Numerical investigation of how gap size influences tip leakage vortex cavitation inception using a Eulerian-Lagrangian method

This paper investigates the effect of gap size on the inception of tip leakage vortex cavitation (TLVC) with a hybrid Eulerian-Lagrangian model. Good agreement is achieved between the simulation results and experimental data for velocity distributions around the TLV, bubble motion, and its size oscillations. It is found that the minimum pressure criterion is not accurate enough for the prediction of TLVC inception due to the significant effect of pressure fluctuation and increased concentration of nuclei in the TLV core region. The pressure fluctuation in the TLV core is noted to be a non-negligible factor, while the corresponding effect on nuclei dynamics in the TLV core is still unclear. To deal with this problem, the inducement of this excited turbulence is further analyzed and discussed in detail, which shows a close relationship with the TLV instability raised by the vortical interaction between TLV and tip-separation vortex/induced vortex. Our work provides an insight into the mechanism of TLVC inception through the flow characteristics in the TLV core region, which is helpful for controlling TLVC inception in engineering designs.