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Fin characteristics of aerator devices with lateral deflectors

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Journal of Hydrodynamics 2013年第2期25卷 258-263页

作者：吴建华李丹马飞钱尚托 College of water conservancy and Hydropower Engineering Hohai University

The fins will be formed if the lateral deflectors in the side-walls with a bottom aerator device are improperly designed, and the flow regime downstream of the aerator device will be worsened. In this paper, the height and the length of the fins induced by the lateral deflectors are theoretically analyzed along with their influencing factors, and the fin characteristics are experimentally investigated on the basis of the theoretical analysis. It is shown that the intensities of the fins are strongly dependent on the ratio of the lateral cavity length to the bottom cavity length, and other factors, like the working head, the height and the angle of the lateral deflector, the flow Froude number around the aerator device, affect the fins indirectly through the changes of the lateral cavity length. When an aerator device with lateral deflectors is designed, it is crucial to match the above mentioned ratio, and to make the ratio of the two cavity lengths less than 1.0 in order to avoid the generation of the fins.

关键词： aerator cavity length fin lateral deflector

Inception point of air entrainment over stepped spillways

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Journal of Hydrodynamics 2013年第1期25卷 91-96页

作者： WU Jian-hua ZHANG Bin MA Fei College of water conservancy and Hydropower Engineering Hohai University

The location of the inception point of the air entrainment directly affects the energy dissipation ratio, the cavitation damage control, and the training wall height designs for a stepped spillway and a stilling basin. In this paper, the boundary layer theory of plates is used to predict the location of the inception point of the air entrainment over the stepped spillways by assuming the steps on the spillways as a kind of roughness. An empirical formula is pres.nted based on the physical model experiments, with the maximum error less than 1% except at one point where the error is 1.6%, as compared to the experimental data. Meanwhile, it is shown that the location of the inception point of the air entrainment for the stepped spillway is much nearer to the top of the spillway than that for a smooth spillways, which explains why the high ratio of the energy dissipation is provided for the stepped spillway.

关键词： air entrainment cavitation energy dissipation inception point stepped spillway unit discharge

Influence of bending rigidity of submerged vegetation on local flow res.stance

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Journal of Hydrodynamics 2014年第2期26卷 242-249页

作者：吴龙华杨校礼 College of water conservancy and Hydropower Engineering Hohai University

The different state of the submerged vegetation has different influences on the flow res.stance. This paper explores.the relationship between the state and the res.stance of an individual submerged vegetation, and the relative bending rigidity of the submerged vegetation is determined by the state of the submerged vegetation. Based on the experimental observations, the state and the res.stance of an individual submerged vegetation are analyzed under different inflow conditions. At the same time, the influences of the various submerged vegetations on the flow res.stance are discussed under the same inflow conditions. Some interes.ing relationships are obtained between the flow res.stance and the relative bending rigidity of the submerged vegetation, and it is shown that the flow res.stance increases with the increase of the relative bending rigidity of the submerged vegetation, and they are positively correlated.

关键词： individual submerged vegetation relative bending rigidity local flow res.stance

Stochastic simulation of fluid flow in porous media by the complex variable expres.ion method

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Journal of Hydrodynamics 2013年第2期25卷 215-225页

作者：宋会彬詹美礼盛金昌罗玉龙 College of water conservancy and Hydropower Engineering Hohai University

A stochastic simulation of fluid flow in porous media using a complex variable expres.ion method （SFCM） is pres.nted in this paper. Hydraulic conductivity is considered as a random variable and is then expres.ed in complex variable form, the real part of which is a deterministic value and the imaginary part is a variable value. The stochastic seepage flow is simulated with the SFCM and is compared with the res.lts calculated with the Monte Carlo stochastic finite element method. In using the Monte Carlo method to simulate the stochastic seepage flow field, the hydraulic conductivity is assumed in three different probability distributions using random sampling method. The obtained seepage flow field is examined through skewness analysis, and the skewed distribution probability density function is given. The head mode value and the head comprehensive standard deviation are used to repres.nt the statistics of calculation res.lts obtained by the Monte Carlo method. The stochastic seepage flow field simulated by the SFCM is confirmed to be similar to that given by the Monte Carlo method from numerical aspects. The range of coefficient of variation of hydraulic conductivity in SFCM is larger than used previously in stochastic seepage flow field simulations, and the computation time is short. The res.lts proved that the SFCM is a convenient calculating method for solving the complex problems.

关键词： seepage flow field complex variable expres.ion method (SFCM) stochastic seepage flow Monte Carlo method skewed distribution

Flow choking over weir flow slit-type flip buckets

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Journal of Hydrodynamics 2015年第6期27卷 907-912页

作者：马飞徐准吴建华 College of water conservancy and Hydropower Engineering Hohai University

The flow choking may occur for weir flow slit-type flip buckets trader common operation conditions. An estimation method is developed through introducing a comprehensive coefficient to determine the approach flow Froude number for the flow choking to occur in those flip buckets. The error of the pres.nt method relative to the experimental data is less than 5%. The res.lts show that, the Froude number for the flow choking to occur is related to the contraction ratio and the contraction angle of the flip buckets. When the flow choking occurs, the upper jet trajectory decreases and the lower one is almost not affected, and the dynamic pres.ures.on the bottom and the sidewalls increase due to the flow profile rising on the flip buckets.

