the results of this study as a new method for designing based on reliability, it could be controlled the probability of cavitation occurrence.

Experimental Investigation of the Hydraulic Performance of a Hydraulic-Jump-Stepped Spillway

Yu Zhou,Jianhua Wu,Fei Ma,Shangtuo Qian 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.10

For a traditional stepped spillway, low energy dissipation and cavitation damage may occur when the unit discharge is larger than a limit due to reduced air entrainment in the flow. In the present work, a new type of stepped spillway called hydraulic-jump-stepped spillway (HJSS) was developed, and the air was efficiently entrained into the flow by means of a hydraulic jump in the aeration basin, which was an aeration element of this stepped spillway. Compared with the traditional stepped spillway, various aspects of the hydraulic performance of the HJSS were experimentally investigated, including the flow pattern, energy dissipation, air entrainment characteristics and time-averaged pressure. Physical model results demonstrated that the HJSS achieved a higher energy dissipation, a more favorable air entrainment performance, and a more reasonable pressure distribution. The HJSS successfully increased the unit discharge from 50 – 60 m2/s for a traditional stepped spillway to 101.47 m2/s.

Experimental and computational study on flow over stepped spillway

Bhaskar Jyoti Medhi,Anugrah Singh,Ashish Kumar Thokchom,Sadhan Mahapatra 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5

The flow over a stepped spillway has complex nature, and its characteristics are remarkably different from other kinds of spillways. This study conducts experimental investigations and numerical simulations on the flow behavior (velocity, concentration profile) and macroscopic features (interface position and self-aeration) of water and neutrally buoyant suspension of non-colloidal particles in a stepped spillway with uniform steps. The development of nappe, transition, and skimming flow regimes is experimentally investigated by using a flow visualization technique. The inception point related to air entrainments is identified in the experimental study. The inception point usually moves downstream and increases the length of the non-aerated region with the increase of flow rate. Results of numerical and experimental studies indicate that a vortex is formed in the triangular cavity below the pseudo-bottom line (imaginary line joining two adjacent step edges) in the stepped channel. This vortex rotates in a clockwise direction for a short time period and returns to the main flow to move downward in the channel. The velocity vector map from numerical simulation predicts the maximum velocity in the middle portion of the spillway, that is, near the pseudo-bottom line. A volume of fluid model coupled with a standard k–e turbulence model is used in the CFD simulations to predict the location of the air–water air-suspension interface. The results are compared with experimental measurements. The calculated interface position agrees well with the experimental measurements. The migration and transport of particles are evaluated based on a diffusive flux model of shear induced particle migration. The contour map for velocity and particle concentration shows a remarkable increase in particle concentration near the air-suspension interface.

저수지 월류 시 여수토 접속부 세굴에 따른 붕괴 현상의 실험적 연구

김영익,연규석,김기성,정종우,김용성,Kim, Young-Ik,Yeon, Kyu-Seok,Kim, Ki-Sung,Jeong, Jong-Woo,Kim, Yong-Seong 한국농공학회 2011 한국농공학회논문집 Vol.53 No.2

This study is a preliminary investigation into the development of a construction method that will protect a reservoir even during over flows caused by severe flooding. Through hydraulic modeling tests, the destructive phenomena caused by spillway-junction scour during reservoir overflow were modeled, and the effects on the embankment during such an overflow and the spillway-junction movements are discussed. The reservoir destruction model used the Tanbu reservoir, located in Gangwondo Chuncheon-si Namsanmyeon (H=22 m, L=115 m), as the model reservoir and created an embankment with a 1/60 ratio. We review the spillway-junction safety factor during overflow and embankment movement following reinforcement measures for three different cases: no reinforcement, cemented sand and gravel (CSG) reinforcement and water-blocking sheet reinforcement. The results of this study confirmed that when the spillway-junction is exposed to soil, it is very vulnerable to overflow and that a water-blocking sheet or CSG reinforcement are very effective measures in preventing embankment destruction in the long-term period.

