Abstract:Water conservancy policy in the new era and the general keynote of water conservancy reform and development such as accelerating the construction of water conservancy projects and strengthening the supervision of water conservancy industry put forward diverse requirements for talent cultivation in hydraulic engineering. To adapt to the requirements, professional construction and reform should be accelerated through learning, thinking and top-level design based on the list and analysis of insufficient promotion of education accreditation on the construction of water conservancy undergraduate majors. Eight aspects are suggested for advancing the major construction and reform, including versatile talent cultivation, cultivating mode reform, course system and curriculum reform, practical teaching system construction, innovative courses and teaching staff construction, university-industry cooperation and production-education integration, teaching methods improvement and quality assurance system perfection.

Abstract:In order to identify the health status of rivers and reveal the causes of river damage, index systems including 29 river health assessment index in 5 aspects were established based on the task of river chief system. The evaluation criteria and weights of the index systems were determined and a river health assessment model was proposed, which was applied to the Xining section inthe main stream of the Huangshui River. The results show that for the rule hierarchy, the water resources protection index is 60 points, water environment management indexis 65 points, water ecological restoration indexis 54 points, water pollution prevention indexis 35 points, water coastline management indexis 63 points. The Xining section in the main stream of the Huangshui River health index is 56 points, and the evaluation level is Ⅲ, belonging to the sub-health level and reaches the yellow warning. The river chief should organize to protect, repair, manage and control the river section to a certain extent.

Abstract:Based on the MODIS remote sensing products from 2000 to 2016 in the Yarlung Zangbo River Basin, the Normalized Difference Vegetation Index(NDVI)was adopted to demonstrate the changes of vegetation cover. Combined with the measured data from the meteorological stations in the basin, the trend analysis method, Hurst index method, and partial correlation coefficient method were used to investigate the response of vegetation cover to climate change. The results show that the NDVI in the upstream and downstream region in recent years was mainly improved, while that in the middle reaches was mainly deteriorated. The high value of NDVI was located in the low elevation area. The trend of vegetation cover against elevation was firstly stable, then downward, and finally stable again. The correlation coefficient between NDVI and temperature in the Yarlung Zangbo River basin was greater than that with precipitation, indicating that the impact of temperature on the growth of vegetation in the Yarlung Zangbo River Basin is much stronger than that of precipitation. The Hurst index across the whole basin showed a significantly spatial heterogeneity, with an average value of 0. 51, indicating that the NDVI of the Yarlung Zangbo River Basin showed a weak sustainability. The spatial sustainability of the NDVI in the Lhasa River Basin and the upper reaches of the whole basin was relatively strong, reaching the value of 0. 74.

Abstract:To study the reasonable roughness value of a long-distance channel, the roughness for a typical section of the Beijiang Water Transfer Project was inversely calculated using Manning formula based on the prototype observation water level and discharge data from 2011 to 2016. One-dimensional unsteady hydrodynamic model was established to verify the roughness value and its spatial difference between channel sections and temporal variation with performance period was analyzed. The results show that the measured roughness of the section is consistent with that of the straight channel section, the roughness of the straight section of the main channel is from 0. 015 to 0. 016. Correction for the effect of channel curves is from 1. 15 to 1. 50, which is related to the complexity of the curve. The channel roughness increases with the running time, and the annual increase of the equivalent roughness K_s was 18. 54 %.

Abstract:The variation of the monitoring effect quantity characterized the service behavior change of a concrete dam objectively reflects the working behavior variation of the dam. In order to ensure the safe operation of the dam, it is necessary to draw up the safety monitoring index of the corresponding monitoring effect quantity. Traditional method formulates the safety monitoring index under the assumption of certain failure probability, which is affected by the human factor. Aimingat the shortcomings of traditional approaches, integrated the idea of typical small probability method and analytic hierarchy process, the method of dividing the unequal range of evaluation grade attributes of concrete dam service behavior is proposed. The probability density function of monitoring effect quantity is constructed based on the principle of maximum information entropy, the method for formulating safety monitoring index of monitoring effect quantity corresponding to different grade attributes of dam behavior performance evaluation is put forward. The feasibility and effectiveness of the proposed method is verified by an engineering project.