关键词： flow choking jet trajectory dynamic pres.ure slit-type flip bucket weir flow

Hydraulic characteristics of stepped spillway dropshafts

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Science China(Technological Sciences) 2019年第5期62卷 868-874页

作者： SHEN JieYi WU JianHua MA Fei College of water conservancy and Hydropower Engineering Hohai University

Nowadays, "Sponge Cities" are being built to provide a valid solution to the glaring drainage problems in the urban areas of China. The hydraulics of a dropshaft, especially discharge capacity, energy dissipation and cavitation damage control, evidently affect its safety and the city's underground tunnel system, due to the high dropshaft and large discharge. The hydraulic characteristics of stepped spillway dropshafts are experimentally investigated for the variable step rotation angles and end sill heights. Flow regimes inside the dropshafts are classified under the different approach flow discharges. The res.lts illustrate that there is high energy dissipation in the pres.nt dropshafts with the stepped spillway and the cavitation damage could be effectively avoided thanks to the effect of the air entrainment to the flow.

关键词： dropshaft end sill height hydraulic characteristics step rotation angle stepped spillway

A new design of ski-jump-step spillway

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Journal of Hydrodynamics 2016年第5期28卷 914-917页

作者：吴建华钱尚拓马飞 College of water conservancy and Hydropower Engineering Hohai University

A new kind of ski-jump-step spillway was reported. By means of the effects of the aeration basin, it supplies the sufficient aeration flow from the first step for stepped chutes, especially for large unit discharge. The physical model experiments demonstrated that, this spillway makes a far better hydraulic performance as regards energy dissipation and cavitation damage protection than the current and conventional stepped spillways, and the unit discharge can be enlarged from about 50 m3/s-60 m3/s.m to 118 m3/s.m in order to significantly reduce the width of the spillways.

关键词： cavitation energy dissipation pre-aeration ski-jump-step spillway

Measurement and assessment of water res.urces carrying capacity in Henan Province, China

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water Science and Engineering 2015年第2期8卷 102-113页

作者： Ming Dou Jun-xia Ma Gui-qiu Li Qi-ting Zuo College of water conservancy and Environment Zhengzhou University

As demands on limited water res.urces intensify, concerns are being raised about water res.urces carrying capacity（WRCC）, which is defined as the maximum sustainable socioeconomic scale that can be supported by available water res.urces and while maintaining defined environmental conditions. This paper proposes a distributed quantitative model for WRCC, based on the principles of optimization, and considering hydro-economic interaction, water supply, water quality, and socioeconomic development constraints. With the model, the WRCCs of 60 subregions in Henan Province were determined for different development periods. The res.lts showed that the water res.urces carrying level of Henan Province was suitably loaded in 2010, but that the province would be mildly overloaded in 2030 with res.ect to the socioeconomic development planning goals. The res.ricting factors for WRCC included the available water res.urces, the increasing rate of GDP, the urbanization ratio, the irrigation water utilization coefficient, the industrial water recycling rate, and the wastewater reuse rate, of which the available water res.urces was the most crucial factor. Because these factors varied temporally and spatially, the trends in predicted WRCC were inconsistent across different subregions and periods.

关键词： water res.urces carrying capacity Hydro-economic interaction Sustainable socioeconomic scale water res.urces carrying level Henan Province

EFFECTS OF HYDRAULIC AND GEOMETRIC PARAMETERS ON DOWNSTREAM CAVITY LENGTH OF DISCHARGE TUNNEL SERVICE GATE

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Journal of Hydrodynamics 2009年第6期21卷 774-778页

作者： MOHAGHEGH A College of water conservancy and Hydropower Engineering Hohai University

Aerators on discharge tunnel outlets may be regarded as an effective protection against.cavitation erosion. The air entrainment of aerators is governed by a number of independent parameters, including the bottom slope of releasing free-surface flow tunnel downstream of service gate, the end top slope of pres.ure tunnel, the height of step, and the Froude number at take-off. During eight phases of experiments, the effects of above-mentioned parameters were observed on the cavity length downstream of the fully open operating service gate of a discharge tunnel. The res.lts show that, the bottom slope of releasing free-surface flow tunnel has obvious effect on the cavity length as well as the Froude number at gate take-off. The effect of the step height variations on the cavity length could be considered for higher discharges and steeper tunnel top slope, particularly in higher discharges, res.lting in shorter cavity length downstream of service gate.

关键词： cavitation erosion cavity length discharge tunnel service gate