In this paper, to study the effect of dynamic and static interference of clearance flow in fluid machinery caused by changes in rotational speed, the model was simplified to a rotor-stator system cavity flow. Investigating the flow characteristics in the cavity by changing the rotor speed of the rotor-stator system is of considerable significance. ANSYS-CFX was applied to numerically simulate the test model and the results were compared with the experimental results of the windage torque of the rotor-stator system. The inlet flow rate and geometric model remained unchanged. With an increase in the rotating Reynolds number, the shear stress on the rotor wall gradually increased, and the maximum gradient was within l^* < 0.15. In addition to the shear stress, the tangential Reynolds stress R_rθ contributed partly to the torque on the rotor wall. The swirling vortex formed by entrainment in the cavity of the rotor-stator system tended to separate at Re_Φ= 3.53 × 10⁶. As the rotating Reynolds number continued to increase, the secondary vortex finally separated completely. The strength of the vortex in the rotor turbulent boundary layer decreased with an increase in the rotating speed, but the number of vortex cores increased with the increase of speed. Depending on the application of the fluid machine, controlling the rotating speed within a reasonable range can effectively improve the characteristics of the clearance flow.

To investigate the plasma shielding of laser-induced cavitation bubbles near a wall, a pulsed laser with different energies was selected to induce cavitation bubbles on the surface of 7050-T7451 aluminum alloy. A high-speed camera captured the evolution of the cavitation bubble, while a fiber-optic hydrophone system collected the acoustic signals during the evolution. Finally, a confocal microscope was used to view and analyze the surface morphology of 7050 aluminum alloy. The experimental results indicate that as the laser energy increases, the diameter, the evolution time, the pressure of the bubble, and both the pit diameter and depth all increase. Beyond an energy level of 1.4 J, the maximum diameter and the evolution time of the laser-induced cavitation bubble begin to decrease; the maximum diameter decreases by 2.04%, and the first evolution time decreases by 3.26%. Plasma shielding was observed in this experiment. Considering that the essence of a laser-induced cavitation bubble is the interaction between a high-energy laser and a liquid medium, the abnormal decrease in the maximum diameter, evolution time, and sound pressure epitomizes the manifestation of plasma shielding.

Investigating the flow characteristics in the cavity by changing the rotor profile of the rotor-stator system is of considerable significance, this paper simplifies clearance flow to rotor-stator cavity flow. The numerical simulation results are compared with the experimental results of the windage torque of the rotor-stator system, and the results show that the accuracy of the numerical calculation meets the requirements. The inlet flow rate and outlet gap were unchanged, and the flow in the concave cavity was most similar to the original model. The torque increased slightly and was more entrained, while the flow pattern of the convex cavity was more chaotic, and various forms of vortices appeared in the rotor boundary layer. The interference of the rotor and stator disks and the viscous effect of the fluid in the cavity are the main reasons for the generation of torque, and the Reynolds stress near the rotor wall also contributes partly to the torque. After data processing, an interesting phenomenon was observed. In the boundary layer of the rotor, the radial flow in which the inertial force plays a major role is transformed into a circular motion dominated by the rotation of the rotor.

The flow characteristics of multistage centrifugal pumps in transporting gas–liquid mixed media are highly complex; particularly, the unstable flow of the passage at high gas contents exacerbates energy losses, leading to a decrease in pump efficiency and stability. The excess energy loss in the pump is not conducive to the concept of sustainable development. In this study, a numerical simulation of multistage centrifugal pumps was conducted based on the Euler–Euler heterogeneous two-fluid model. This research revealed that gas primarily accumulates on the suction side of each impeller stage, and the gas distribution decreases progressively with each stage. As the interstage gas volume fraction (IGVF) increases, the gas accumulation within the pump becomes more pronounced. The gas volume fraction of each component is negatively correlated with the flow rate, and the change is more obvious in the impeller. The turbulent kinetic energy distribution inside the impeller is positively correlated with the gas distribution. There is a large fluctuation at 0.6Q and 0.8Q, and the distribution of the impeller vortex is asymmetric. However, the impeller has a lower turbulent kinetic energy near 1.2Q, which indicates that the emergence of gas in the medium increases the high-efficiency area of the multistage pump to a certain extent. This paper reveals how the gas phase is distributed, how energy is lost in the multistage pump, and the gas–liquid two-phase flow characteristics in the pump, which have certain guiding significance for the design and working-condition adjustments of the gas–liquid mixed pump.

This study investigated the flow characteristics of fluids within the narrow annular gap of a canned motor rotor, specifically focused on a 15-mm-wide rotor gap. By varying the inlet fluid flow rates and gas injection volumes, the formation of Taylor vortices and gas blockage phenomena under operational conditions are examined. Experimental observations confirm the emergence of Taylor–Couette flow within the annular region. Gas bubbles are entrained by the vortex structures, forming continuous helical gas bands that migrate toward the outlet. Due to buoyancy effects, phenomena such as bubble migration, gas band splitting, and recombination are observed, depending on the flow direction of the fluids. Under critical conditions, gas accumulation in the upper region of the gap leads to the onset of gas blockage, which may significantly affect flow stability and cooling performance. These results will offer a theoretical and experimental basis that serves as a foundation for optimizing the operational efficiency of canned motors.