Ventilated cavitation involves complex multiphase flow, phase change, and turbulence, posing challenges for accurate prediction and control. This paper investigates the performance of three turbulence models—Large Eddy Simulation (LES), Detached Eddy Simulation (DES), and Shear Stress Transport (SST)—in predicting the unsteady characteristics and entropy generation mechanisms in ventilated cavitation around a hydrofoil. A comparative analysis with experiments reveals each model's strengths and limitations in capturing cavitation and turbulence at various scales. The results demonstrate that the LES model excels in resolving small-scale turbulent structures, cavitation formation and shedding, as well as reverse flow and vortex dynamics, making it highly suitable for detailed analysis of complex cavitation phenomena. The DES model shows robustness in predicting large-scale flow features but exhibits delays when handling bubble motion near the hydrofoil's trailing edge. The SST model achieves a balance between computational accuracy and efficiency in predicting flow separation and vortex structures, making it ideal for trend analysis in engineering applications. By analyzing boundary vorticity flux lines, Q-criterion, and Omega methods, the study confirms the LES model's superior capability in capturing intricate vortex structures in high-turbulence regions, while also revealing the dynamic evolution of entropy generation during cavitation. Overall, the LES model proves to be the most effective for precise simulation of ventilated cavitation phenomena, while the DES and SST models are better suited for large-scale flow analysis and practical engineering applications, respectively. This research provides theoretical and technical support for the prediction and control of complex ventilated cavitation flows.

Multistage pumps are essential in emergency water supply, irrigation, and other systems undergoing unavoidable hydraulic transitions like pump startup and valve operations. These transitions cause rapid changes in impeller speed, flow rate, and pressure, destabilizing the internal flow field and impacting system reliability. To study transient flow characteristics, a numerical analysis of a three-stage pump was conducted, focusing on vortex identification, entropy production, and time–frequency pressure pulsation. Using the SST turbulence model, the simulation analyzed different start times and flow rate variations. Findings revealed that shorter startup times intensified transient effects, with the head increasing rapidly initially and then stabilizing. Vortex structures showed periodic development and dissipation. Entropy production rose with impeller speed, peaking higher with shorter startups. Blade passing frequency dominated pressure pulsations, with increased low-frequency pulsations as speed rose. During valve opening, flow stabilization accelerated with increasing flow rates, reducing amplitude and eliminating low-frequency components. This research aids the reliable operation of high-pressure pumping systems in energy storage.

A numerical method using combined detached-eddy simulation (DES) and a cavitation model considering the rotation effect is used for unsteady cavitation flow field of the centrifugal pump. A closed-type pump test system was established to obtain the pump performance and pressure pulsation characteristics under different flow rates and cavitation condition, which provide boundary conditions and verification of calculations. Based on the calculation results of the unsteady flow field of the centrifugal pump cavitation, the entropy generation analysis of the flow field and an analysis of the pressure fluctuation characteristics were carried out. Then, we tried to reveal the relationship between cavitation and the deterioration of the centrifugal pump performance and the generation of the unstable operation excitation force. The internal energy loss is mainly concentrated in the impeller, volute, and pump cavity area, which accounts for more than 85% of the total entropy generation. The characteristic frequency of a Strouhal number of about 0.333 appears at the volute tongue due to the cavitation flow spread downstream.

Most of the research on the cavitation with entrained air has focused on the military direction, but it ,about centrifugal pumps, which is relevant to people's livelihood, is still relatively lacking. In order to study the basic law of the development of cavitation inside centrifugal pumps under aeration conditions, a test bench suitable for cavitation experiments with incoming flow containing gas was obtained. Furthermore, a single-stage single-suction 6-blade centrifugal pump was used as the research object to conduct pressure pulsation experiments under cavitation condition when the incoming flow was 1.0% air viod fraction at 2900r/min-50m3/h. The results showed that: After cavitation happened, the greater aeration content will deteriorate the pump's anti-cavitation performance, but the head curve is more gentle in falling down compared to natural cavitation. Hence aeration has a beneficial effect on the performance degradation of the pump under the cavitation condition. At the same time, before the cavitation number drops to the fracture cavitation number of the pump, aeration has improvement in the efficiency of the pump in different degrees , especially in the situation with the ventilated rate of 1.0%. The main frequency of pressure pulsation at the inlet and outlet of the test pump after aeration is dominated by the blade frequency. The shaft frequency signal at the outlet gradually decreases with the cavitation number lessened. Moreover the amplitude of the blade frequency grows slightly with the reduction of the cavitation number. But it tends to soar when the cavitation number is less than the fracture cavitation number.

The high-power consumption and excessive heat generation in data centers present challenges to thermal management. As a critical component of liquid cooling systems, the circulation pump's stability and reliability are directly impacted by cavitation and air entrainment, which degrade performance. This study investigates the effects of cavitation with entrained air under various rotational speeds and air volume fractions on centrifugal pump performance, pressure pulsation, and cavitation behavior. Experiments were conducted using a closed-loop test rig at three rotational speeds (2900, 2300, and 1800 r/min). The impact of different air volume fractions on the time-domain and frequency-domain characteristics of pressure pulsations was systematically analyzed. The results reveal that: (1) The maximum efficiency under air entrainment conditions exceeds that under natural cavitation. This condition optimizes the pressure distribution within the impeller channels, particularly near the impeller outlet. (2) Air entrainment effectively suppresses high-amplitude pressure fluctuations caused by cavitation collapse, especially at high air volume fraction (1.6%), with varying effects observed during the cavitation stage depending on the air volume fractions. (3) The ratio of rotational speed to bubble volume fraction determines the frequency-domain characteristics, manifesting as a combination of blade frequency, broadband, and low-frequency signals, influencing flow field stability and energy distribution. (4) Cavitation and air–cavitation interference frequencies cluster around St = 6, indicating bubble aggregation, collapse, and fragmentation under impeller rotation, with distinct interaction patterns at different speeds. This study provides a novel theoretical explanation of the mechanisms by which bubble aggregation and fragmentation induce flow instability under low-speed conditions.