Visualization: Isosurfaces

Visualization of 3D flow fields is a dark art. Consider these two visualization of the same uEQ8, or "hairpin vortex" equilibrium solution:

fixed sections of the Eulerian velocity field u = (u,v,w)

isosurfaces, vortex lines
[laminar equilibrium] uUB mixing
Itano and Generalis visualization:
yellow curves: vortex lines.
isosurfaces of ux = 0.1 and 0.4, (cyan and blue, respectively) reveal low-speed structures within the flow.