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.

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 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.

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.

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.

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.

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 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.

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 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 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.

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.

To explore the suitable water-nitrogen management mode for direct-seeded rice cultivation in Zhanghe Irrigation District, the ORYZA_V3 model was calibrated and validated by using field trial data of 2022 and 2023, and the calibrated model was used to analyze the impact of different hydrological years′ water-nitrogen modes on the yield and nitrogen use efficiency of direct-seeded rice. The Entropy-TOPSIS model was employed for comprehensive evaluation. The results indicate that the simulated values of total above ground biomass(WAGT), dry weight of stems(WST), dry weight of green leaves(WLVG), dry weight of storage organs(WSO), and leaf area index(LAI)are consistent with the 1∶1 line. Statistical analysis of the simulation results show that the determination coefficients R² range from 0.640 to 0.980, the normalized root mean square error(nRMSE)ranged from 11.48% to 33.48%, and the Nash coefficient(NSE)ranges from 0.03 to 0.96. Water-nitrogen scenario simulations show that yield and nitrogen utilization efficiency are at a high level when the lower limit of soil moisture before irrigation is 70% to 100% saturated soil moisture. The yield decreases when it is less than 70% saturated soil moisture. When the nitrogen application rate is greater than 205 kg/hm², there is no significant increase in rice yield, and the output efficiency of nitrogen is reduced. It is recommended that a water-nitrogen management mode in Zhanghe Irrigation District is nitrogen application level of 205 kg/hm² and its fertilizer ratio of base to tillering is 5∶5. For wet years, the lower limit of irrigation is 70% of the saturated soil moisture, and the lower limit of soil moisture before irrigation in the normal(50%)and dry year type(75%)is 80% of the saturated soil moisture.

For cotton drip irrigation in the typical area of northern Xinjiang, two irrigation limits were established at the budding stage: 60%-65% and 70%-75% of the field water holding capacity. Three irrigation limits were set at the bolling stage: 55%-60%, 60%-65%, and 70%-75% of field water holding capacity. A total of six treatments with different irrigation limits were designed by completely random design. The effects of different treatments on water and salt distribution, yield and its components and water use efficiency at different fertility stages of cotton were analyzed by using local conventional drip irrigation as the control. The results show that the salinity of the 0-50 cm soil layer increases the fastest after irrigation, and the higher irrigation lower limit has a better salt washing effect due to the reduction of the irrigation interval and the increase of the irrigation frequency during the cotton fertility period, which leads to better salt leaching effects. The desalination rate of the 0-80 cm soil layer ranges from 11.67% to 46.99% during the whole reproductive period, and the desalination rate first decreases and then increases as the increase of the irrigation limit. The desalination effect is optimal when the irrigation threshold is 70%-75% of the field water retention rate at both the bud and bolling stages. The average soil temperature in the 0-50 cm soil layer of all treatments increases by 0.06%-3.89% compared to that of CK, and there is a linear relationship between soil temperature and water content and salinity in the 0-50 cm soil layers. Increasing the lower limit of irrigation can help to enhance the diffusion of water and downward seepage of salts. The treatment that controls the lower limit of irrigation, compared with CK, increases yield and water use efficiency by 4.32% to 26.46% and 50.60% to 89.16%, respectively, which is beneficial for improving cotton water use efficiency and yield. A comprehensive analysis show that when the lower limit of irrigation is set to 70%-75%, field water holding rate at both bud and boll stage, the seed cotton yield is the highest at 6 946.65 kg/hm², which is 26.46% higher than that of the CK treatment, and the water use efficiency is 62.65% higher than that of the CK, achieving better water conservation, salt suppression and yield enhancement effects.

To enable timely crack detection in hydraulic turbine runner blades, ensure unit health monitoring, and enhance operational safety, an intelligent fault diagnosis method was proposed based on computational fluid dynamics(CFD), rime optimization algorithm(RIME), variational mode decomposition(VMD), and long short-term memory(LSTM)neural network. First, the flow field was simulated using CFD, and the results were imported into finite element analysis(FEA)software through fluid-structure interaction to obtain time-domain vibration signals for both healthy and cracked runner blades. Subsequently, the modal component number(K)and penalty factor(α)of VMD were optimized by RIME. The optimized VMD was then employed to decompose the vibration signals into multiple intrinsic mode components. Finally, these components were fed into the LSTM neural network for feature extraction and fault identification. The results demonstrate that the proposed method eliminates the economic costs associated with physical crack sample acquisition, significantly reduces the development cycle, and achieves highly accurate blade crack detection. For radial and axial vibration signals, the overall fault recognition accuracy reaches 93.033 0% and 92.893 9%, respectively.

