The problem of poor flow conditions in the bell-shaped inlet suction chamber of a large vertical submersible axial flow pump station was addressed, which resulted in poor water inflow conditions and low pump efficiency. Based on the Reynolds time-averaged N-S equations and the Realizable k-ε turbulence model, the structural optimization of the bell-shaped inlet guide cone of the pumping station was carried out using numerical simulation. The hydraulic loss of the inlet flow channel, the uniformity of the outlet velocity distribution and the average angle of water flow into the pump were selected as evaluation indicators to optimize the size of the elliptical guide cone within a reasonable range, and numerical simulation as well as performance comparison analysis were performed. The results show that the optimal semi-major and semi-minor axis dimensions of the guide cone are a=1.0D and b=0.4D, respectively. After optimization, the recorded hydraulic loss of the inlet passage is 0.189 m, indicating a reduction of 0.028 m compared to the original value. The outlet flow velocity uniformity is 94.28%, indicating an improvement of 10.96%. The average water inflow angle into the pump reaches 87.80°, reflecting an increase of 1.02°. The efficiency and head of the pump unit improves significantly after optimization. At the design flow rate of 7.0 m³/s, the efficiency increases from 64.39% to 67.74%, the head increases from 9.62 m to 9.98 m, and the maximum pump efficiency improvement reaches 5.81%. A model test is conducted for the optimized design. Under the design flow rate, the test efficiency is 67.03%, with a corresponding head of 9.82 m, indicating high performance. The simulated performance curves show good agreement with the experimental results, and the maximum efficiency deviation is less than 3%, demonstrating the reliability of the simulation results. The research findings provide valuable references for the design and optimization of bell-shaped inlet flow channels in similar pump stations.

In order to achieve the goal of ″Carbon Peaking and Carbon Neutrality″, and actively promoting the development of clean energy, pumped storage technology has been widely used as an important means to maintain the security of the power grid. However, the operation of large head pump turbines may have problems such as vibration and noise caused by the ″S″ characteristic zone, so it is important to conduct an in-depth study of the characteristics of the ″S″ zone based on numerical calculations. The typical operating conditions of large head pump turbines based on numerical calculations were investigated, and the pressure distribution and vortex flow in the ″S″ zone were analyzed by steady-state numerical calculation method. It is found that when deviating from the design conditions, a water retaining ring will be formed in the bladeless area, which will hinder the water flow into the runner and cause the vortex to block the flow channel. Based on the revealed instability mechanism, a solution is proposed to improve the hydraulic characteristics by optimizing the impeller structure, which successfully and effectively controls the vortex flow in the flow channel, significantly reduces the flow separation phenomenon, and thus improves the operational stability of the unit. The research results can provide theoretical guidance for the optimization design of pump-turbine with large head variation.

Based on a high-speed photography technology test bench, the dynamics of a bubble collapse at the symmetrical positions of double cylinders within a narrow gap were experimentally investigated. The growth and collapse of cavitation at different initial positions were qualitatively analyzed, and typical experimental phenomena at three dimensionless distances were summarized. Furthermore, the characteristics of cavitation morphology evolution, centroid movement, bubble interface motion, etc., under different dimensionless distances were quantitatively explored. The main conclusions of the study show that based on the dimensionless distance of the cavitation(l^*), the dynamic behavior of the cavitation at the symmetrical position of double cylinders can be summarized into three typical cases: for case 1(l^* is small), the left and right sides of the bubble interfaces are significantly concave, and no jet occurs. For case 2(l^* is medium), the left and right bubble interfaces are weakly concave, but a jet occurs. For case 3(l^* is large), the right side of the bubble interface is concave, but a jet occurs. The evolution of the bubble wall morphology on the side away from the double cylinders is more violent than that close to the double cylinders, and the intensity increases with the increase of the dimensionless distance. At the symmetrical position of double cylinders, the roundness and centroid movement distance of the cavitation bubble during its collapse are directly proportional to the collapse radius and dimensionless distance.

