In order to verify and optimize the “dragon-drop-tail” layout plan of the No. 1 flood discharge tunnel in the expansion project of the Chentianhe Reservoir, a numerical calculation model for the discharge was established. The numerical feedback of cavity backwater behind the airfoil flip bucket of indoor experiment was made use of to calculate the rationality of the numerical model. The optimal objective function of the shape of the airfoil flip bucket was identified based on the principle of safety and economy. The feedback model was then used to optimize the layout of aeration devices. The research shows that results of the simulation which adopts the FAVOR and Tru-VOF methods of structured rectangular grids, the RNG κ-ε turbulence model and the numerical model of fine grid are in line with indoor experiment results in terms of cavity shape and length. The optimal values of the bucket angle α and slope rate of the bottom slope behind the airfoil flip bucket θ of the No.1 flood discharge tunnel are 10% and 20%, respectively.

In order to improve the water environment carrying capacity of Nanchang during the dry period, this paper constructed a water environment model at the lower end of the Ganjiang River and proposed an optimal scheduling scheme. The results show that the optimal scheduling water levels for the Ganjiang main river and its four downstream branches-the main, the north, the middle, and the south-were between the minimum ecological water level and the alert control water level, and that the scheduling time was within 1.11 days when the flow rate was less than 1 020 m³/s. Conversely, when the flow rate was greater than 1 020 m³/s, the alert control water level was the flood control limit water level. The optimal scheduling water levels of the main river and the four branches were between the minimum ecological water level and the flood control limit water level, and the scheduling time was within 4-7 d. It was suggested that each branch barrage hub should be operated close to the alert control water level to ensure that the water quality of the river control section meet the standard, and to maintained the maximum amount of water resources available in Nanchang.

By investigating the historical meteorological data, disaster situation data and disaster bearing body information during 1951-2020, this paper establishes a risk survey database to accurately evaluate the hazard of rainstorm disaster in Changsha County of Hunan Province. Comprehensively considering the impact of multiple meteorological disaster causing factors of rainstorm disaster and inducing environment such as geology and drainage network of watershed, this paper carries out the analysis of basic characteristics of rainstorm and risk assessment of disaster, and forms a risk assessment model. Geological disasters in Changsha County mainly occur in the northeast of Changsha County. The urban waterlogging disaster mainly affects the county seat and the surrounding areas with high urbanization. Mountain torrents mainly affect the central and northern areas of Changsha County. The risk of rainstorm disaster in Changsha County tends to weaken from the southeast and northeast to the middle. Generally speaking, the risk of rainstorm in the whole county is not high, only Kaihui Town, Gaoqiao Town and Huanghua town are high-risk, and rainstorm events are easy to cause secondary disasters in these three towns. There are two relatively high value centers in the county, which are located in Huanghua town and Jiangbei town in the southeast and Kaihui town and Gaoqiao Town in the north. The comprehensive risk level of rainstorm in Ansha Town, Guoyuan Town, Chunhua Town and urban area in the middle is low.

In order to better understand the impact of vegetation restoration on hydrological processes, the SWATMODFLOW model and dynamic HRU was coupled, and LU-SWAT-MODFLOW model was developed to accurately simulate the dynamic change of vegetation and groundwater in the lower reaches of the Bayin River Basin. The results revealed that the LAI, ET and groundwater level simulated by LU-SWAT-MODFLOW model are better; After vegetation restoration in the study area, the monthly evapotranspiration of different sub-basins increased by 0-1.5 mm, and the annual evapotranspiration increased by 0-6 mm; The average monthly groundwater recharge increased about 1.27 mm, and the average annual groundwater recharge increased 14.02 mm. The exchange of the surface water and groundwater in the study area have obvious changes in the areas where the vegetation restoration type is low-coverage grassland and bare land converted to forestland.

In view of the differences between national, continental and global scale precipitation data sets, there are many studies, but the reliability of data sets on river basin scale is rarely considered. To this end, the maximum/minimum difference percentage method and TFPM-MK trend analysis method were used to study and evaluate the differences between 12 widely used precipitation data sets in precipitation estimation and change trends in 6 292 basins around the world. The results show that there are large differences between precipitation data sets. There are 2 469 basins with an annual average precipitation difference of more than 500 mm/a, covering an area of 4 419.6×10⁴km², mainly distributed in Greenland, Africa, Oceania and West Asia. The existing data products cannot reach an agreement on the precipitation trend of all basins, and it is difficult to provide a reasonable scientific basis for the formulation and implementation of effective policies to ensure water conservancy and power generation, domestic water supply, flood control and early warning in the basin.