Abstract:Due to the large terrain fluctuations, dense vegetation and some buildings for hydropower projects in high mountain areas, the problem of low accuracy of airborne LiDAR point cloud filtering always exists. A point cloud filtering method that includes the point cloud echo characteristic, a progressive triangulated irregular network densification(PTD)algorithm, an improved surface fitting algorithm and a refined ground point cloud filtering method was proposed. Based on the denoising of the airborne LiDAR point cloud data, the echo characteristics of the vegetation point cloud is first used to remove some vegetation points, and the PTD algorithm is applied to perform two iterative calculations to obtain a partial ground point set which is used as the seed point of the improved surface fitting algorithm to perform surface fitting of the grid area to obtain the ground points in the original point cloud data. Finally, the point cloud is refined to remove the low-level vegetation points included in the ground points to get the final ground points set. The measured data of the DJI-M600 equipped with the HS-600 airborne LiDAR measurement system was selected for experiments, and the proposed filtering method was compared with the PTD algorithm, surface fitting filtering algorithm, area growth filtering algorithm and morphological filtering algorithm. The results show that compared with the other four methods, the maximum reductions of the first type error, the second type error, and the total error are 6. 25%, 1. 82%, and 2. 93%, respectively. The proposed method is more suitable for the filtering process of airborne LiDAR point cloud data of hydropower projects in high mountainous areas.

Abstract:The water treatment agent composited by the sodium alginate encapsulated chitosan gel beads and the nano calcium peroxide gel beads coated with sodium alginate/polyethylene glycol 4000 were prepared to investigate its performance and mechanisms in the removal of phosphorus and organic matters in water. The physicochemical properties and morphology of the agent were characterized by X-ray diffraction, scanning electron microscope and elemental energy dispersive spectrometer. This composited water treatment agent can effectively remove single phosphorus or organic matters in water, and also has high removal efficiency for the complex phosphorus and methyl orange pollutants. The water treatment agent has higher adsorptive ability for phosphorus at high concentrationa real river. The slow release of oxygen can maintain the mass concentration of dissolved oxygen above 4. 5 mg/L, therefore providing better aerobic condition for microorganisms in muddy-water interface and elevating the ability of self-purification of water.

Abstract:Taking MPDI(modified permanent drawdown index)as an indicator of surface soil conditions under water utilization for human activities, a soil moisture neural network model with traditional natural factors was constructed to simultaneously consider the influence of natural elements and water use for human activities. The model was used to simulate the surface soil moisture in 2018 in Hebei Province. The results show that the simulation results of soil moisture content considering MPDI index are in good agreement with the measured values, with a correlation coefficient of 0. 7 in training period and 0. 5 in verification period. The soil moisture distribution of the neural network in a single day was analyzed and the correlation coefficient is 0. 67 for the example date, which indicates a good performance in revealing the spatial heterogeneity of soil moisture. The simulated results are consistent with the SMAP(Soil Moisture Active and Passive)products in Hebei Province, with higher values in summer and east plain, but with lower values in spring and northwest mountains.

Abstract:To study the cavitation characteristics of a high-speed submersible axial-flow pump in high flow conditions, three cavitation models including Zwart, Kunz and Schnerr-Sauer were selected and the external and the interior characteristics of the pump were simulated in high flow conditions based on ANSYS CFX. The results show that the prediction accuracy of Schnerr-Sauer model is most consistent with the experimental value in high flow conditions. Compared with the other two cavitation models, the volume fraction of bubbles on the suction surface of the blade is higher, and the area with serious cavitation mainly appears near the leading edge and at the top of the blade for Schnerr-Sauer model. The cavitation of the blades becomes more serious with the increase of flow speed at the same cavitation number. The load increases first and then decreases from the leading edge to the trailing edge of the blade. The bubbles generate at the leading edge of the suction of the blade at first and then expend to the trailing edge of the blade along the mainstream flow direction until occupying the whole blade suction with the decreasing of cavitation number. The cavities in the trailing edge of the triangle cloud cavitation at the back of the blade are extremely unstable. As the impeller rotates, the bubbles at the trailing edge gradually shed and move toward the adjacent blades, resulting in erosion damage and load change of adjacent blades, affecting the hydraulic performance of the axial-flow pump.

