Figure 2.

Contour lines of the vorticity ω = v_x − u_y at t = 1.2 with initial (u^ρ, v^δ), δ = 0.05 using a 256 × 256 grid. (a) A thick shear layer with ρ = 30 and ν = 0. The contour levels range from −36 to 36 (cf. figure 3c in ref. 13). (b) A thin shear layer with ρ = 100 and ν = 5⋅10⁻⁵. The contour levels range from −70 to 70 (cf. figure 9b in ref. 13).