To address the low accuracy of online pH detection in cultivation substrates, a TiO₂ electrode was fabricated by chemical etching and utilized as the working electrode in a pH sensor. An extended-gate field-effect transistor(EGFET)-based pH sensor and an online detection system were developed. The hardware consisted of a power supply circuit, an EGFET sensor circuit, a signal conditioning circuit, a voltage follower circuit, and a main control unit based on an STM32 microcontroller with ESP8266 Wi-Fi module. The software architecture included embedded firmware, an IoT cloud platform, and a mobile application for remote monitoring. Experimental results demonstrate that the EGFET-based sensor exhibits superior performance over conventional potentiometric methods, with improvements in response time, drift, hysteresis, and linearity. In validation tests using a cultivation substrate with 71.4% relative moisture content, the system achieves a maximum relative error of 2.63%, representing a 16.51% reduction compared to traditional methods. The proposed system enhances the accuracy and reliability of real-time pH monitoring in agricultural substrates.

The rotating cavitation characteristics of the inducer and its suppression techniques from the aspects of theoretical, experimental and numerical calculations were reviewed. On the theoretical aspects of rotating cavitation, the important key milestones in the development of relevant theories were sorted out. In the experimental aspects of rotating cavitation, the experimental research on related parameters such as flow coefficient, rotation speed and cavitation number were reviewed, and it is pointed out that the establishment of a multi-intergraded test platform can be more effective in obser-ving the characteristics of rotating cavitation. In the numerical calculation of rotating cavitation, the numerical simulation methods of inducer rotating cavitation developed in recent years were summarized. By analyzing and summarizing the research results of the rotating cavitation suppression technology, it is believed that changing the impeller inlet, blade tip clearance and blade load is a more effective way. Finally, the development direction of the inducer rotating cavitation characteristics and related suppression technology was prospected.

Aiming at the problem of valve closing water hammer caused by the closing of the end valve in the long-distance gravity flow high-fluctuation water conveyance system, a gravity flow water conveyance project in Xinjiang was taken as an example. The valve closing law without protective measures and the influence of its parameters on the water hammer pressure after the arrangement of the air tank were studied by numerical simulation method. The influence of the diameter, volume and water volume ratio of the air tank connecting pipe on the maximum pressure head were compared through orthogonal experiment and range analysis. The results show that when no protective measures are taken, the two-stage valve closing is better than the linear valve closing. The fast-closing time accounts for 30% of the total closing time and the fast closing angle is 85%, so the two-stage valve closing is the optimal valve closing method. When the total closing time is 100 s and 200 s, the maximum pressure head under the two-stage valve closing is 35.7% and 38.3% lower than that under the linear valve closing, respectively, but the negative pressure in the whole line is serious. The order of the influencing factors of redu-cing the maximum pressure head of the air tank from high to low is as follows: the diameter of the connecting pipe, the volume of the air tank, the proportion of the water volume. After selecting the optimal air tank parameters, the maximum pressure head reduces by 31.6%, and the minimum pressure head increases by 91.0%, which meets the protection standard.

To address the wear issues in low-specific-speed centrifugal pumps under high-volume fraction and large-size particle conditions, an experimental and numerical simulation combined approach was employed to investigate the wear characteristics inside the impeller. A test pump was designed for wear experiments, and the results reveal that the primary wear regions of the impeller are concentrated in the front section of the flow channel, including the first half of the pressure side of the blades, the first sixth of the suction side, the periphery of the rear shroud hub, the intersection area between the front shroud and the blades, and the flow channel inlet. Based on computational fluid dynamics(CFD), the solid-liquid two-phase flow was numerically simulated using the particle inhomogeneous flow model. The simulation results demonstrate that solid particles are unevenly distributed in the flow channel, with noticeable particle accumulation in the inlet region and a higher particle volume fraction near the pressure side of the blades. The impact angles of particles are larger in the front section of the impeller flow channel but smaller in the rear section. By combining the vector cross-product principle to extract particle impact angles, the Oka wear model is integrated with the Eulerian-Eulerian method, enabling accurate prediction of impeller wear under high-volume fraction and large-size particle conditions. The predicted results show good agreement with experimental data, providing a theoretical foundation and engineering reference for the anti-wear optimization design of low-specific-speed centrifugal pumps.

