To address prevalent issues related to water resource wastage and the limited scope of irrigation and drainage planning and design in contemporary agricultural irrigation regions, and to effectively advance the standardization of the design process for irrigation and drainage planning, a theoretical study on agricultural adaptation was undertaken. This study was grounded in the specific context of the rice irrigation area in Yaoqiao Town, Zhenjiang City, Jiangsu Province, utilizing a bidirectional flow channel pumping station as a case study. The feasibility and effectiveness of bidirectional flow channel pumping stations mainly applied to large and medium-sized water conservancy facilities in agriculture were explored. A water supply and drainage planning and design mode suitable for rice agriculture in this irrigation area were given, and a suitable irrigation and drainage design and planning program was given. Two neighboring paddy fields were selected for actual planting comparison, with ordinary pumps and bidirectional flow channel pumping stations for irrigation and drainage operations, respectively. The results of irrigation and drainage experiments show that the bidirectional flow channel pumping stations planning in paddy fields can increase the yield of rice under each growth cycle by 4.76%. Compared with ordinary pumps, the power energy of the pump station can save 7.2% in electricity, achieving a comprehensive water-saving effect of 12.2%. The average integrated benefits of the paddy fields served per hectare increase by more than 3 420 yuan. Significant emphasis is placed on the critical role of preparatory work prior to the planning and design of irrigation and drainage systems. Utilizing a comprehensive assessment of the project area, a scientifically grounded and rational design analysis is performed for the irrigation and drainage engineering.

Focusing on the Fengle River Irrigation District in Jiuquan City, Gansu Province, a refined spatiotemporal canal water distribution optimization model based on the WEAP model was developed, which was achieved by selecting a representative hydrological year, conceptualizing the irrigation district′s water distribution infrastructure, accurately identifying the irrigation district′s cropping patterns, and determining crop water requirements for different irrigation control areas. The model′s objective function minimized irrigation water deficits. Considering crop spatial distribution and water requirements during each growth stage, six different canal water distribution priority schemes were selected and compared to analyze the resulting water allocation process and irrigation benefits. The results indicate that, in an extremely dry representative hydrological year, the mismatch between the irrigation district′s traditional water distribution practices and actual crop water needs is significant, leading to yield reductions in areas with lower water distribution priority. Prioritizing water allocation to crops with higher water demand, while ensuring adequate ecological flow in the river, results in a higher degree of coupling between water distribution priority and crop water needs, leading to more rational water allocation. A water distribution scheme prioritizing the irrigation of maize-growing areas within the district achieves both equitable irrigation benefits and higher crop yields and economic returns, exceeding the average yield of other schemes by 6.9% and the average economic benefits by 10.5%. The water deficit rate deviation among canals with the same priority order is only 0.067, which is superior to the 0.163 and 0.164 deviations observed under the irrigation district′s traditional single-year and two-year priority schemes, respectively. The findings provide important technical guidance for improving water resource utilization efficiency and benefits in irrigation districts.

In order to study the effect of flow conditions on the hydraulic performance of bulb pump systems, computational fluid dynamics methods were used to numerically calculate the unsteady flow characteristics inside bulb pumps under uniform and non-uniform flow conditions. The velocity distribution data were extracted from the outlet section of the inlet passage in the pump station as the non-uniform inflow conditions of the model pump, and the uniform inflow was compared. Based on the N-S equation and SST turbulence model, the unsteady flow behavior under multiple working conditions in the bulb tubular pump was simulated. The hydraulic losses and flow fields characteristics of the model pump system under different inflow conditions were analyzed by using the method of entropy generation and pressure fluctuation. The results show that the given non-uniform inflow conditions will cause non-uniformity flow in the impeller and diffuser domains, reducing the hydraulic performance of the pump systems. Based on the comparative analysis of total pressure loss and entropy production loss, it is found that the entropy production analysis method can evaluate the hydraulic performance of flow components. The energy loss mainly cover turbulent entropy production and wall entropy production. The effect of single grid volume on the local power loss area were visualized and quantified with entropy production theory. Through the pressure pulsation characteristics analysis, it is found that the non-uniform inflow conditions does not change the original amplitude frequency characteristics of the cross flow pump systems, but it will increase the fluctuation amplitude, which is not conducive to the stable operation of the pump device systems.