To study the gas-liquid-solid flow characteristics and working performance of hydrocyclone valves with different structural types, numerical simulation calculations of the gas-liquid-solid flow of hydrocyclone valves with three different structural designs were conducted based on the VOF and DPM models. The research results indicate that structural design can control the volume distribution of the gas phase, thereby affecting the flow characteristics and working performance of the hydrocyclone valve. By changing the equivalent radius, cavity width, and outlet diameter, the velocity streamline distribution, particle velocity, and particle size distribution in the water collection well, hydrocyclone valve, and downstream pipeline can be affected, resulting in hydrocyclone valves with different working performance. The gas-phase distribution area occupies the spatial distribution of particles and promotes the deposition of particles in the collection well. The flow resistance and interception characteristics of the hydrocyclone valves are related to the swirl and vortex formed by the gas phase distribution. Under the current working conditions and water collection well design, the R300 mm×L150 mm×d200 mm structure should be preferred. Its smaller resistance coefficient ensures a certain flow capacity, while the larger interception ratio does not cause secondary pollution due to water collection well overflow. For the off-peak scheduling conditions where only overflow of the water collection well is considered, the R300 mm×L200 mm×d280 mm structure and the R300 mm×L150 mm×d200 mm structure can be selected according to actual conditions. The research results provide a certain reference basis for expanding the operating conditions of hydrocyclone valves, as well as improving their selection capabilities.

In order to study the dynamic characteristics of cavitation during the periodic evolution of cloud cavitation, a one-way coupled Euler-Lagrangian hydrodynamic cavitation simulation method was proposed based on the homogeneous flow model and the discrete phase model. Numerical calculations were carried out for the cloud cavitation flow over a two-dimensional Clark-Y hydrofoil with a cavitation number of σ=0.8, and the instantaneous lift coefficient and cloud cavitation evolution on the suction surface of the hydrofoil were obtained. By solving the spherical cavitation dynamics equation, the evolution pattern of cavitation dynamics in the cloud cavitation area of the hydrofoil was also acquired. The research results indicate that this numerical method effectively simulates the periodic behavior of cavitation in hydrofoils during the cloud cavitation. The intensity of the pressure on tracer particles along their paths is influenced by the position of cavitation shedding and collapse. The internal pressure of the cavitation is related to its subjected flow field pressure. The more drastic the flow field pressure change, the higher the amplitude of the internal pressure of the cavitation, and the larger the pressure wave released by its collapse. When the cavitation radius shrinks to 15.7 μm, the maximum amplitude of its collapse pressure can reach 69.800 MPa. As the initial radius of the cavitation increases, the amplitude of cavitation internal pressure decreases, and the cavitation morphology remains basically stable. The research method in this paper can provide a theoretical reference for the study of spherical cavitation dynamics in other types of large hydraulic machinery.

To investigate the influence of the dynamic deformation of the flexible cantilever hydrofoil on its hydrodynamic performance, a flexible cantilever hydrofoil was taken as the research object. Firstly, the key parameters characterizing its deformation characteristics were extracted, and the mathematical model of flexible cantilever hydrofoil deformation was established. Then, using the dynamic grid technology, the effects of hydrofoil bending torsional coupling deformation and single deformation(bending vibration and torsional vibration)on hydrofoil hydrodynamic performance under three typical hydrofoil attack angles of 2°, 4° and 6° were analyzed. The results show that torsional deformation has a more significant impact on the hydrodynamic performance of hydrofoils compared to bending deformation. Along the spanwise direction from the constrained end to the free end, the amplitude of the deformation frequency in spectrum gradually increases. At larger angles of attack, the lift and drag coefficients near the constrained end of the hydrofoil are influenced by the coupling of deformation frequency and vortex shedding frequency. On the pressure side, the pressure fluctuation amplitude distribution corresponding to bending and torsional frequencies exhibits substantial differences, and the pressure fluctuation amplitude distribution characteristics of combined deformation can be regarded as a superposition of those corresponding to bending and torsional frequencies.