Abstract:To improve the simulation and judgment accuracy of leakage in pipeline systems, two distinct unsteady friction models, including the Brunone model of the transient acceleration type and the weighting function type(Zielke and Vardy models), were introduced to simulate the hydraulic transient leakage, and the results were compared with the experimental and simulation data in the published papers for further analyses. The calculated results show that Zielke model and Vardy model can simulate the pressure and flow signal changes more accurately compared with traditional friction models and the Brunone model due to simplification errors. The leakage leads to the distortion of pressure and flow because of new signal reflection caused by the leakage in the pipeline. Both the leakage discharge and position affect the degree of distortion, amplitude and attenuation of the transient pressure and the flow in the pipeline.

Abstract:To investigate the influence of local defects and damages on the tensile properties of geomembranes, different defects, e. g. , circular hole, horizontal seam, vertical seam and oblique seam, as well as damages of different lengths and depths were considered for HDPE geomembrane specimens of three thicknesses, respectively. Tensile tests were carried out by using an electronic universal tensile apparatus to obtain the major mechanical indexes such as tensile curves, tensile strength and elongation. Furthermore, the influences of different defects and damages on tensile properties were compared and analyzed. The results show that circular, horizontal and oblique defects or damages have significant reduction on the tensile properties of geomembranes, with the horizontal seam having the most significant effect on the whole, circular hole being the second, and oblique seam being the least. The greater the damage degree is, the more significant the attenuation of geomembrane mechanical properties is. The vertical seam along the stretching direction has little effect on the tensile characteristics of geomembranes, which can be basically ignored.

Abstract:To provide a simple determination method for structural parameters in the preliminary stage of sluice and to speed up the design progress, the influence law of sluice parameters on baseboard moment was summarized through abundant finite element analysis, which considering the main factors such as the elastic modulus of sand gravel foundation, the load on pier, the width of sluice gate, the thickness of the baseboard, the height of the pier, and the thickness of the gravel foundation. A prediction model of the central bending moment of baseboard based on multivariate nonlinear regression was proposed. The results show that the baseboard moment is nonlinear with the thickness of the baseboard, the width of sluice gate and the thickness of the gravel foundation, while it has a linear relationship with the height of the pier. The fitting effect of the proposed prediction model is good with high accuracy.

Abstract:Laboratory experiments and field tests of urban flooding are important approaches for model validation to improve the accuracy of simulation results. Advances in the research of urban flood characteristics by laboratory experiments were reviewed in three aspects, including the urban runoff generation process, the surface flood evolution, and the interaction of surface runoff with pipe network flow. Aiming at the shortcomings in the current study, it is necessary to improve the research on the mechanism of the surface runoff process through physical experiments and to intensify the research on the vertical interaction process between surface and pipe network flow. Quantitative experimental research on the associated processes closely intertwined with flow behavior during urban flooding should be strengthened.

Abstract:Anti erosion design is usually involved in the hydraulic design of hydraulic structures. It is generally stipulated that the anti-erosion design should be carried out in the area with cavitation number σ < 0. 3 or with the flow velocity greater than 15m/ s. The initial cavitation number is different in different parts of hydraulic structures. The value is analyzed not only through theoretical calculation, but also through pressure reduction model tests in which scale effect inevitably exists. The calculation formulas of primary cavitation number at home and abroad were summarized, and the advantages and disadvantages of different formulas and applicable conditions were put forward. The scale effects of primary cavitation were summarized, providing a new thinking method for the determination of incipient cavitation number in model experiment. The criteria of incipient cavitation in different parts of hydraulic structures were summarized, which provides specific and detailed guidance for corresponding design and research.