In order to improve the internal flow characteristics of centrifugal fans and mitigate aerodynamic noise, an investigation was conducted on centrifugal fans with different blade trailing edges. Specifically, three different configurations with trailing edge of circular, circular-cut and elliptical were designed, all derived from a baseline square trailing edge model. The performance metrics, flow field distributions, and pressure pulsation of different models were analyzed through numerical simulation. Utilizing the Lighthill acoustic analogy theory, the influence of blade trailing edge geometries on the aerodynamic performance and acoustic characteristics of centrifugal fans was studied. The results show that there is a significant increase in total pressure and efficiency of the three blade trailing edge models under design condition, which are higher than those of the prototype model. The elliptical trailing edge model has the largest increase in total pressure and efficiency, increasing by 4.7% and 1.1%, respectively. The pressure pulsation amplitude observed in the three modified models is lower than that of the prototype model, and the elliptical trailing edge model exhibits the largest pressure pulsation reduction. The acoustic field calculation results show that the noise of centrifugal fan with circular trailing edge and circular trailing edge model decreases by 1.50 and 1.79 dB, respectively. Notably, the elliptical trailing edge model exhibits the best acoustic performance, and the noise value decreases by 2.10 dB. The aforementioned results show that a reasonable modification of the blade trailing edge geometry can effectively improve the internal flow conditions of a centrifugal fan, thereby reducing flow losses, increasing the efficiency and diminishing the aerodynamic noise.

In order to analyze the impact of guide vanes with varying degrees of cavitation erosion on the internal flow field of a Francis turbine, based on the HLA855a-LJ-250 turbine, four models were established corresponding to the different stages of cavitation erosion development on the movable guide vanes namely: intact, dotted, honeycomb, and continuous flake cavitation pits. The unit operated under rated operating conditions, and steady-state calculations were performed using the Realizable k-ε turbulence model and wide-band noise model. The results indicate that as the degree of cavitation erosion in the guide vane increases, the value and range of turbulent kinetic energy of guide vane components gradually increase. Water flow impact and friction within cavitation pits are significant factors contributing to energy dissipation. The negative pressure of the runner in the unit with cavitation erosion is lower, making the runner more susceptible to cavitation erosion. This also leads to disordered draft tube streamlines, which significantly hinders energy recovery and utilization. The severity of cavitation erosion is inversely proportional to the recovery efficiency. The more severe the cavitation erosion, the lower the recovery efficiency. Additionally, the degree of cavitation erosion is closely related to the sound intensity of the guide vane parts. This correlation is further manifested as a positive relationship where both the value and distribution range of sound pressure level increase with cavitation severity. The research findings offer guidance and assistance for monitoring the condition of the unit.

The lateral layouts and preset concentrations of fertilizer solution are important factors affec-ting the system uniformity performance of the applied water and fertilizer. Field experiments were conducted to evaluate the effects of lateral layout and fertilizer solution concentration on fertigation performance at the irrigation subunit and rotation group scales. Two methods were considered for pipeline layout: 45 m and 90 m(denoted S45 and S90, respectively)capillary and one dual-ends water fee-ding modes with lateral length of 90 m(denoted as D90)were considered. Fertilizer solution concentrations(mass fraction of fertilizer)were set at three levels: 0.181%, 0.091%, and 0.060%(denoted as C1,C2,C3,respectively). The results demonstrate that compared with single-end water feeding mode, the dual-ends water feeding mode reduces the pressure head deviation by 26.1% to 32.0%, and reduces the pressure head deviation rate of the rotational group by 27.2%. The emitter discharge deviations observed are generally less than 20% in the subunits, which are less affected by the pressure head imbalance among the subunits. However, the emitter discharge deviations in the rotation group remain approximately 30%. The dual-ends water feeding mode significantly improve the uniformity of the water and fertilizer applied at the rotational irrigation group scale, while a relatively decrease in fertilizer solution concentration benefits the uniformity of the applied fertilizer. It is recommended to choose dua-lends water feeding mode in drip irrigation systems, and to increase the duration of fertilizer application when the total amount of fertilization applied has been determined in order to attenuate the negative impact of high fertilizer concentration on the uniformity of fertilizer application.

