Figure 3.

Evolution of the domain. The original domain is plotted in (a). At $t=10$, the arrows, showing the vector field $\mathbf{u}$, are pointing inward, since V is decreasing in (b) whereas in (c), they are pointing outward since V is increasing, which means that the domain is growing at $t=400$. Part (d–f) show the size of the domain at time $t=10$, 200, and 400, respectively.