Proceedings of the 9th International Conference

on Hydrodynamics (ICHD 2010)

October 11 – 15, 2010,Shanghai, China
Editors: Y. S. Wu, S. Q. Dai, H. Liu, L. D. Zhou, X. C. Yang

Hydraulic Engineering and Water Conservancy (12)

G1-1 Reduction of local scour at a bridge pier fitted with a collar in a 180 degree flume bend (Case study: oblong pier)

Alireza Masjedi , Mahmood Shafaei Bejestan , Abdolkarim Esfandi

Islamic Azad University Ahwaz Branch, Ahwaz, Iran

Abstract :

Local scouring around the bridges pier occurs because of flow separation and developing several vortexes around the bridge pier. Such scour hole can cause failure of the bridge especially during the river floods. In this study, the use of oblong collars for reducing the effects of local scour at a bridge pier is presented together with the time aspect of the scour development. The study was conducted using in a 180 degree laboratory flume bend. Tests were conducted using one oblong pier in positions of 60degree under one flow conditions. In this study, the time development of the local scour around the oblong pier fitted with and without collar plates was studied. The effects of various sizes of collars fitted on the temporal development of scour depth at the oblong pier were also studied. The time development of the scour hole around the model pier with and without a collar installed was compared with similar studies on bridge piers. The results of the model study indicated that the maximum depth of scour is highly dependent on the experimental duration. It was observed that, as the size of a collar plate increases, the scour decreases. So minimum depth of scour is dependent on the 3D collar.

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G1-2 Study on external water pressure of water conveyance tunnel for the pumped storage power stations in Huizhou City

Yong Huang, Zhi-fang Zhou

Department of Earth Science and Engineering, Hohai University, Nanjing, China

Abstract :

A 3D numerical model of groundwater flow is established according to the geological conditions. Fractured rock mass is consist of rocks matrix, which is represented using the equivalent continuum model and fracture network, which is described with a discrete-fractured network model. The two models are coupled with continuum groundwater table and flux equilibrium, and solution of coupling model is deducted. The comparison is conducted between the measured and simulated external water pressure, which shows that the coupled model is feasible. Also different drainage schemes are designed and discuss the distribution of external water pressure of the schemes.

G1-3 Analysis of influence factors of cavity length in the spillway  tunnel downstream of middle gate chamber outlet with sudden lateral enlargement and vertical drop aerator

Xu-dong Ma, Guang-qing Dai, Qing Yang, Guo-jing Li, Lei-lei Zhao

Stat Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chendu , China

Abstract :

For the aerator of sudden lateral enlargement and vertical drop at the outlet of middle chamber is taken as research object by the method of turbulent numerical simulation which is used to study the cavity length of spillway tunnel downstream of chamber. And there is reasonably good agreement between the numerical simulation and model tests results. The results show that, the distribution of adhesion spots along side wall varies according to the changing of aerator geometric dimension; changes of drop height or enlargement width have effect on both lateral and bottom cavity length; the bottom cavity length correlates closely to drop height and lateral cavity length has the most remarkable effect on enlargement width; under the same shape, both the lateral and bottom cavity grows longer with Froude number increasing, and the bottom cavity grows rapidly.

G1-4 A mechanical energy losses comparison in inclined hydraulic jumps over a thin wall and a step

J D Demetriou , D J Dimitriou

National Technical   Univ. of Athens, Greece

Abstract :

In this study, based on experimental evidence, the mechanical energy losses (ΔΗ) along two hydraulic inclined (angle φ, 0o ≤φ≤8o) jumps (d1, dm), namely the jump over a thin wall   (w) and the jump over an abrupt step (w), are examined, compared and discussed, in the forms of ΔΗ/d1 and ΔΗ/H1, for a common field of w/d1and angles φ. Two empirical equations for ΔΗ/d1are presented and a number of diagrams as well, showing the differences in corresponding energy dissipation. The results of this investigation may help the hydraulic engineer when designing pertinent structures along open channel works.

G1-5 Comparison of wave fields caused by four proposed beach nourishment schemes in Beidaihe, China

Cui-ping Kuang, Lu-lu He, Yu Zhang, Yi Pan, Shu-gang Liu

Department of Hydraulic Engineering, College of Civil Engineering, Tongji University, Shanghai, China

Abstract :

The erosion of west beach in Beidaihe has become severe in the recent years. In order to nourish the beach, four different engineering nourishment schemes are proposed. As a near shore project, wave is the main force in the sea area of west beach. Based on the information above, wave fields in the sea area of west beach under both ordinary wave condition (S, Hs=0.7m, T=3.2s) and strong wave condition (NE, Hs=1.5m, T=4.7s) are analyzed. The resultshows that beach nourishment with two jetties and three submerged breakwaters protects the west beach most effectively.

G1-6 Investigation of air-core vortex at hydraulic intakes

Ying-kui Wang, Chun-bo Jiang, Dong-fang Liang

State key laboratory of Hydroscience and Engineering, Tsinghua University, Beijing , China

Abstract :

Hydrodynamic properties of the surface vortex have been investigated. Based on the Navier-Stokes equations, three sets of the new formulations for the tangential velocity distributions are derived, and verified against the experimental measurements in the literature. It is shown that one modification greatly improves the agreement with the experimental data. Physical model experiments were carried out to study the intake vortex related to the Xiluodu hydropower project. The velocity fields were measured using the Particle Tracking Velocimetry (PTV) technique. The proposed equation for tangential velocity distribution is applied to the Xiluodu project with the solid boundary being considered by the method of images. Good agreement has been observed between the formula prediction and the experimental observation.

