Based on Hopf bifurcation theory, the stability of pumped storage power station considering asymmetric water passing system is studied. Firstly, the mathematical model of the speed regulation system of the pumping and storage unit of the one-pipe two-machine asymmetric water passing system with the upstream surge chamber is established. On this basis, the Hopf bifurcation analysis is carried out to obtain the theoretical stability region of the speed regulation system, and the dynamic response characteristics of the unit under different control parameters are analyzed to verify its theoretical stability region. Furthermore, the multi-scale oscillation characteristics and its generation mechanism of the dynamic response of a pipe double pump storage unit are revealed. Finally, the influence laws of flow inertia time constant, turbine inertia time constant and surge chamber time constant on system stability are explored. The results show that the Hopf bifurcation of the speed control system of the pumping and storage unit of the one-pipe two-machine asymmetric overflow system with the upstream surge chamber is supercritical, and its stability region is determined by two bifurcation lines; The hydraulic interference between the surge chamber and the units makes the response characteristics of the units show obvious multi-scale oscillation characteristics; Larger flow inertia time constant and smaller turbine inertia time constant are beneficial to system stability, and the influence of surge chamber time constant on system stability presents saturation characteristics. The research results have important guiding significance for the intelligent control of pumping and storage units and the design optimization of water passing system in power stations.

In order to study the effect of arrangement of non-submerged rigid vegetation on surface flow hydraulic characteristics, this paper established a hydraulic model based on the actual situation. The average vegetation was evenly arranged as the control group, the vegetation was arranged in a strip pattern and the distance between the strips increased in multiples of 1.333, 1.667, 2.000, 2.333, 2.667, while the distance within the strips decreased by 0.833, 0.667, 0.500, 0.333, 0.167 as the experimental group. The numerical simulation based on Fluent verified the effects of changes in the arrangement of vegetation with the 5% coverage (210 plants) on the water flow and hydraulic characteristics. The results show that the vegetation coverage was the same and the vegetation arrangement tended to be uniform. Under the influence of water depth, the flow rate decreased, and the Reynolds stress in the lower half of the water depth increased. The surface flow rate on the non-submerged vegetation decreased, and the turbulent flow increased. The water energy is consumed to prevent water and reduce the erosion of water surface. This study provides reference for flood control and disaster reduction.

For the value of the surrounding rock parameters of the underground construction, a hybrid network approach combining backtracking search optimization algorithm (BSA) and BP neural network (BSA-BP) was proposed for the inversion study of the tunnel surrounding rock parameters. By establishing a tunnel finite element excavation model, the inversion parameters were used to calculate the displacement of the monitoring section and compare with the measured values in the field. Finally, the stability of the surrounding rock was analyzed and predicted. Compared with the GA-BP neural network, the results show that the BP neural network optimized by BSA algorithm has faster inversion speed and computational efficiency. The relative errors between the calculated displacement values and the field measured values obtained by using BSA-BP neural network inversion parameters are within 5%, indicating that the model has high inversion accuracy and is reasonable and feasible. The research results provide a new method for the inversion of underground engineering parameters.

Considering the characteristics of inversion problems of concrete face dam, including high dimensionality, complex calculation and excessive calculation time, the orthogonal experimental design was used to construct the learning sample composed of the combination of permeability coefficient and the water head of pressure measuring point. The nonlinear mapping relationship between the water head at monitoring points and permeability coefficient was established by general regression neural network (GRNN), and the particle swarm optimization (PSO) algorithm was used to search for the smoothing factor σ suitable for the specific project to improve the generalization and convergence speed of the model. The PSO-GRNN model for the inversion of the permeability coefficient of concrete face dam was established, and was applied on an engineering example. The results show that the value of permeability coefficient obtained by inversion based on the model is reasonable, and the maximum relative error between the calculated value of water head at monitoring points obtained by seepage analysis and the measured value is 3.64%, and the accuracy meets the needs of engineering.