This study systematically investigated the force characteristics of a large two-stage double-suction horizontal condensate pump under different operating conditions by integrating the operational requirements of a specific power plant with a method that encompasses optimized design, three-dimensional flow field simulation, and experimental validation. Firstly, the reliability of the numerical analysis method and the accuracy of the optimization design parameters were verified through comparative assessment of numerical calculations and experimental tests. Secondly, unsteady numerical simulations were conducted to analyze the flow field variations and force characteristics of the two-stage double-suction horizontal condensate pump under normal, transient, and startup operating conditions. The findings indicate that the point of minimum pressure within the flow passage of the first-stage impeller is situated at the rear side of the blade inlet, and the region of low pressure is notably confined. This indicates that the impeller exhibits strong cavitation resistance. The axial and radial forces of the primary and secondary impellers were calculated and analyzed under transient and startup conditions. It is found that the maximum axial and radial forces of the primary impeller are 3 148.546 N and 4 642.354 N, respectively. In comparison, the maximum axial forces and maximum radial force of the secondary impeller are 2 132.887 N and 5 906.412 N, respectively. All recorded force values meet the design requirements, indicating that the condensate pump is capable of maintaining safe and stable operation requirements under various working conditions, thereby achieve the expected design objectives.

This study aims to minimize agricultural irrigation water consumption, maximize grain crop yield and crop economic benefits, and minimize regional water distribution differences. Based on the degree of future water-saving measures in the irrigation area, multi-objective optimization models for allocation of agricultural water and land resources were constructed at the branch canal scale under four irrigation scenarios: current level, channel seepage prevention, pipeline water delivery, and water-saving irrigation. The NSGA-Ⅲ algorithm was used to jointly optimize the crop planting area and irrigation water volume in the Fengle River irrigation area, which is a typical oasis irrigation area in the Hexi Corridor. The research results indicate that the optimized allocation of agricultural water and land resources at the branch canal level includes more regional characteristics and spatiotemporal constraints, which can provide a refined water allocation and planting structure adjustment plan based on different preferences of the Pareto solution set for the decision-making process. Agricultural irrigation water consumption positively correlates with grain crop yield and crop economic benefits. For every 10 000 m³ increase in irrigation water consumption, the optimization screening process tends to increase grain yield by an average of 6 954 kg or economic benefits by an average of 27 400 CNY. With the implementation of different degrees of water-saving measures, pipeline water transportation and water-saving irrigation can release 7.8×10⁶ m³ and 1.1×10⁷ m³ of agricultural irrigation water, with water-saving benefits of 135 and 190 CNY/hm², respectively. At the same time, both show an increase of about 8.1% in grain crop yield targets, and regional water distribution differences decrease by more than 1 500 m³/hm². The research results can provide theoretical basis and technical support for optimizing planting structure, improving water and land resource utilization efficiency and benefits in arid oasis irrigation areas.

To investigate the fault characteristics of vertical submersible pumps under bearing wear conditions, a multi-source condition monitoring system was established, and bearing fault samples were processed and selected. Fault experiments were conducted to collect voltage, current, vibration, and temperature signals of the submersible pump under various operating conditions. The time-domain and frequency-domain characteristics of these signals were then analyzed. Typical fault samples were created by customizing bearings with increasing clearance and selecting service-failed bearings. A comprehensive testing platform was established, which included an electrical signal monitoring system above ground and a mechanical signal acquisition device underground. The experimental system synchronously collected multi-source signals such as three-phase voltage and current, radial and axial vibrations, motor temperature, and outlet pressure, covering a flow range of 20% to 160% of the rated capacity. The results indicate that the characteristics of the customized faulty bearings and the service-failed bearings are similar across various signals. Notably, the vibration signal characteristics are pronounced, with an increase in the peak-to-peak value of the vibrations. The amplitude of the radial vibration at the rotational frequency significantly increases, while the axial vibration shows an increase in the harmonics of the rotational frequency. In terms of the current signal, there is a modulation effect observed at four times the rotational frequency.

