Unmanned Aerial Vehicle (UAV) path planning has increasingly become the key research point for civilian drones to expand their use and enhance their work efficiency. Focusing on offline derivative algorithms, represented by Rapidly-exploring Random Trees (RRT), are widely utilized due to their high computational efficiency. However, deploying these offline algorithms in complex and changing disaster environments presents its own drawbacks, such as slow convergence speed, poor real-time performance, and uneven generation paths. In this paper, the Artificial Potential Field -Improved Rapidly-exploring Random Trees (APF-IRRT*) path-planning algorithm is proposed, which is applicable to disaster relief UAV cruises. The RRT* algorithm is adapted with adaptive step size and adaptive search range coupled with the APF algorithm for final path-cutting optimization. This algorithm guarantees computational efficiency while giving the target directivity of the extended nodes. Furthermore, this algorithm achieves remarkable progress in solving problems of slow convergence speed and unsmooth path in the UAV path planning and achieves good performance in both offline static and online dynamic environment path planning.

The pump-turbine is the core component of a pumped storage power station. This paper considers an in-depth analysis of the rotor-stator interaction characteristics under computational fluid dynamics (CFD) and experimental measurements of pump-turbine with splitter blades used in a domestic pumped storage power station. The results show that as the guide blade opening increases, the rotor-stator interaction of the pump-turbine intensifies and the magnitude of the runner radial force and its pulsation amplitude as well as the magnitude of the guide blade water moment and its pulsation amplitude also increase. In addition, when the opening degree increases from 9.8° to 17.5°, the influence on the main frequency is mainly reflected in the phase change. While the opening degree increases from 17.5° to 24.8°, the influence on the main frequency is mainly reflected in the amplitude change. Moreover, the amplitude of 5f_n at opening 9.8° and opening 24.8° is greater than the optimal opening 17.5°, indicating that deviation from the optimal opening will aggravate the difference of rotor-stator interaction between splitter blades and guide blades. In the paper, the influence of guide blade openings on the rotor-stator interaction between the splitter guide blade is studied, which provides a theoretical reference for the stable operation of the pump-turbine.

Ice slurry is a phase-changing material composed of liquid water, ice crystals, and a freezing point depressant. It is finer and more uniform compared to ice cubes or flake ices and is used in many industries, such as food preservation, comfortable cooling, medical protective cooling, sport cooling, instrument cooling, firefighting, and artificial snowmaking, due to its high energy storage density. Ice slurry with high concentration can be used for cleaning equipment as its friction is several times greater than that of water at the same flow rate. This paper describes in detail the developments of ice slurry, including production methods, concentration measurement approaches, flow and heat transfer characteristics, as well as its applications in various industries. Problems to be solved or improved are also discussed, providing suggestions for better developments and applications in industrial environments.

The flow in the vertical long-axis fire pump exhibits complex, three-dimensional, unsteady flow features. In an attempt to understand the effects of turbulence models on the flow mechanism and performance characteristics of the pump, the ANSYS CFX software was used to carry out numerical studies on the vertical fire pump using URANS. The main objective of this study was to investigate the unsteady flow dynamics within the vertical fire pump and the influence of applying different computational turbulence models. The study then sought to conduct a brief analysis of the unsteady pressure pulsation characteristics of the pump. The reliability of the CFD model was validated with an external characteristic test. The transient pressure distribution, velocity field and external characteristics were analyzed. The results were compared to experimental results, where it was revealed that the SST k-ω model showed 1.82% and 0.81% improvements in efficiency and head, respectively, over the k-ε models. In terms of the power performance, however, the standard k-ε is less likely to over-predict the power used by the pump in overload conditions as compared to the other turbulence models. The pressure charts did not show significant reactions to varying turbulence models across all the studied flow rates. However, the velocity streamlines revealed that there were several disruptions in streamwise flow, where both the standard and RNG k-ε models exhibited more recirculation areas than the SST k-ω and standard k-ω models. Overall, for this type of application, SST k-ω was the best-performing turbulence model, while RNG k-ε showed the poorest performance. Nonetheless, the RNG k-ε also has its strengths. This investigation would serve as a theoretical reference for further research and development in fluid machinery.

Centrifugal pumps are widely used and are known to be sensitive to inlet air-water two-phase flow conditions. The pump performance degradation mainly depends on the changes in the two-phase flow behavior inside the pump. In the present paper, experimental overall pump performance tests were performed for two different rotational speeds and several inlet air void fractions (α_i) up to pump shut-off condition. Visualizations were also performed on the flow patterns of a whole impeller passage and the volute tongue area to physically understand pump performance degradation. The results showed that liquid flow modification does not follow head modification as described by affinity laws, which are only valid for homogeneous bubbly flow regimes. Three-dimensional effects were more pronounced when inlet void fraction increased up to 3%. Bubbly flow with low mean velocities were observed close to the volute tongue for all α_i, and returned back to the impeller blade passages. The starting point of pump break down was related to a strong inward reverse flow that occurred in the vicinity of the shroud gap between the impeller and volute tongue area.

This paper takes a pump-turbine as the research subject and, based on the Computational Fluid Dynamics (CFD) numerical method and combined with test data, investigates the pressure fluctuation characteristics in the pump mode and analyzes the pressure fluctuation characteristics at 0.75 Q_d, 1.0 Q_d and 1.25 Q_d when the guide vane opening is 17.5°. The results showed that the protruding frequencies of pressure fluctuation in the bladeless region were mainly 5 f_n, 10 f_n and 20 f_n, and the main frequencies in the runner area and near the outlet wall of the draft tube were 16 f_n and 5 f_n, respectively. At different heights for the guide vanes, the pressure fluctuation in the bladeless region had significant differences, and the pressure fluctuation near the bottom ring was the most intense. The amplitude of the rotor–stator interaction frequency continuously attenuates from the bladeless region to the outlet of the stay vanes, and the amplitude attenuation of each frequency is mainly concentrated in the area of the guide vanes. In this paper, the influence of different flow rates on the pressure fluctuation in the pump mode is analyzed, which provides a theoretical reference for the stability and further study of pump-turbines.