Really depends on the type of flow: The Lambda-2 criterion is, e.g., very good in identifying idealized vortices as illustrated by Jeong, J. and Hussain, F.: On the identification of a vortex. J. Fluid Mech. 285, 69–94 (1995)

The Q-criterion may be used for more turbulent flow configurations as, e.g., for flow above a forest: Dupont, S. and Brunet, Y.: Coherent structures in canopy edge flow: a large-eddy simulation study. J. Fluid Mech. 630, 93–127 (2009)

Best wishes,

Josef

Thank you very much. Because I use large eddy simulation and have tried both ways to observe the flow. But it shows different results. The Reynolds number is very huge, around 100000. It seems Q-criterion show better results.