// convects1: theta-method border C(t=0, 2*pi) { x=cos(t); y=sin(t); }; mesh Th = buildmesh(C(100)); fespace Uh(Th,P1); Uh uold, u = exp(-10*((x-0.3)^2 +(y-0.3)^2)),v; real T = 2*pi, t = 0; int ts = 125; real dt = T/ts; Uh b1 = y, b2 = -x; real theta = 0; plot(u,wait=true); for (int n=0; n