The outlet area of river diversion tunnel in mountainous areas is characterized by large discharge per unit width, high flow velocity, deep riverbed overburden and low anti-scour flow velocity. The river bed at the outlet of the tunnel is severely scoured, and it is difficult to arrange large energy dissipation measures, so it is proposed to arrange small flip bucket at the outlet of the tunnel. On the basis of the physical model test to observe the flow pattern and river bed scouring in the outlet area of the tunnel, the numerical simulation method is used to calculate the flow field in the outlet area of the diversion tunnel, and the internal mechanism of the improvement of river bed scouring is studied. The results show that after adding a small flip bucket at the outlet of the diversion tunnel can increase the lateral diffusion of the high-speed flow out of the tunnel, reduce the unit width discharge, increase the local energy dissipation rate, and thus reduce the velocity of the river bank. The proportion of water body coming out of the tunnel with high flow velocity is obviously reduced, which makes the high-speed water flow unable to directly rush the landslide mass on the right bank, and reduces the flow velocity within the landslide mass. The width of water flow out of the tunnel increases, and the direction of water flow out of the tunnel becomes inclined upward, which weakens the impact on the landslide on the right bank, and significantly weakens the scouring of the outlet area of the diversion tunnel and the downstream river channel. This study can provide reference for engineering practice.

In order to accurately judge the start and end time of snowmelt period, the upstream of the Danba basin, the main source of snowmelt runoff in Daduhe River, was taken as an example. Based on hydrometeorological data from 2009 to 2020, set pair analysis method, systematic clustering method and K-means clustering method were used to calculate the snowmelt period in the dry season (November to the next May), and the rationality of the staging results was evaluated. The division scheme of final snowmelt period in the basin was determined. The results show that the main snowmelt period is from January 11 to May 10, the preceding period is from November 1 to January 10, and the following period is from May 11 to May 31, which is the beginning period of rainfall runoff (there is still some snowmelt runoff). The research results can provide reference for the classification of snowmelt periods in high latitude areas.

Aiming at the problems such as unstable design quality, long design cycle and large repetitive workload in the current gate design, based on the whole process three-dimensional parametric design concept, and according to the design specifications and manuals, a three-dimensional parametric design method for the whole process of gate is proposed, that is, the three-dimensional parametric geometric modeling, spatial structural analysis and engineering drawing of plane gate structure are realized on the same platform by writing corresponding programs. This method can make the gate structure transition from plane design to space design, make the design process more intuitive, improve the quality and efficiency of the design, reduce the repetitive workload caused by design changes in design process.

Integrating reclaimed water into water supply system is a strategic measure to alleviate the problem of water resource shortage. Aiming at the uncertainty and stability existing in the optimal allocation of multiple water sources including reclaimed water, Monte Carlo simulation and interval two-stage robust stochastic optimization were coupled to build the optimal allocation model of multiple water sources under the condition of multiple uncertainties. The uncertainty represented by the form of interval and probability distribution in the process of water supply and water demand was effectively handled. The variable random value of water resources allocation and the recourse cost were balanced, and the system’s risk was controlled. The water resources allocation schemes were obtained under different scenarios. The improved model was applied to water supply area in Linfen Basin-Jincheng Qindan river watershed of Shanxi large water network. Based on the comprehensive analysis of regional water efficiency and water loss under different scenarios, the joint allocation scheme of multiple water sources under different utilization rates of reclaimed water was obtained, which provides a reference for decision makers to consider the optimal allocation scheme of reclaimed water under uncertain conditions.

When upstream and downstream water regime changed in long-distance pressurized water delivery pipeline of cascade pump stations, it is easy to cause the change of water pressure in pipeline and hydraulic parameters such as flow velocity, and results in water hammer. In order to meet the water delivery requirements of the pipeline and ensure its safe operation under various working conditions, one-dimensional characteristics method and 3D VOF coupled methods were used to simulate. The mathematical model for transient process analysis of long-distance water delivery system of cascade pump stations was established to analyze the change and law of pipeline internal pressure and water level in outlet pool during long-distance water delivery system in Chuhe Level Ⅳ station of Simashan River Diversion Project under working conditions, such as suspending period and power losing period. It also shows that the safety of the entire pipeline system can be better guaranteed though the reasonable open-close laws of the terminal gate and side gate.

Aiming at the evaluation of water resources security in China, combined with the characteristics that support vector machine (SVM) has good classification effect on small samples and nonlinear problems, the sparrow search algorithm (SSA) was used to optimize the penalty factor (C) and kernel function parameters (g) of the SVM. The support vector machine model optimized by the sparrow search algorithm (SSA-SVM) was used for regional water resources security assessment. A case study was carried out in a certain area of Luoyang City. The results show that the evaluation grade obtained by SSA-SVM method and T-S fuzzy neural network method are basically consistent, the SSA-SVM model has the characteristics of fast searching speed, and not easy to fall into local optimum, which can be used for regional water resources security evaluation.