Same as Fig. 10 but for cases where contraction acts on the field lines. The simulations presented here are the runs D10–D14 of Table 1 performed at Re_c = 5 × 10⁻¹ (green), Re_c = 1 (blue), and Re_c = 2 (purple). For all these cases L_u = 10⁴, but for Re_c = 5 × 10⁻¹ and 1, additional simulations are shown at L_u = 5 × 10³ in dash-dot lines. The analytical solution Eq. (40) is displayed in black dashed lines.