A new Omega (Ω) method with ε determination is introduced to represent the
ratio of vorticity square over the sum of vorticity squared and deformation squared, for
vortex identification. the advantages of the new Ω method can be summarized as follows:
(1) Ω, as a ratio of the vorticity squared over the sum of the vorticity squared and
deformation squared, is a normalized and case-independent function which satisfies Ω
∈[0,1]; (2) Compared with the other vortex visualization methods, which require a wide
threshold to capture the vortex structures, Ω can always be set as 0.52 to capture vortex
for different cases and time steps; (3) ε is defined as a function without any adjustment
on its coefficient for all cases; (4) The Ω method can capture both strong and weak
vortices simultaneously. In addition, Ω is quite robust with no obvious change in vortex
visualization.
Keywords: Case-independent, Deformation, Omega method, Vortex identification,
Vorticity.