Comparative Study of different vortex identification methods in a tip-leakage cavitating flow

Abstract

The tip leakage vortex cavitating flow generated by a straight hydrofoil is computed using Large Eddy Simulation combined with Zwart-Gerber-Belamri cavitation model. Comparisons between the numerical and experimental results show a good agreement in velocity field and complicated vortical structures, including tip leakage vortex, tip separation vortex, the induced secondary vortices and wake vortices shedding off the foil. Spatial evolution of tip vortices is studied with three generations of vortex identification methods, including vorticity, Q-criterion (Hunt et al., 1988), the Ω method (Liu et al., 2016) and the Liutex method (Liu et al., 2018a). Performances of different methods are compared and explained, which indicate the advantages of Liutex method in the investigation of this flow regime. The evolution of tip vortices is observed to be affected by the free shear layer around TLV dramatically, which means that it may play an important role in TLV cavitating flow.