To evaluate the effect of different nitrogen fertilizer application patterns on the yield and quality of spring tea, the ″Maolv″ tea cultivar was selected as the experimental object. The distribution ratios of nitrogen fertilizers in the autumn, spring and summer stages, namely T1, T2 and T3, were established as 5∶3∶2, 6∶2∶2 and 4∶3∶3, respectively. Four nitrogen application amounts, namely N1, N2, N3 and N4, were set as 300, 375, 450 and 525 kg/hm², respectively. Twelve treatments combinations were designed and compared with the conventional treatment in the tea garden as the control(CK)to assess fertilization efficacy. The effects of different treatments on spring tea yield(measured by hundred-bud weight)and quality parameters(including tea polyphenols, amino acids and the ratio of polyphenols to amino acids)were systematically analyzed. The results show that when the proportion of nitrogen application in autumn is not less than 50% of the total nitrogen application, the mass of hundred-bud quality reaches its maximum of 13.04 g when the total nitrogen application amount increases to N3(450 kg/hm²). Further increasing the total nitrogen application, however, results in a decrease in the mass of hundred-bud quality. Simultaneously, as the increase of the total nitrogen application amount, the content of tea polyphenols decreases to some extent, while the content of amino acids increases. At N3 level, the mass ratio of tea polyphenols decreases to the lowest of 176.49 mg/g, and the mass ratio of amino acids increases to the highest of 25.22 mg/g. When the nitrogen fertilizer distribution ratio remains constant, the mass of hundred-bud quality initially increases and subsequently decreases as the increase of the total nitrogen application amount. Conversely, when the total nitrogen application amount is constant, the comprehensive effects of both yield and quality reach the best under the T2 distribution ratio level, with the minimum ratio of tea polyphenols to amino acids being 7.00. Based on these findings, the recommended optimal fertilization scheme is as follows: the distribution ratio of nitrogen fertilizers in the autumn, spring and summer stages is 6∶2∶2, and the total nitrogen application amount should be 450 kg/hm².

To address the issues with the bolted connections on the end cover of the inlet check valve of the diaphragm pump in the iron concentrate slurry transportation pipeline, a three-dimensional model of the check valve and a solid-liquid two-phase flow model of the slurry were established. Using the fluid-structure interaction method, the load spectrum on the end cover and the stress conditions of the bolts at different opening degrees of the valve core were analyzed. On this basis, the genetic optimization algorithm was applied to conduct the layout optimization design of the bolts on the check valve end cover. The optimized layouts of bolts with different performance grades were obtained, and the effectiveness of the optimization results was verified. The research results show that when the performance grade of the bolts is maintained at grade 12.9, the number of bolts can be increased from the original 8 to 10, the diameter of each single bolt can be reduced by 6 mm, and the total volume of the bolts can be decreased by 8.2%. This achieves a lightweight design and reduces the stress on each single bolt. If the current number and diameter of the bolts remain unchanged, the performance grade of the bolts can be reduced to grade 10.9, which effectively reduces the production cost and is also the most easily implementable technical improvement plan. The research results can provide a certain basis for the upgrade and improvement of the check valve and have important engineering application value in terms of lightweight design and cost control.

In order to investigate the effect of pre-corrosion time on cavitation, the leaded brass was immersed in seawater for different times of pre-corrosion and these sample was used to test cavitation by ASTM G32 ultrasonic cavitation experiment. The comprehensive analysis was conducted on the structure, composition of the oxide films formed on the surface of leaded brass under different pre-corrosion time conditions. The results show that oxidation products change as corrosion time increases. After pre-corrosion 240 h, oxidation film with Cu₂O and ZnO as the main components is formed. After pre-corrosion 480 h, part of the Cu₂O is converted to Cu₂(OH)₃Cl. And after pre-corrosion of 720 h, the oxidation film is mainly composed of Cu₂O and NaZn₄Cl(OH)₆SO₄·6H₂O. The prolonged corrosion time increases the continuity of the film, weakens the ability to exchange ions between the specimen and seawater, and thus improves the corrosion resistance of lead brass. Furthermore, the preferentially formed film can alleviate the impact of cavitation bubble collapse on the specimen surface. With the extension of pre-corrosion, the mass loss of the specimen is reduced. With cavitation in the seawater for 1 h, the mass loss of the pre-corrosion 720 h specimen is about half that of non-pre-corrosion specimens, de-monstrating that the resistance to cavitation of the specimen is improved.

