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from dolfin import *
#Create mesh and define function space
mesh = UnitSquareMesh(32, 32)
marker = MeshFunction("size_t", mesh, mesh.topology().dim(), 0)
for c in cells(mesh):
marker[c] = c.midpoint().x() < 0.5
submesh1 = MeshView.create(marker, 1)
submesh2 = MeshView.create(marker, 0)
# Define Dirichlet boundary
def boundarySub1(x):
return x[0] < DOLFIN_EPS
def boundarySub2(x):
return x[0] > 1.0 - DOLFIN_EPS
W1 = FunctionSpace(submesh1, "Lagrange", 1)
W2 = FunctionSpace(submesh2, "Lagrange", 1)
# Define the mixed function space
V = MixedFunctionSpace( W1, W2 )
# Define boundary conditions
u0 = Constant(0.0)
# Subdomain 1
bc1 = DirichletBC(V.sub_space(0), u0, boundarySub1)
# Subdomain 2
bc2 = DirichletBC(V.sub_space(1), u0, boundarySub2)
# Define variational problem
# Use directly TrialFunction and TestFunction on the product space
(u1,u2) = TrialFunctions(V)
(v1,v2) = TestFunctions(V)
f = Expression("10*exp(-(pow(x[0] - 0.5, 2) + pow(x[1] - 0.5, 2)) / 0.02)", degree=2)
# Subdomain 1
a1 = inner(grad(u1), grad(v1))*dx
L1 = f*v1*dx
sol1 = Function(V.sub_space(0))
solve(a1 == L1, sol1, bc1)
# Subdomain 2
a2 = inner(grad(u2), grad(v2))*dx
L2 = f*v2*dx
sol2 = Function(V.sub_space(1))
solve(a2 == L2, sol2, bc2)
# Save solution in vtk format
out_sub1 = File("functionspace-product-subdomain1.pvd")
out_sub1 << sol1
out_sub2 = File("functionspace-product-subdomain2.pvd")
out_sub2 << sol2
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