G2-1 Flow resistance in steep mountain rivers in Bolivia

Mauricio Romero, Nelson Revollo, Johnny Molina

Hydraulics Laboratory; Faculty of Science and Technology,San Simon University, Cochabamba, Bolivia

Abstract :

The present paper illustrates the assessment of the Darcy-Weisbach flow resistance coefficients fat five steep mountain rivers located in the northern mountain range surrounding the city of Cochabamba in Bolivia. Extensive field works were carried out. Several empirical formulas were tested. Results show that some of the aforementioned formulas provide good results in the assessment of f, being the model of Ugarte & Madrid-Aris (1994) the most accurate one. Plots showing direct logarithmic relationships between f and the riverbed slope So were obtained for each studied river, as well as an overall relationship of f vs. So.

G2-2 Simulation of storm surge for whole Pearl River Estuary with upriver runoff

Yun Bao, Hong-yue Zou, Jie-bing Liu

Hydraulics Laboratory; Faculty of Science and Technology,San Simon University, Cochabamba, Bolivia

Abstract :

In this paper, the typhoon wind field is given by the Typhoon model. The simulation for the Pearl River estuary is nested with storm surge filed in the northern South China Sea. Using the two-dimensional hydrodynamic model ccost, the simulation model of the storm surge which considers the upriver runoff is established with the structured grid of the whole Pearl River estuary region. The landing process of the 0814 and 0915 typhoon which has great impact in the Pearl River Delta region in the recent years was simulated, and the comparison between the result of simulation and measured water level was given. It show that the storm surge model for the whole Pearl River estuary with the upriver runoff can better simulate the impact of storm surges in the whole Delta. The two huge eddies caused by the strong winds can be seen in the flow field of the Lingding estuary during the typhoon landing.

G2-3 Swimming behavior of isolated ayu, plecoglossus altivelis altivelis, in running water

Kouki Onitsuka , Juichiro Akiyama , Hikaru Takeuchi, Atsushi Ono

Hydraulics Laboratory; Faculty of Science and Technology,San Simon University, Cochabamba, Bolivia.

Abstract :

Swimming behavior of isolated fish in running water has not been investigated. In this study, the swimming behavior of isolated ayu in the running water was recorded with a digital video camera with changing the velocity for five cases. The result showed that the swimming trajectory can be described by nodes and branches. It was found that the ground distance, swimming distance, ground speed  and  swimming speed in the streamwise direction increases with an increase of the flow velocity, because the ayu has positive rheotaxis. The turning angle of swimming trajectory decreases with an increase of the flow velocity.

G2-4 Comparison of wave fields caused by four proposed beach nourishment schemes in Beidaihe, China

Cui-ping Kuang,Lu-lu He, Yu Zhang, Yi Pan, Shu-gang Liu

Department of Hydraulic Engineering, College of Civil Engineering, Tongji University, Shanghai, China

Abstract :

The erosion of west beach in Beidaihe has become severe in the recent years. In order to nourish the beach, four different engineering nourishment schemes are proposed. As a near shore project, wave is the main force in the sea area of west beach. Based on the information above, wave fields in the sea area of west beach under both ordinary wave condition (S, Hs=0.7m, T=3.2s) and strong wave condition (NE, Hs=1.5m, T=4.7s) are analyzed. The result shows that beach nourishment with two jetties and three submerged breakwaters protects the west beach most effectively.

G2-5 Hydraulics of discharge tunnel service gate: the flow regimes

A. Mohagheg, Jian-hua Wu

College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing , China

Abstract :

During experiments which were conducted on a discharge tunnel laboratory model, bottom cavity beneath the free-falling nappe immediate downstream of the service gate was focused on. Three different flow regimes were detected each of which with particular features. The results provide a fair characterization of each flow regime. They highlight some differences between the limits of flow regimes in terms of dimensionless bottom cavity length and Froude number values under various step heights. The results also demonstrate that increase in step height at service gate provides more aeration in lower range of flow rates.

G2-6 Computational models for analyzing scouring problems at Nile River

Maged M. Elfiky , Abdelazim M. Negm , Talaat M. Owais, M. A Nassar

Water & Water Structures Engineering Dept., Faculty of Engineering, Zagazig University, Zagazig, Egypt

Abstract :

A computational model was used to estimate and analyze scouring problems at the Nile River. A partial failure of the upper slab of the lock guide pier upstream of the new Esmaeilia canal intake was observed. Therefore, the reach upstream of the new Esmaelilia canal 920 m long on the Nile River in front of Esmaeilia canal intake is considered in this paper. The hydrodynamic process has been calculated using a 2-D hydrodynamic model (HYD-2), which simulates the flow behavior in rivers. The sediment transport in the reach was simulated using a 2-D sediment transport model which has the capability of predicting the locations of scouring and silting along the considered reach. The use of the models was illustrated through the use of two alternatives solution to the problem.