To elucidate the impact mechanism of post-drought rehydration on the photosynthetic cha-racteristics and yield of wheat leaves under different nitrogen application levels, a field experiment was conducted to investigate the effects of three nitrogen application rates(N₁: 100 kg/hm²,N₂: 200 kg/hm²,N₃: 300 kg/hm²)under well-watered conditions(W₀, irrigation threshold set at 75% of field water-holding capacity)and post-drought rehydration conditions(W₁, irrigation threshold set at 55% of field water-holding capacity)on the net photosynthetic rate, light response characteristics, and yield of winter wheat. The results indicate that under well-watered conditions, the net photosynthetic rate(Pn), light response curve, and related light response characteristic parameters increase with the rise in nitrogen levels. Under post-drought rehydration conditions, Pn, light response curve, and related light response characteristic parameters show an initial increase followed by a decrease with the increa-sing nitrogen levels. Specifically, during the jointing stage, the post-drought rehydration treatment exhibits a 5% increase in yield under the N₂ nitrogen level compared to the well-watered treatment. This suggests that post-drought rehydration coupled with 200 kg/hm² nitrogen application during the jointing stage can quickly restore the photosynthetic system of leaves and enhance the photosynthetic potential of winter wheat leaves. Therefore, at a nitrogen application rate of 200 kg/hm², the impact of post-drought rehydration on the photosynthetic characteristics and yield of winter wheat leaves is minimal. This research provides theoretical support and technical guidance for implementing water and nitrogen optimization management strategies for winter wheat in arid and semi-arid regions.

In order to investigate the effects of different irrigation moisture content on the quality of sea buckthorn, field experiments were conducted at the 170th Regiment of the Ninth Division of the Xinjiang Production and Construction Corps. The study focused on the locally dominant variety, with five water gradients established. The fruit quality indexes were measured, and the principal component analysis method was applied to investigate the effect of different irrigation moisture on sea buckthorn quality, and a comprehensive evaluation model was constructed to select the optimal moisture treatment. The results show that among the 10 quality indexes under five moisture gradients, the effect of irrigation moisture has a significant effect on the vitamin C content of sea buckthorn. Increasing irrigation during the flowering and fruiting periods significantly improves the weight of a hundred fruits and the fruit′s longitudinal and transverse diameters. The appropriate reduction of irrigation moisture content during fruit expansion and fruit ripening does not negatively affect the nutritional quality of sea buckthorn. With the decrease in irrigation moisture, the total amount of sugar, vitamin C, and soluble solids increase, while the total acid content decreases. The cumulative contribution of the three principal components extracted from the principal component analysis reaches 98.573%. The calculated score from the comprehensive evaluation model indicates that treatment W3(irrigation quota 450 mm)is the optimal water treatment. The results of this study can provide a reference basis for the large-scale plan-ting of sea buckthorn.

To evaluate the impact of different water and nitrogen coupling strategies on the physiologi-cal growth of drip-irrigated grapes in the Turpan-Hami region of Xinjiang, ″Seedless White″ grapes were selected as the experimental material, employing two factors: irrigation levels and nitrogen application rates. The irrigation treatments included full irrigation(D0), mild regulated deficit irrigation during shoot growth(D1), and moderate regulated deficit irrigation(D2). A total of nine experimental treatments were implemented, comprising conventional nitrogen application(N0), a 10% reduction in nitrogen application rate(N1), and a 20% reduction in nitrogen application rate(N2), with each treatment replicated three times. The control treatment(CK)was managed according to conventional practices within the park(D0N0). Additionally, a two-factor completely randomized block design experiment was employed. The results reveale that, in comparison to the traditional water and nitrogen management(CK), the application of mild deficit irrigation combined with 270 kg/hm² nitrogen(D1N1)results in a reduction in the relative water content and intercellular CO₂ concentration in grape leaves. However, this treatment leads to an increase in leaf area index, net photosynthetic rate, transpiration rate, and stomatal conductance. The grape yield for the D1N1 treatment is 31 132 kg/hm², which does not differ significantly compared with the CK treatment. Nonetheless, the irrigation water use efficiency improves by 10.25%, and the partial factor productivity of nitrogen increases by 10.78% relative to the D1N1 treatment. In addition, path analysis shows that the leaf area index, net photosynthetic rate, and transpiration rate directly influence grape yield, while the relative water content, stomatal conductance, and intercellular CO₂ concentration are indirect factors. In summary, the combination of mild deficit irrigation and 270 kg/hm² nitrogen application proved to be the optimal strategy is the best under the experimental conditions, maintaining stable yields and saving 10% of both in water and nitrogen resources.

