Hi all,
I am a bit confused regarding applying a pointsource in a mixedfunctionspace.
In the example below it seems the delta function is only seen in the real-valued part of the solution.
from dolfin import *
mesh = UnitSquareMesh(6,4)
ele = FiniteElement("CG", mesh.ufl_cell(), 1)
V = FunctionSpace(mesh, MixedElement([ele,ele]))
u, v = TrialFunction(V), TestFunction(V)
u_r, u_i = split(u)
v_r, v_i = split(v)
f_r = Constant(0.)
f_i = Constant(0.)
def u0_boundary(x, on_boundary):
return on_boundary
bc = DirichletBC(V, Constant((0,0)), u0_boundary)
a_r = inner(grad(u_r),grad(v_r)) * dx - inner(grad(u_i),grad(v_i)) * dx
a_i = inner(grad(u_r),grad(v_i)) * dx + inner(grad(u_i),grad(v_r)) * dx
L_r = inner(f_r,v_r) * dx - inner(f_i,v_i) * dx
L_i = inner(f_r, v_i) * dx + inner(f_i,v_r) * dx
a = a_r+a_i
L = L_r+L_i
A = assemble(a)
b = assemble(L)
bc.apply(A,b)
ps_r = PointSource(V.sub(0), Point(.5,.5))
ps_i = PointSource(V.sub(1), Point(.5,.5))
ps_r.apply(b)
ps_i.apply(b)
print b.array() # inspect ps has been applied
u = Function(V)
solve(A, u.vector(), b, 'lu')
u_r, u_i = u.split(True)
plot(u_i);plot(u_r);interactive()
If I for example apply something like a very small circle on a fine mesh instead of a pointsource both solutions are the same again:
f_q= Expression("sqrt((x[0] - x0)(x[0] - x0) + (x[1] - y0)(x[1] - y0)) < r ? q : 0.0", x0=.5, y0=.5, z0=.5, r=.01, q = 1, degree=2)
How come this does not work with PointSource?
Thanks in advance
