Abstract
To understand the effect of cavitation on the tip leakage vortex (TLV), turbulent cavitating flows were numerically investigated using the shear-stress transport (SST) k–ω turbulence model and the Zwart–Gerber–Belamri cavitation model. In this work, two computations were performed—one without cavitation and the other with cavitation—by changing the inlet pressure of the pump. The results showed that cavitation had little effect on the pressure difference between the blade surfaces for a certain cavitation number. Instead, it changed the clearance flow and TLV vortex structure. Cavitation caused the TLV core trajectory to be farther from the suction surface and closer to the endwall upstream of the blade. Cavitation also changed the vortex strength distribution, making the vortex more dispersed. The vortex flow velocity and turbulent kinetic energy were lower, and the pressure pulsation was more intense in the cavitating case. The vorticity transport equation was used to further analyze the influence of cavitation on the evolution of vortices. Cavitation could change the vortex stretching term and delay the vortex bending term. In addition, the vortex dilation term was drastically changed at the vapor–liquid interface.
Highlights
The tip clearance flow and vortex that develop in the clearance between the tip and the endwall of axial turbomachines occur in many hydraulic machines
You et al [14,15] studied the tip clearance flow using the large eddy simulation method. They focused on studying the instability of the tip leakage vortex structure and the potential mechanism of the low-pressure fluctuations caused by the cavities near the tip clearance
The pressure difference between the pressure surface and the suction surface of the blade was the cause of the clearance leakage flow and the tip leakage vortex (TLV)
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. You et al [14,15] studied the tip clearance flow using the large eddy simulation method They focused on studying the instability of the tip leakage vortex structure and the potential mechanism of the low-pressure fluctuations caused by the cavities near the tip clearance. They suggested that the velocity gradient generated by the gap jet was the cause of the production of vorticity and turbulent kinetic energy. The effect of cavitation on the TLV was discussed by the vorticity transport equation
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