Taking the spiral groove high-temperature liquid dynamic pressure mechanical seal as the research object, a stochastic rough surface model of the sealing end face conforming to a Gaussian distribution was established based on the autocorrelation function method, along with a two-phase vapor-liquid flow calculation model. The influence of roughness at different locations on the end face on the vaporization characteristics and sealing performance of the lubricating film was then simulated and analyzed. The results indicate that when the end face is rough, the vaporization region of the lubricating film is mainly concentrated in the groove-dam area, with the highest degree of vaporization occurring in the inner groove region of the spiral groove. End face roughness causes the isolines of the average vapor volume fraction in the lubricating film to exhibit irregular wavy patterns, which become more pronounced with increasing roughness. The average vapor phase volume fraction of the lubricating film decreases with increasing end face roughness, while the opening force increases with greater end face roughness. Additionally, the leakage rate through the sealing gap decreases as the end face roughness increases. The influence of roughness at various locations on the vaporization characteristics and sealing performance exhibits a cumulative effect when the entire end face is rough. The impact of unit roughness at different locations on the vaporization characteristics of the lubricating film and sealing perfor-mance follows the order from largest to smallest: roughness in the non-groove area of the dynamic ring, roughness on the end face of the static ring, and roughness in the groove area of the dynamic ring.

To address the challenges of large computational scale, time-consuming analysis, and high costs associated with unsteady flow field calculations in pump-jet thrusters under navigation conditions, a flow field prediction framework was developed using two machine learning methods: recurrent neural network(RNN)and long short term memory(LSTM). Time-series data of the pump-jet tail jet flow field at a navigation speed of v=2.91 kn were obtained through numerical methods. Sample sets were constructed, and the prediction framework was trained to perform unsteady periodic predictions of the pump-jet tail jet flow. The results demonstrate that the determination coefficients(R²)of both prediction frameworks exceed 0.995 0, with mean absolute errors(MAE)below 0.079 0 and root mean square errors(RMSE)under 0.089 0. The computational time per training epoch does not exceed 40 s for the RNN model and 115 s for the LSTM model, respectively. The machine learning approach based on RNN and LSTM neural network prediction models proves capable of accurately and efficiently predicting the complex unsteady flow characteristics and spatial distribution patterns of the pump-jet tail jet flow. Furthermore, the two models exhibit distinct predictive accuracies for different variables during long-term and short-term forecasting. The RNN model demonstrates superior efficiency and higher accuracy for short-term predictions, while the LSTM model exhibits enhanced predictive capability for long-term forecasting.

In order to improve the comprehensive performance of axial flow pump, on the basis of experimental verification of the accuracy of numerical calculations, the inverse problem design method was adopted. Taking the efficiency and head under the design condition as optimization objectives, combined with the orthogonal experimental design method, the multi-objective optimization of vertical axial flow pump with the specific speed of 1 321 was carried out. The research results show that the geometric parameters(the number of blades B, the leading edge flange position L_s of the blades, and the trailing edge flange position T_s of the blades), and the loading parameters(the leading edge load value L_Es of the blades at the flange, the leading edge load value L_Eh of the blades at the hub, and the slope K_h of the middle straight line at the hub), all have a significant influence on the energy characteristics of the axial flow pump.The hydraulic efficiency and head of the optimized axial flow pump model are 85.58% and 4.356 m, respectively, which are 1.36 percentage points and 0.877 m higher than that of the original model. The more uniform flow field in the optimized model impeller is the fundamental reason for its performance improvement. This study can provide guidance for the design optimization of similar type of axial flow pump.

To investigate the effect of low volume concentration of sand conditions on the cavitation characteristics of hydrofoil, a modified RNG k-ε turbulence model and SIMPLEC algorithm were used. Based on the discrete phase model and Schnerr-Sauer cavitation model, the unsteady cavitation flow around NACA0015 hydrofoil under low volume concentration and coarse-grained sand conditions was numerically simulated. The effects of particles of different volume concentrations and diameter sizes on the cavitation flow field of hydrofoil were analyzed to reveal the mechanism of particle action on cavitation development. The results indicate that increasing the particle volume concentration at the same particle size and increasing the particle diameter at the same volume concentration result in an increase followed by a decrease in the lift coefficient of the hydrofoil. The effect of solid-phase on the drag coefficient of the hydrofoil has a smaller effect, in which the particle diameter has a greater effect on the lift-to-drag ratio of hydrofoil. Compared with the clear water condition, the hydrofoil cavitation bubble shedding position is closer to the leading edge of the hydrofoil and the shedding time is shorter. With the increase of particle volume concentration and particle diameter, the volume of the cavitation bubble first decreases and then increases. The influence of the particles on the development of cavitation is first inhibited and then facilitated. The cavitation flexibility of the hydrofoil varies between positive and negative for both clear water and sandy conditions, with the intensity of the cavitation flexibility fluc-tuations increasing and then decreasing as the particle volume concentration increasing.