여수로 방류에 따른 여수로 바닥슬래브의 손상 발생원인 수치모의 검토

유형주,신동훈,김동현,이승오 한국방재안전학회 2021 한국방재안전학회 논문집 Vol.14 No.4

Recently, as the occurrence frequency of sudden floods due to climate variability increased, the damage of aging chuteway slabs of spillway are on the rise. Accordingly, a wide array of field survey, hydraulic experiment and numerical simulation have been conducted to find the cause of damage on chuteway slabs. However, these studies generally reviewed the flow characteristics and distribution of pressure on chuteway slabs. Therefore the derivation of damage on chuteway slabs was relatively insufficient in the literature. In this study, the cavitation erosion and hydraulic jacking were assumed to be the causes of damage on chuteway slabs, and the phenomena were reproduced using 3D numerical models, FLOW-3D and COMSOL Multiphysics. In addition, the cavitation index was calculated and the von Mises stress by uplift pressure distribution was compared with tensile and bending strength of concrete to evaluate the possibility of cavitation erosion and hydraulic jacking. As a result of numerical simulation on cavitation erosion and hydraulic jacking under various flow conditions with complete opening gate, the cavitation index in the downstream of spillway was less than 0.3, and the von Mises stress on concrete was 4.6 to 5.0 MPa. When von Mises stress was compared with tensile and bending strength of concrete, the fatigue failure caused by continuous pressure fluctuation occurred on chuteway slabs . Therefore, the cavitation erosion and hydraulic jacking caused by high speed flow were one of the main causes of damage to the chuteway slabs in spillway. However, this study has limitations in that the various shape conditions of damage(cavity and crack) and flow conditions were not considered and Fluid-Structure Interaction (FSI) was not simulated. If these limitations are supplemented and reviewed, it is expected to derive more efficient utilization of the maintenance plan on spillway in the future. 최근 기후변동성으로 인하여 집중호우의 발생빈도 및 강우강도 증가로 노후화된 여수로 바닥슬래브 표면에서의 손상이 발생하여 잦은 보수·보강이 필요한 실정이다. 이를 위해 현장조사, 수리모형 실험 및 수치모형 실험을 통하여 여수로 방류에 따른 손상발생 원인검토에 관한 연구가 많이 진행되어 왔다. 그러나 대부분의 연구는 일반적으로 여수로의 흐름특성 및 압력분포에 대한 검토를 수행하였을 뿐 손상의 근본적인 발생원인 규명에 관한 연구는 미비한 실정이다. 이에 본 연구에서는 여수로 바닥슬래브 손상발생 원인을 도출하기 위해 공동침식 및 수력잭킹(hydraulic jacking)으로 인한 콘크리트 탈락관점에서 3차원 수치모형인 FLOW-3D와 COMSOL Multiphysics를 사용하여 검토하였다. 또한 공동지수를 산정하고 압력분포로 인하여 구조물이 받는 응력과 콘크리트의 인장·굽힘강도를 비교하여 공동침식 및 수력잭킹으로 인한 콘크리트 탈락 발생 가능성을 확인하였다. 수문 완전개도 조건에서 여수로 방류에 따른 공동침식 및 수력잭킹에 대하여 수치모의를 수행한 결과, 여수로 하류부에서 공동지수가 0.3 미만으로 공동침식 발생 가능성을 확인하였고, 공동부 및 균열부에서 압력분포에 따라 콘크리트가 받는 응력은 4.6~5.0 MPa로 콘크리트 인장강도와 굽힘강도와 비교를통하여 지속적인 압력변동으로 인한 콘크리트의 피로파괴 또는 휨파괴 가능성을 확인하였다. 따라서 여수로 고유속 흐름에 의한 공동현상 및 수력잭킹이 여수로 바닥슬래브 손상발생의 다양한 원인 중 하나로 판단하였다. 그러나 본 연구는 다양한 형상 조건 및 방류 시나리오를 적용하고 유체-구조물 상호작용(Fluid-Structure Interaction, FSI)모의를 수행하지 못하였다는 한계점이 있다. 이에 향후에는한계점을 보완하여 검토한다면 보다 효율적이고 효과적인 여수로 유지관리 방안 도출이 가능할 것으로 기대한다.

부항댐 방류량에 따른 복합 여수로 수리모형실험

김동주 ( Kim Dong Joo ),송현구 ( Song Hyun Gu ),박창규 ( Park Chang Kyu ) 한국농공학회 2006 한국농공학회 학술대회초록집 Vol.2006 No.-

The complex spillway is being planned for Bu-hang, in order to enhance the safety against frequent disastrous floods. To analyze hydraulic characteristics for various flow conditions at some main parts on the spillway, a scale-down hydraulic model was made and experimented in KRC. Several flow characteristics were improved by some modifications of the planning on the spillway.

임하댐 터널식 여수로 계획에 따른 수리모형 실험

송현구 ( Song Hyun Gu ),박창언 ( Park Chang Eon ),김동주 ( Kim Dong Joo ),김형일 ( Kim Hyung Il ) 한국농공학회 2006 한국농공학회 학술대회초록집 Vol.2006 No.-

The tunnel-type spillway is being planned for Imha-Dam, in order to enhance the safety against frequent disastrous floods. To analyze hydraulic characteristics for various flow conditions at some main parts on the spillway, a scale-down hydraulic model was made and experimented in KRC. Several flow characteristics were improved by some modifications of the planning on the spillway.