Abstract:Problems exist in the construction and management of ecological irrigation districts, such as low efficiency in industry and resources, irrigation water deterioration and decreased ecological diversity. Based on the theoretical guidance of the rural revitalization strategy and its 20 words general requirements, construction and management of ecological irrigation districts under the guidance of the rural revitalization strategy were discussed. Three red lines for the construction and management of irrigation districts were proposed, including the baseline of agricultural quality and production, the baseline of ecological environment and the upper limit of resources development and utilization. The ecological irrigation districts should develop in the direction of effective supply of food production and other products, perfection in ecological environmental landscape, protection and high-efficiency utilization of resources. This paper provides scientific references of sustainable and green development for ecological irrigation districts.

Abstract:In order to analyze the scale and water supplement route of a new water purification station in the northern area of Nanjing Qinhuai District, a one-dimensional water quality model of river network was established by coupling HD and AD modules in MIKE11. Ammonia nitrogen and suspended solids were selected as the research objects and the variation of water quality under different water supplement scales and water supplement routes was simulated. The result shows that the scale of 180 000 t/d for the new water purification station and connection of the outlet pipe to the sub branch of the Qinhuai River is appropriate.

Abstract:The AHP-entropy weight method-fuzzy comprehensive evaluation method was applied to discuss the development and utilization degree of the regional water resources in Xi’an City, and the evaluation model of water resources development and utilization was established. The results show that the development and utilization of water resources in Xi’an is in the middle stage, and the development and utilization potential index is 0. 552, which has a medium level of exploitation potential. Except for the urban area of Xi’an and Lintong District, the water resources development and utilization in other districts are in the initial or development stage. The AHP-entropy weight method-fuzzy comprehensive evaluation method is reliable and practical compared with other evaluation methods. Finally, Arcgis visualization analysis of water resources development and utilization in Xi’an City was carried out, which shows that the water resources development and utilization degree in the eastern part of Xi’an is higher than the western part.

Abstract:Most previous studies focused on the overall force on a cylinder, and the detailed mechanical characteristics for different parts of a cylinder were less studied. A 3-D numerical wave flume was used to investigate the internal solitary wave forces acting on cylinders by large-eddy simulation(LES). Through analyzing the hydrodynamic characteristics and the pressure distribution around cylinders, the detailed vertical distribution of the pressure drag force and viscous force was obtained. Based on multi-linear regression analysis, the comprehensive impact parameters were constructed to establish an empirical function of the force coefficients for the cylinders. The results show that the pressure drag on a square cylinder is 1. 5 times more than that on a circular one in the upper layer, while the pressure drag on a square cylinder is 3. 5 times more than that on its circular counterpart in the lower layer. The viscous force is 1 or 2 order of magnitudes smaller than the pressure drag, which means that the viscous force can be ignored. The comprehensive impact parameters show a positive correlation with the relative wave height, and show a negative correlation with the upper and lower water depth ratio.

Abstract:To investigate the hydraulic characteristics of a shaft tubular pump, the flow field and the pressure fluctuations at the impeller inlet, numerical simulation based on URANS method and a curvature corrected SST k-ω turbulence model was used to simulate the unsteady internal flow field in a shaft tubular pump with and without the groove control technique. The results show that the groove control technique has little effect on the pump performance, the flow field and the pressure fluctuations under the design conditions. When the flow rate decreases to the saddle area, the axial velocity in the impeller inlet decreases and the velocity circulation increases. The backflow region is extended with a large scale, which causes blockage of the inlet and low frequency pressure fluctuations. The groove control technique can effectively suppress the backflow vortices, increase the flow velocity uniformity and decrease the amplitudes of pressure fluctuations, resulting in an efficient improvement for the hydraulic characteristic of a shaft tubular pump in the saddle zone working condition.

Abstract:In order to solve the problem that some safety evaluation methods of sluice projects are not closely combined with the specifications, the health status of a sluice is divided into four grades according to the grading standards of the specifications. Based on subjective and objective combination weighting, a cloud model is used to judge the safety grade of each index, and as a result, the safety evaluation of a sluice project is realized from bottom to top. By analyzing and calculating the safety conditions of a practical sluice project, the feasibility and validity of the proposed method are verified. Starting from the industry standards, the evaluation model integrates the subjective and objective information into the safety evaluation of a sluice. The qualitative and quantitative grade evaluation of each index and the whole project are realized and the influence of uncertainties on the overall safety evaluation is effectively reduced, providing ideas for the operation, maintenance and management of sluices.

Abstract:Aiming at the problem that a single sensor signal can only reflect the local characteristics of a structure and is susceptible to interference, a data level fusion method based on correlation variance contribution rate is proposed. Data fusion can be realized through allocating the fusion coefficients by calculating the variance contribution rate of the signals from multi-sensors. The data fusion results of the observed prototype signal of Jinping I high arch dam and the measured signal of a self-made RCC dam hydroelastic model show that the proposed method has good noise resistance, and it can mine high-frequency weak information and dense frequencies in vibration signals. Compared with the method based on correlation function, this method make the fused signal can fully reflect the overall vibration characteristics of the dam body, and it is suitable for modal parameter identification of the vibration signals from high arch dams and roller compacted concrete dams.

Abstract:A system analysis model for dike engineering based on Hall three-dimensional structure was proposed and a technical framework for risk assessment and management of dike engineering during the whole process of design-construction-operation was established. The scope definition in risk analysis, identification of risk factors and working key points in risk factors analysis were clarified. Three key reasons for dike-break in the risk analysis were addressed. The methods for calculating the risk rate and assessing the dike-break risk applicable to different stages were discussed. The risk evaluation and benefit analysis of dike engineering corresponding to different stages were analyzed. The technical processes and implementation points for solution selection and countermeasures for risk control, dynamic monitoring and information feedback were also discussed. The obtained workflows and technical solutions for risk assessment and management of the dike engineering during the whole process of design-construction-operation are expected to be gradually applied and developed in practice.

