A comprehensive evaluation of a clinical ventricular assist pump(C pump)was conducted to systematically analyze its hydraulic performance, internal flow field characteristics, shear stress distribution, and thrombosis risks using a combination of experimental and numerical calculation methods. The results identifiy that the regions of vortex flow between the blades and local high shear stress may lead to a higher risk of thrombosis. Under the rated operating conditions, the vortex occurs mainly in the blade outlet region. As the flow rate decreases, the vortex flows may expand with a larger size and partially obstruct the impeller passage. The maximum scalar shear stress of 91.5 Pa, occurs at the blade outlet. This location corresponds to the site of maximum wall shear rate in the main vortex flow region predicted by the simulation and also matches the location where thrombus formation was observed. The findings reveal the inherent link among the complex flow patterns, high shear stress, and thrombosis formation. The blood test showed that the numerical results of the standard hemolysis index(NIH)was in agreement with the experimental results, which further confirms the validity of the numerical simulations. These insights are helpful for improving the optimized design and safety improvement of the ventricular assist devices to mitigate thrombosis risks.

To study the cavitation flow characteristics of a centrifugal pump with inducer under different flow conditions, numerical simulations were performed using the SST k-ω turbulence model and the Zwart-Gerber-Belamri cavitation model. The results show that the cavitation performance curve is flatter under high flow rate conditions compared to other flow conditions. With the decreasing of NPSHA(net positive suction head available), cavitation bubbles extend from the leading edges of the inducer and the impeller blades to the trailing edge. When severe cavitation occurs, cavitation bubbles fill the channel of impeller, resulting in a sharp drop in the head. The distribution of low static pressure area on the blades of inducer and impeller corresponds to the distribution of cavitation bubbles. At high flow rates, the angle of attack formed by the inflow direction and the inducer blade changes from positive to negative. This results in the static pressure on the pressure side not being significantly higher than that on the suction side. Consequently, cavitation bubbles in the inducer channel only appear at the leading edge of the pressure side under high flow rate conditions. As cavitation deteriorates, the flow field within the pump becomes highly disordered. Large vortices emerge in the middle section of the impeller and volute at low flow rate. With the increase of flow rate, the vortices become smaller. Due to the influence of the volute structure, the entropy production is larger at the tongue and the upper volute section near the tongue.

Pump as turbine(PAT)is widely used in energy-consuming industrial processes and micro-hydro power generation. As a kind of energy-saving equipment and micro-hydropower utilization device, PAT has the advantages of simple structure, low operation, and maintenance cost. Pump reversal operation is often accompanied by vibration and noise problems, and the stability of operation has been widely considered by scholars at home and abroad. A lot of research results have been obtained around the unsteady flow characteristics of PAT. A review was conducted on the research of PAT unsteady flow characteristics. Firstly, the existing achievements of PAT unsteady flow characteristics methods were summarized from experimental study and numerical simulation. Secondly, the research results on the operating characteristics of PAT unsteady flow were analyzed, especially focusing on PAT microscopic flow conditions and patterns. The results showed that the operational stability, mechanical characteristics of PAT and transient characteristics interacted with each other. Among these, the effect of rotor-stator interaction(RSI)on the three characteristics within a certain flow rate was one of the important factors. Finally, to provide a reference for the subsequent research on PAT, the prospect and future tendency of research on PAT was proposed, in which the experimental research methods. Co-optimized design of flow passage components, physical parameters of the working medium and the direction of transient condition performance research were discussed.

To investigate the effects of geometric parameters of Pelton turbine bucket on hydraulic performance and internal flow characteristics,the homogeneous multiphase flow model and SST k-ω turbulence model were selected to simulate the unsteady gas-liquid two-phase flow of the Pelton turbine. Orthogonal experimental studies were conducted on bucket width, depth, exit angle, and the inclination angle of splitter for different combinations. Through range analysis, it is found that the bucket width is the most critical factor affecting efficiency and output power, followed by the inclination angle of splitter, exit angle and depth. Analysis of the flow field under different bucket widths reveals that the efficiency of the Pelton turbine shows a gradually increasing trend as the bucket width increases. Compared with a bucket width of 100 mm, the relative efficiency of the Pelton turbine increases by 9.27% when the bucket width increases to 108 mm. At the moment of maximum torque, the high pressure area of the bucket rapidly increases as bucket width increases, which leads to an increase in the bucket torque enhancing its working capacity.