In order to effectively improve the safe and stable operation level of the power grid as well as the utilization rate of new energy resources, a refined model of a variable-speed pumped storage unit, including a pressurized water intake system, pump-turbine, alternating current(AC)excitation gene-rator, and governor, was established. In-depth calculation and analysis were conducted on typical hydraulic transient processes of pumped storage power stations. The research results show that the numerical simulation model of the AC excitation variable-speed unit can effectively simulate each working condition, and the simulation dynamic process is consistent with the actual operation process of the unit, with good results. When the variable-speed pumped storage unit increases or decreases the load under the governor power model of the power generation condition, the unit speed is controlled by AC excitation, and its speed can be quickly and accurately adjusted, and the active power on the stator side can also be quickly stabilized at the specified value. When the unit increases or decreases load under the governor opening model of the power generation condition, the unit output is controlled by AC excitation. The active power on the stator side can be quickly stabilized at the specified value, while the rotational speed of the unit is slowly stabilized at the specified value.

The river network in Yaozhuang Polder Area of Jiashan County has a low-lying terrain and a complex structure, resulting in problems such as slow water exchange rate and insufficient hydrodyna-mics. A two-dimensional river network hydrodynamic model based on MIKE21 was constructed, and by taking the minimum energy consumption cost of gate-pump operation as the main objective function, as well as taking the flow velocity, gate-pump flow rate, and water passage time as constraints, a joint gate-pump regulation and optimal scheduling model was established. The Grey Wolf optimization algorithm was used to solve the model, resulting in a more economical and efficient regulation scheme. The hydrodynamic regulation effect under the different regulation schemes was simulated and analyzed. The results show that, under the optimal scheduling scheme, the total power consumption of each pumping station and sluice gate station reduces by 67.95%, the hydrodynamic improvement effect enhances significantly, the average flow velocity and the maximum flow velocity of the river channel increase significantly, the length of the dead water section shortens, and the overall maximum flow velocity of the river network reaches 0.325 m/s. The most prominent point is the South Yiwan river section, with the increase of flow size around 50%-80%. The results of the study provide technical support for the joint regulation and control of gates and pumps in China′s plain river network.

In order to explore the impact mechanisms of mulching and biochar on soil hydrothermal and inorganic distribution, as well as yield in controlled irrigation paddy fields, four treatments were set up: no mulching and no biochar application(CK), film mulching(CF), application of 2.5 t/hm² biochar(CB), and combined film mulching with application of 2.5 t/hm² biochar(CBF). The spatiotemporal variation trends of soil hydrothermal, inorganic nitrogen, crop yield, and their components in different soil layers of paddy fields under mulching and biochar conditions were analyzed. The correlation characteristics of soil hydrothermal, inorganic nitrogen, and yield under the combined application of mulching and biochar co-cultivation conditions were quantified. The results demonstrate that, compared with the control(CK), different mulching and biochar treatments significantly enhance soil moisture content, ammonium nitrogen, and nitrate nitrogen levels. The CBF treatment shows the most pronounced improvement, with increases of 7.2%-22.3% in soil moisture, 8.9%-27.8% in ammonium nitrogen, and 11.0%-22.1% in nitrate nitrogen. The combined treatment of mulching and biochar application(CF and CBF)can increase soil temperature, while the single application of 2.5 t/hm² biochar has no significant effect on increasing soil temperature. Rice yield significantly correlates positively with soil water content, soil ammonium nitrogen, and nitrate nitrogen content(P<0.05). The CBF treatment achieves maximum economic benefits with 26.8% yield increase and 15.1% net income enhancement. Comprehensive evaluation reveals that the combined film mulching and biochar application represents the optimal management practice for irrigation paddy fields in this study. This research provides theoretical references for establishing appropriate film mulching and biochar application strategies in Heilongjiang paddy fields.