Abstract:In order to study the joint influence on flood propagation caused by the wharf groups located at different reaches of the Yongjiang River, the influence of the wharf groups on channel flow characteristics under typical tidal and flood conditions was studied based on the numerical model of Delft3D. The results show that the backwater level is higher if the location of the wharf group is farther from the estuary and the distribution of the wharves is denser. In the backwater influencing region induced by different single wharf groups, the increase of flood level caused by all of the wharf groups is higher than that caused by each wharf group. In the area where both backwater and water level drop caused by different wharf groups exist, part of the water level variation can be balanced out. However, due to the degree of water level drop is lower than the backwater, water level during flood discharge still increases. The velocity decreasing zone surrounding the wharf project and the velocity increasing zone in the main channel both show a zonal distribution. The velocity variation caused by all of wharf groups is more than that induced by every single wharf group and the degree of velocity reduction is greater than velocity increase.

Abstract:To improve the precision and to further complement and perfect the calculation theories for jet trajectory distance, a calculation method for the upper and lower jet trajectory distances in the perspective of the takeoff velocity was proposed. Based on the concentric circle assumption of the streamline on the flip bucket with the consideration of the centrifugal force and the hydrostatic pressure, the potential flow velocity distribution function was derived. Theoretical calculation formulas for the velocity of the upper and lower trajectory were obtained from the takeoff velocity distribution and then the jet trajectory distance calculation was realized. The calculation method was verified by both model tests and prototype observation datum, showing a reasonable accuracy for the upper and lower trajectory distance when the relative takeoff water depth is between 0. 15 and 0. 25.

Abstract:Due to serious sediment deposition in the upper reaches of Wudingmen sluice in the outer Qinhuai River in Nanjing, a physical model was established and two schemes were designed to study the silt reduction effect of a diversion wall with a 15°deflection angle in the upstream of the sluice. In scheme 1, a scope of 60 m upstream of the sluice was excavated to the design section. After two years and eight months of flow and sediment process, the sediment volume in the regulated section was reduced by 30. 4% after the diversion wall configuration. In scheme 2, a scope of 240 m upstream of the sluice was excavated to the design section also with a diversion wall. The sediment volume of the regulated section was reduced by 50. 8% and 44. 0% after one and two typical hydrological years respectively. The range of sediment reduction decreased, the riverbed tended to form a new balance between erosion and deposition, and the topography of the section tended to show a uniform distribution. The results show that the diversion wall with a 15°deflection angle can significantly reduce the siltation in the upstream of the Wudingmen sluice and can improve the flow capacity of the channel.

Abstract:Taking various internal and external boundary conditions of pumps, valves, air valves, surge tanks, heterogeneous series of pipes and the downstream reservoir into consideration for a long-distance pressurized water transfer system, water hammer induced by pump failure in engineering construction was discussed based on the characteristic difference method. Sensitivity analysis of the time interval of pump restarting after pump failure and the roughness of the pipeline was carried out by numerical method. The results show that the reasonable time interval between pump failure and pump restarting can improve the hydrodynamic characteristics of the pressurized water transfer system as well as its components in the hydraulic transition process, which can reduce the size of the surge tank and the engineering cost. The roughness affects head loss and water hammer attenuation but has little influence on the hydrodynamic characteristics of the whole system in the hydraulic transition process.

Abstract:A three-dimensional finite element numerical model was constructed to simulate a defected geomembrane on a slope based on the two-electrode method. The potential distribution near the surface defect was obtained and the potential distribution in different detection line directions was analyzed. The impact of the detection line direction and position on the leak detection sensitivity was further investigated. The results indicate that the positive electrode should be separated from the defect to prevent its shielding effect on the defect. The distance between the detection line and the defect center should not exceed 0. 2 m if the detection line connected to the main electrode is in the direction perpendicular to the defect. The distance between the detection line and the defect center should not exceed 0. 1m if the detection line connected to the main electrode is in the direction parallel to the defect.

Abstract:Combining the latest domestic and international research results with related engineering cases, the updated research progress on the vibration inversion and safety control index of discharge structures were reviewed from the aspects of dynamic inversion of material parameters, vibration source identification and vibration safety control index of flood discharge structures. The key issues of vibration safety for current flood discharge structures were summarized. It is pointed out that the future research on vibration inversion and safety control index of flood discharge structures should be focused on the innovation of the mathematical model of material parameter inversion and corresponding solving algorithms, the time-domain identification of vibration source load and equivalent load processing, the vibration fatigue safety control standards and comprehensive assessment methods of human comfort.

Abstract:Vegetation is an important feature of a fully functioning river ecosystem. The KH vortex, a special coherent structure generated in submerged vegetated flows, has direct influence on the flow-sediment-contaminant transport. Advances in related issues on KH vortex in vegetated turbulent flows were reviewed from the aspects of the discovery, the formation conditions, the parameter characteristics of the geometrical form and the period of KH vortices. The main effects of vegetation density and submergence on KH vortices were summarized. It is suggested that the key issues to be further explored should be focused on the critical conditions for the KH vortex formation such as the critical density or the submergence, the development progress along the streamwise direction and the specific influence of the factors(such as density, rigidity and geometry of vegetation, submergence and flow intensity)by coupling the turbulence instability theory, spectrum analysis, flow visualization and image technique.