Solution
= Solution
$\omega(t)=\omega_0\exp(\int_0^t\alpha(s)ds)$. Positive $\alpha$ stretches material lines vertically; conservation of vortex flux through the shrinking transverse area amplifies <vorticity>.
= Solution
$\omega(t)=\omega_0\exp(\int_0^t\alpha(s)ds)$. Positive $\alpha$ stretches material lines vertically; conservation of vortex flux through the shrinking transverse area amplifies <vorticity>.