LAUSR

A new vortex identification method (Liu et al. 2016) was proposed to represent the rotation relative strength and capture and visualize the vortices in our previous study. The basic idea of the Ω method is that a ratio of the vorticity squared over the summation of the vorticity squared and the deformation squared should be used to measure the relative rotation strength. However, the vorticity tensor norm is not objective. Thus, a moving observer will observe different vortex structures in a moving reference frame, which will make people confused with the real vortex structures. In the present study, by the definitions of the net spin tensor and net vorticity vector, an objective omega vortex identification method is presented and the examples are presented to verify the vortex structures will still retain in a moving reference frame.