The "reinforced concrete shield and riverbed" junction or pre-excavated pits at the end of the apron of a gate dam with supercritical flow connection mode are often damaged by foundation erosion, which not only leaves the apron in a suspended state, but may also cause the flow pattern at the end of the apron to deviate from the designed supercritical flow pattern, or even form a hydraulic jump like large-scale rolling and scouring riverbed, but there are few relevant research results. For the scenario that suspended foundation at the end of apron caused by local generalized scouring, the detailed observation and computational analysis of the flow patterns near the scour pits of different sizes at the end of the apron were carried out using physical model experiments and three-dimensional turbulence numerical modelling methods. Compared to the supercritical flow pattern at the end of the apron when the foundation is not scoured, the results show that the scour pits change the flow pattern significantly, and can be divided into three categories. The first category is the hydraulic jump upstream of the apron, the second category is the mixed flow in the scour pit and the third category is the quasi-periodic flow pattern consisting of the first two categories. The results of the flow evolution study can provide technical support for the analysis of large-scale damage to the retaining structure downstream of the dam apron, which has certain engineering application value.

In order to realize the effective utilization of winter idle water resources in kariz of Turpan Basin and recharge the regional groundwater, it is urgent to carry out groundwater recharge project in this area and determine the reasonable construction location and effective recharge mode. Firstly, the suitability evaluation system of groundwater recharge was constructed based on the six indexes of kariz flow, recharge source distance, aquifer permeability coefficient, groundwater depth, electromechanical well density and terrain slope. The suitability zoning of groundwater recharge was carried out by using ArcGIS spatial analysis function. Field tests were carried out in the typical recharge suitable areas to study groundwater recharge methods. The results show that there are abundant recharge water sources and storage space in the middle of Gaochang District, the north basin irrigation area of Shanshan County and the northeast part of Toksun County. The overall permeability coefficient is greater than 15m/d, which is suitable for the recharge of kariz winter leisure water. The effective recharge of groundwater can be realized by using the well irrigation method of the electromechanical well recharge, which is suitable for the recharge of the winter idle water in the study area.

Conventional and wetting triaxial experiments were carried out on coarse grained materials for dam construction with a large static and dynamic triaxial tester. The dynamic characteristics of coarse grained materials after wetting deformation were studied, and the results were compared with those of conventional triaxial dynamic experiments. The experimental results show that the dynamic characteristics of coarse grained materials are greatly affected by wetting deformation, and the dynamic performance parameters of coarse grained materials are attenuated to a certain extent. The Hardin-drnevich model parameters of the two experiments were compared and analyzed. It was found that wetting deformation had a significant effect on k₂ and λ_max, and the numerical values were attenuated, but the effects on n and k₁ were not significant.

In order to ensure that the conductor length of multiple parallel coils of power transformer is consistent and the current density is balanced, the structure transposition is usually carried out in the winding process. The actual operation shows that the insulation at the conductor transposition is easy to damage and leads to inter-turn short circuit fault. Aiming at the problems that the fault point is difficult to set and the electrical quantity cannot be directly detected in the actual test, this paper uses the 'field-circuit' coupling principle to take the distribution transformer with the model of S13-M-200/10, the low voltage winding is wound by two flat copper wires and the transposition point is in the middle of the winding as an example. Based on the finite element simulation software, the simulation analysis model with the same size as the physical structure is established. Through the comparison of the actual test value and the simulation analysis value of the performance parameters, on the basis of verifying the correctness of the model, the electrical characteristics and electrodynamics of the low voltage winding of the power transformer are studied when the single inter-turn short circuit occurs at the conductor transposition. The results show that when a single inter-turn short circuit occurs in the low voltage winding of the transformer, the loop current of dozens of times the rated current flows inside the short circuit ring, the fault phase current decreases slightly, and the active power loss increases sharply. Conductor transposition causes uneven distribution of axial force and radial force of the coil, and the winding is prone to instability and deformation. It is necessary to take mechanical and insulation strengthening measures at the conductor transposition.

The plane gate controls water storage and discharge by opening and closing, and is easily damaged by the pulsating pressure of the water flow during operation. In order to study the interaction process between the opening and closing motion of the gate and the flow through the gate, this paper firstly conducted a three-dimensional numerical simulation of the flow through the gate during the opening and closing process of the gate under different bottom edge forms. And then the Hilbert-Huang transform was used to analyze the flow through the gate, and the time-frequency-amplitude information of the signal. The information analysis and comparison found that the bottom edge of the combined gate with a forward tilt of 45° and a backward tilt of 30° is gently affected by the pulsating pressure at the bottom of the gate, and the change difference of the energy amplitude at the measuring point was the smallest, and the water flow state was relatively stable. This study can provide a reference for the analysis of the pulsating pressure of the water flow through the plane gate.