Figure 6.

Contour plot of the instantaneous vorticity field for case $h_0=c,\psi ={90}^{\circ }$ and $St=0.1935$. (a) ${\theta }_0=1^{\circ }$; (b) ${\theta }_0=5^{\circ }$; (c) ${\theta }_0={10}^{\circ }$; (d) ${\theta }_0={15}^{\circ }$; (e) ${\theta }_0={20}^{\circ }$; (f) ${\theta }_0={25}^{\circ }$.