In order to further improve the heat dissipation performance of oil-free scroll compressor air-cooled system, the profile, cross-section and size of the heat dissipation fins were optimized. On the basis of Bessel curve, a new fin profile was constructed, and the cross-section of the fin with good coo-ling effect was determined. Then the influence of each size of the fin on the heat dissipation was further studied by orthogonal test, and the optimal size combination was determined. The results show that the heat transfer performance of the fin profile based on the Bessel curve is better. Rectangular cross-section has better heat dissipation effect in current special heat dissipation structures. The significant order of influence on average temperature in solid domain is fin spacing, fin thickness, and the significant order of influence on inlet and outlet pressure drop is fin spacing, fin thickness. The optimal size combination is 3.0 mm for fin spacing and 3.5 mm for fin thickness obtained by orthogonal test. After optimization, the average temperature of scroll disk is reduced by 15.88%, significantly improving the heat dissipation performance of the air-cooled system, and providing a reference for the research of the heat dissipation fins of the air-cooled system of oil-free scroll compressor.

In order to optimize the flow channel structure of toothed labyrinth flow channel emitter, CFD numerical simulation method was used to simulate the solid-liquid two-phase flow numerical calculations on toothed labyrinth emitters with back surface tooth angles of 0°, 10°, 19°, 30° and 45°, and the differences of flow velocity, turbulent kinetic energy, vortex distribution and particle trajectory in the flow channel under different tooth angles of back water surface were studied. The results show that the flow index and the discharge coefficient of the labyrinth emitter are positively correlated with the tooth angle of the back water surface, the hydraulic performance is the best when the tooth angle of the back water surface is 0°. As the tooth angle of the back water surface increases, the flow velocity in the emitter flow channel decreases as a whole, and the turbulent kinetic energy intensity increases. Through the Ω vortex identification, it is found that with the increase of the tooth angle of the back water surface, the area of the vortex motion area in the flow channel decreases and the intensity decreases. The longest particle residence time in the flow channel of the five kinds of back water surface tooth angles is 1.92, 3.77, 4.37, 0.87, 0.82 s, respectively. The emitter′s anti-clogging performance is optimal when the tooth angle of the back water surface is 45°. The simulation results show that the performance of the emitter can be improved by changing the tooth angle of the back water surface and adopting the form of an asymmetric flow channel.

In order to study the oxygenation performance of inverted umbrella aerators under the synergistic influence of different blade deflection angles, aerator impellers with the same number and shape of blades but different radial deflection angles and axial deflection angles were manufactured, and the oxygenation performance of four different types of inverted umbrella aerator impellers were compared. The results show that under the test conditions, there exists a positive correlation between the motor power, standard oxygenation capacity SOC, and dynamic efficiency E_S of the inverted umbrella aerators. For impellers with the same blade shape but different radial deflection angle and axial deflection angle, SOC and E_S of the inverted umbrella aerator show significant differences. When the motor load is low at 75 r/min, the impeller(type 1#)with no radial deflection angle and no angle of attack possesses the maximum SOC and E_S, which are approximately 3.81 kgO₂/h and 1.51 kgO₂/(kW·h), respectively. When the motor is running at almost full load, the impeller with certain radial deflection angles(type 2#)possesses the best SOC and power efficiency E_S, which are approximately 5.27 kgO₂/h and 1.82 kgO₂/(kW·h), respectively. In practical applications within wastewater treatment plants, one constant-speed inverted umbrella aerator and several variable-frequency inverted umbrella aerators are generally configured. To achieve the goal of energy conservation and reduced operational costs, it is recommended to use an impeller of type 2# with a certain radial deflection angle for the constant-speed inverted umbrella aerator, and an impeller of type 1# without radial deflection angle and angle of attack for the variable-frequency inverted umbrella aerator.