In order to optimize atomization technology and meet the requirements of atomization performance, various forces such as jet pressure, gas shear force, and electrostatic field force can be utilized. These forces, acting collectively on the liquid, can effectively break up liquid droplets and significantly reduce their particle size. The effect of cavitation collapse shock waves plays a significant part in atomization technology, as it effectively promote the efficiency of the atomization process. Through this mechanism, the energy consumption of atomization technology can be significantly reduced. In this process, the dynamic behavior of cavitation bubbles and droplets influence each other. Revealing the physical mechanism is one of the important fundamental research topics for improving the performance of cavitation atomization. Due to the different geometric shapes of droplet in the atomization field, cavitation bubble jets in four kinds of droplet(the ellipsoidal, hemispherical, cylindrical, and spherical droplets)and the morphology effect on droplet splashing behavior were reviewed. Based on the high-speed photographic results of cavitation atomization phenomenon and physical field analysis of the gas-liquid interface, the mechanism of the influence of droplet morphology on shock wave propagation, jet morphology evolution and pressure field distribution was elaborated. Finally, the theoretical basis for further improving cavitation atomization performance in the future was provided.

According to the structural characteristics of a plant protection UAV with a linear multi-rotor aerodynamic layout, the impact of incoming flow from different directions on the spatial distribution of downwash flow during UAV hovering was analyzed using CFD method. Based on this analysis, single-factor and multi-factor orthogonal experimental research methods were further employed to systematically investigate the effects of flight altitude, flight speed, and lateral wind speed on downwash flow distribution and its variation. The results demonstrate that lateral flow interference has the most significant influence on the spatial distribution of downwash flow for a linear plant protection UAV in hover mode. The flight altitude, flight speed, and lateral wind speed exhibit linear correlations with the spatial distribution characteristics of the downwash flow field. Among these factors, flight speed exerts a higher degree of influence compared to lateral wind speed and flight height in terms of longitudinal vector velocity value within the downwash flow field. The methods and conclusions provide a theoretical reference for the future studies concerning droplet movement influenced by downwash flow.

To address the issue of excessive cogging torque in permanent magnet synchronous motors(PMSMs), an analytical expression was derived using the energy method to analyze the influence of segmented skew parameters and pole-arc coefficients on cogging torque. Simulation results demonstrate that the segmented skew parameters and pole-arc coefficients calculated from these analytical expressions can effectively reduce the amplitude of cogging torque. To validate the optimization effect, a second-order response surface model was established to describe the relationship between the segmented skew parameters, pole-arc coefficients, and the optimization objective, and it was extended to an eighth-order fitting model. The results indicate that higher fitting orders result in larger coefficients of determination, leading to higher fitting accuracy. Particle swarm optimization(PSO)was employed to perform global optimization of the key parameters. The simulation results show that the cogging torque amplitude is reduced by 96.060% with the second-order regression model. After the eighth-order fitting model, the amplitude further decreases to 96.452%, resulting in more significant optimization with minimal impact on the back EMF. Experimental results confirm the effectiveness of the proposed optimization strategy, which significantly reduces cogging torque and maintains motor performance stability.

To minimize energy consumption during emergency water diversion to Taihu Lake, while ensuring the water inflow requirements of Lake Taihu are met, the optimized coordinated operation scheme of the gate-pump station was proposed based on upstream and downstream water level patterns. The developed daily optimization sehcme for the tidal reach gate-pump system incorporated water diversion channel distribution, evaporation, and seepage losses. The objective was to minimize the daily operational energy consumption at the hydraulic complex. An improved Whale Optimization Algorithm(IWOA)was employed to solve the model and perform numerical simulations. During the joint operation of gate-pump station, when the combined water demand for Lake Taihu and system loss was below the gates′ maximum daily diversion capacity of the control gate, only the regulation gate opened for water diversion, and the pump station did not operate. When gravity flow through gates could not meet the daily water diversion requirement, the pump station supplemented the operation. Specifically, when inland water levels remained below Yangtze River tidal levels, self-flow water division through the control gate was used. When inland levels exceeded tidal levels, the pump station was operated to pump water. Results indicate that the optimized joint operation scheme of the gate-pump system can save energy consumption per unit water diversion by approximately 4.55% and 11.88%, respectively. The design operation scheme(0°)and the maximum blade angle operation scheme(2°), respectively. The improvement of the whale optimization algorithm based on the characteristic of the gate-pump optimization schemes effectively enhances the convergence speed and stability of the algorithm. These findings confirm that tide-optimized coordination of gate-pump operations in tidal reaches can significantly reduce energy consumption and provide theoretical support for operational management.

