This study investigates the leakage vortex influence on pressure pulsation characteristics within a vertical axial flow pump. Three impeller configurations with blade root clearance (δ) of 2.7–8.0 mm were designed to analyze geometric effects on internal flow dynamics. Unsteady RANS simulations predicted flow structures under multiple operating conditions (0.8–1.2Q_des). Fast Fourier Transform (FFT) extracted frequency–domain and time–frequency characteristics of pressure pulsations in critical flow regions. Key results reveal: (1) δ enlargement expands low-pressure zones within blade channels due to enhanced leakage vortices; (2) leading-edge pulsation shows 8.2–11.7% reduction in peak-to-peak amplitude and fundamental frequency magnitude with increasing δ; (3) trailing-edge response exhibits non-monotonic behavior, with maximum amplitude at δ = 5.0 mm (42.2% increase at design flow). These findings demonstrate that blade root clearance optimization requires condition-dependent thresholds to balance leakage management and pulsation control.

Blade tip leakage vortex (TLV) is a critical phenomenon in hydraulic machinery, which can significantly affect the internal flow characteristics and deteriorate the hydraulic performance. In this paper, the blade tip leakage flow and TLV characteristics in a novel dishwasher pump were investigated. The correlation between the vorticity distribution in various directions and the leakage vortices was established within a rotating coordinate system. The results show that the TLV in a composite impeller can be categorized into initial and secondary leakage vortices. The initial leakage vortex originates from the evolution of two corner vortices that initially form at different locations within the blade tip clearance. This vortex induces pressure fluctuations at the impeller inlet; its shedding is identified as the primary contributor to localized energy loss within the flow passage. These findings provide insights into TLVs in complex pump geometries and provide solutions for future pump optimization strategies.

A novel gas–liquid nozzle is designed to address the limited energy efficiency of single-phase jet impingement systems. By leveraging the pressure drop generated in the nozzle converging section, the design facilitates gas injection to form a gas–liquid jet that enhances impingement performance. However, the geometric influence of the gas–liquid nozzle and the resulting water film characteristics upon impingement remain unclear. In this study, three-dimensional computational fluid dynamics (CFD) simulations were conducted on the circular water film (CWF) generated by a gas–liquid jet. The influence of key nozzle parameters on stagnation pressure was analyzed using the response surface method, revealing that the nozzle contraction radius is the dominant factor. High-speed imaging and jet impact force experiments were conducted to validate the performance of the optimized nozzle. The results show that the regression model, using stagnation pressure as the response variable, illustrates excellent predictive accuracy. Compared with the original design, the optimized nozzle consistently produced a larger water film area and a superior impingement performance due to the formation of internal air bubbles within the film. Moreover, the optimized nozzle demonstrated a consistently higher jet impact force coefficient than the original nozzle under all tested conditions. This work presents a novel gas–liquid nozzle design and a systematic optimization framework grounded in the analysis of circular water film characteristics.