Plotting a given velocity field (vortex flow)

Hello every one !! I am simulating water flow on the stepped spillway.At each step there is a vortex flow.I have data of Vx( velocity in horizontal),Vz( velocity in upward) And Vortx( vorticity along x) And Vortz(Vorticity along upward direction,and q-criterion for vortex structures at every x and z ordinate.How can I quantify the vortex flow.I want to make a contour plot at each step showing vorticity.It should look like shown in the picture.

[Ashfaq Ahmed]

What do you mean by quantifying?