In addition to traditional chemical and physical pipeline cleaning techniques, researchers both domestically and internationally have proposed a novel high-concentration ice slurry cleaning technology. To explore the progress and future development trends of this technology, an overview of the principles, advantages, and disadvantages of traditional pipeline cleaning methods was provided. Then, the characteristics of ice slurry and various measurement methods for different concentrations of ice slurry. Following that, a detailed review of the principles and advantages of high-concentration ice slurry pipeline cleaning technology, related experiments and simulations, as well as cleaning devices was presented. Specific case illustrated the application of this technology in municipal water supply pipeline cleaning. This technology utilized the fluid and solid characteristics of ice slurry to achieve efficient decontamination while avoiding issues related to chemical residues and pipeline damage, offering significant advantages such as high cleaning efficiency and environmental safety. Finally, based on the existing shortcomings in ice slurry concentration measurement methods, waste liquid detection, and cleaning technologies, the future research directions was proposed from three aspects: fundamental theory of ice slurry, key technology research for high-concentration ice slurry pipeline cleaning, and applications. Future research should focus on improving measurement accuracy, enhancing waste liquid treatment systems, and optimizing processes for complex pipeline networks to inject new momentum into the pipeline cleaning industry.

In order to optimize the size of TiO₂ electrode and improve the comprehensive performance of on-line detection of pH value of cultivation substrate, TiO₂ thin film was deposited on Indium Tin Oxide/Glass(ITO/Glass)substrate by magnetron sputtering.Prepared pH sensitive electrodes with different film thicknesses, and pH sensors were constructed with solid Ag/AgCl reference electrodes. Scanning Electron Microscope(SEM)was used to observe the development law of electrode film surface morphology and analyze the response characteristics. The response characteristics of the sensor were tested in standard pH buffer solution. The results show that the thicker TiO₂ sensitive film has a better porous structure, and excellent response stability, but the response sensitivity is poor. The TiO₂ sensitive electrode with a film thickness of 200 nm and a film size of 15 mm×15 mm is synthesized. It has a comprehensive pH response performance close to that of a glass electrode sensor. In the application test of pH value detection of cultivation substrate by using optimal sensor, the maximum absolute error of pH value detection is 0.52 unit. By summarizing the error law, the mass moisture content model is constructed. After mass moisture content compensation, the maximum absolute error of pH value detection is reduced to 0.12 unit, and the relative error is below 5%, which meets the perfor-mance requirements of online pH value detection of cultivation substrates.

To improve the comprehensive filtration performance and ensure the efficient operation of micro-irrigation systems, a micro-pressure filtration platform was established for filtration performance tests. Based on multi-objective balanced optimization approach, the combined effects of filter mesh structure and suspended impurities on filtration performance under micro-pressure conditions was explored. Evaluation criteria included head loss rate, filtration efficiency, and cake regeneration rate. Response surface methodology was employed to construct objective models for each index. A hybrid weighting method, integrating subjective and objective approaches, together with the TOPSIS-based Pareto frontier method, enabled comprehensive performance evaluation and structural optimization of filter meshes. The results reveal a strong correlation between the fractal dimension of the mesh and filtration system performance, indicating its potential as a variable for subsequent experiments. The eva-luation indicators are ranked in descending order as follows: cake regeneration rate, head loss rate, and filtration efficiency. The obtained objective function models demonstrate high reliability. Reference schemes for filter mesh selection under various impurity conditions in the suspension are established. Wedge-shaped meshes with lower fractal dimensions are recommended as the overall optimal choice, offering superior performance in terms of both cleaning effectiveness and hydraulic behavior. These findings provide a valuable decision-making reference for the selection and engineering application of micro-pressure mesh filters.