The physiological mechanisms underlying water saving and yield increase in spring maize production under subsurface drip irrigation compared with traditional border irrigation were investigated. A field comparative experiment of subsurface drip irrigation(DI)and border irrigation(BI)was conducted in spring maize fields on the south bank of the Yellow River irrigation area in Inner Mongolia. Soil moisture content, crop growth, and photosynthetic parameters were measured under both irrigation methods, and the differences of parameters among different treatments were analyzed. Results indicate that the shallow groundwater depth and high supplemental irrigation amount during the seedling stage result in relatively high soil moisture content under BI. In contrast, DI reduces the irrigation amount at the seedling stage and maintains soil moisture at 60%-90% of field capacity, which lead to better crop growth, photosynthetic physiology characteristics, and yield compared to BI. At maturity, DI increases plant height, stem diameter, leaf area, and aboveground dry matter weight by 12.9%, 10.2%, 327.0%, and 23.2%, respectively. During the bell and tasseling stages, DI improves the transpiration rate, net photosynthetic rate, stomatal conductance, leaf nitrogen content, and SPAD value by an average of 18.4%, 14.5%, 43.8%, 18.2%, and 9.5%, respectively. DI also significantly enhances the carboxylation rates of PEP carboxylase and RuBP carboxylase at the bell stage, and the grain yield under DI is 33.8% higher than that of the BI treatment. The study concludes that subsurface drip irrigation increases yield by maintaining soil moisture within a suitable range and increasing leaf nitrogen content, thereby improving photosynthetic capacity and promoting crop growth. The results provide a scientific basis for extending drip irrigation in the Yellow River irrigation area and supply parameters for simulating spring maize growth under this irrigation mode.

Existing biomimetic water harvesting methods encounter challenges such as high cost and poor environmental adaptability. By taking inspiration from the hydrophilic/hydrophobic composite microstructure on the back of a desert beetle, a water-collecting biomimetic surface with a superhydrophilic/superhydrophobic composite microstructure and its low-cost preparation method were proposed. This method culminates in the formation of a superhydrophilic/superhydrophobic composite microstructure surface on a glass substrate through the steps of coating a modified SiO₂ layer, mask magnetron sputtering a Ti film, and chemical etching to convert the Ti film into TiO₂ arrays. The surface exhibits the capacity to capture water mist through the superhydrophilic TiO₂ arrays, and accelerates the shedding of captured droplets through the superhydrophobic SiO₂-coated channels around the arrays to enhance the water collection efficiency. The experimental study demonstrates that the water collection rate exhibits a significant increase with an increase in mask plate mesh. At a mesh size of 500, the water mist collection rate can reach 3.455 g/(cm²·h). However, the surface exhibits susceptibility to corrosion in acidic environments, resulting in a decline in water collection performance. Conversely, in alkaline environments, the surface demonstrates enhancement in alkali resistance, thereby maintaining optimal water collection efficacy. The method is both low-cost and environmentally adaptable, providing a solid theoretical and experimental foundation for the application and promotion of water-collecting biomimetic surfaces.

In order to eliminate the additional water-dispersion devices required by some impact sprinklers under medium and low pressure, a jet impingement sprinkler was designed based on the asymmetric impact model between main and auxiliary nozzle. Hydraulic performance tests were conducted to obtain the water distribution and range of jet impingement and no-impingement sprinklers under medium and low pressure with different orifice diameter ratios(1.00, 1.33, 1.66, 2.00), and the combined uniformity coefficient was calculated. High-speed photography was used to capture jet images and measure variations in jet breakup length. Nonlinear curve fitting was applied to establish relationships among the orifice diameter ratio, diameter of the main nozzle outlet, jet breakup length, working pressure, and wetted radius. The results show that, compared with jet no-impingement sprinkler, jet impingement sprinkler exhibit a more gradual water distribution trend. As the uniformity of jet impingement combination improves, the wetted radius decreases. The jet breakup length increases with the increase of the orifice diameter ratio, confirming the phenomenon that the range of the hydraulic perfor-mance increases with the increase of the orifice diameter ratio. According to the comprehensive evaluation score, the jet impingement sprinkler with an orifice diameter ratio of 2.00 is suitable for medium and low-pressure irrigation. These findings offer a theoretical basis for research on asymmetric jet impingement sprinklers.