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.

To explore the effects of varying brackish water irrigation quantity and mineralization levels on the soil water with different salt distribution and yield of Lycium barbarum root layer, a two-factor field experiment was conducted in the Sanhuhe irrigation area, which is located downstream of the Hetao Irrigation District. Three irrigation levels were established at 210(W1), 300(W2), and 390 mm(W3), respectively. Additionally, four different salinity levels(2(S1), 3(S2), 4(S3), and 5 g/L(S4))were set, respectively. Fresh water irrigation with a mineralization degree of 0.608 g/L was used as the control group. The results show that under the condition of the same irrigation amount, the soil moisture content initially increases and then decreased with the increase of salinity, peaking at S2 level. All brackish water irrigation treatments lead to salt accumulation. When the irrigation amount is low, salt accumulation is evident in the profile. As the irrigation amount increases, there is an increasing trend in salt accumulation in the depth. In brackish water irrigation treatment, the W2S1 has the highest yield. Over the two-year period, the average fresh fruit yield reaches 16 593.85 kg/hm² and the dried fruit yield is 4 448.38 kg/hm². The simulation results show that the optimal brackish water irrigation volume is 334.90 mm and the salinity degree is 2 g/L in the lower reaches of Hetao Irrigation District.

In order to study the morphological change of near-wall single bubble and the accompanied energy effects, a finite element numerical model was established. The influences of dimensionless distance, initial radius and inner contents on the bubble dynamics were analyzed. After deriving and solving the bubble collapse energy governing equation, the characteristics of water kinetic energy and bubble potential energy over time under different conditions were obtained. The results show that the near-wall bubble morphology changes are influenced by dimensionless distances, initial bubble radii, and the composition of the bubble contents. The smaller the dimensionless distance, the longer the time required for the bubble to reach its maximum radius, while the influence of the initial radius on these parameters is opposite. In addition, the type of atmosphere inside the bubble exerts different effects on the total time of bubble collapse, due to different physical properties of the gases, including the solubility, molecular volume, etc. Under different conditions, the variation trend of kinetic energy in liquid area is basically the same, showing a downward parabola with three parts. Except for the slight fluctuation in the initial stage of bubble growth, the general trend of bubble potential energy change is firstly increased and then decreased, in which the dimensionless distance has the least effects. The research method in this paper provides a reference for the study of emitted energy for near-wall cavitation bubbles.

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.

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.

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.

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.

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.

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.

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.

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.

For rapid nondestructive detection of chlorophyll and nitrogen content in lettuce canopy leaves, hyperspectral imaging technology was used to collect hyperspectral images of lettuce canopies. The spectral reflectance of lettuce canopy leaves was analyzed in relation to chlorophyll and nitrogen content. The threshold segmentation method was used to remove background noise from the hyperspectral images. First-order differentiation preprocessing was applied to the spectral reflectance, and competitive adaptive reweighted sampling(CARS), successive projections algorithm(SPA), and a combination of CARS and SPA algorithms(CARS-SPA)were used to extract spectral characteristic bands of chlorophyll and nitrogen. A partial least squares(PLS)model was constructed. The results reveal that the best dimensionality reduction effect is achieved with the CARS-SPA algorithm, while maintaining key information. The number of bands used for modeling chlorophyll and nitrogen is reduced to around 19 and 20, respectively, both decrease by approximately 10%. Most of the repeated bands extracted using this method are concentrated in the first 10 bands of visible light and the near-infrared shortwave part, which shows strong correlation with lettuce chlorophyll and nitrogen. The PLS prediction model established using the CARS-SPA algorithm performs best, with determination coefficients(R²)of 0.767 7 and 0.696 8 for chlorophyll and nitrogen content prediction models, respectively, whose root mean square errors(RMSE)are of 1.559 5 and 0.765 2, respectively.