Hi All,
Please can someone help with this. When I run the NonlinearVariationalProblem I get the following error. I cant seem to figure out what the problem is. Below is my code and the error.
Thanks for any help
from dolfin import *
#Subdomain for Perodic Boundary conditions
class PeriodicBoundary(SubDomain):
# left boundary is "target domain"
def inside(self, x, on_boundary):
return bool(x[0]< DOLFIN_EPS and x[0]> - DOLFIN_EPS and on_boundary)
# Map right boundary to left boundary
def map(self, x, y):
y[0] = x[0] - 1.0
y[1] = x[1]
pbc = PeriodicBoundary()
mesh = RectangleMesh(Point(-1,-1),Point(1,1),200,200) #Domain[-1,1]*[-1,1]
V1= VectorFunctionSpace(mesh, 'CG', degree=2, constrained_domain = pbc)
V2=VectorFunctionSpace(mesh, 'CG', degree=2, constrained_domain= pbc)
Q1 = FunctionSpace(mesh, 'CG', degree=1, constrained_domain = pbc )
Q2 = FunctionSpace(mesh, 'CG', degree=1, constrained_domain = pbc)
VQ = MixedFunctionSpace([V1,V2, Q1, Q2])
# Define trial and test functions
duu = TrialFunctions(VQ)
m,h,q,r = TestFunctions(VQ)
H= Function(VQ)
U,u, phi,p = split(H)
# Dirichlet boundary condition
# Sub domain for Dirichlet boundary condition
class Top(SubDomain):
def inside(self, x, on_boundary):
return (x[1]>1 - DOLFIN_EPS and on_boundary)
class Bottom(SubDomain):
def inside(self, x, on_boundary):
return (x[1]< -1 + DOLFIN_EPS and on_boundary)
UB= Constant((-1,0))
UT= Constant((1,0))
ub= Constant((-1,0))
ut= Constant((1,0))
top= Top()
bott = Bottom()
bcUB= DirichletBC(VQ.sub(0), UB ,bott)
bcUT= DirichletBC(VQ.sub(0), UB ,top)
bcub= DirichletBC(VQ.sub(1), ub ,bott )
bcut= DirichletBC(VQ.sub(1), ub ,top )
bcs = [bcUB,bcUT, bcub,bcut]
#constants
c = Constant (2/3)
xi0= Constant(1)
n = Constant(2)
alpha = Constant(25)
# initial conditions
U_int = Expression(["x[1]", "x[1]"])
u_int = Expression(["x[1]", "x[1]"])
phi_int= Constant(0.01)
p_int = Constant(0.0)
U00 = interpolate(U_int, V1)
u00= interpolate(u_int,V2)
phi00=interpolate(phi_int,Q1)
p00 = interpolate(p_int, Q2)
U0 = U00
u0 = u00
phi0 = phi00
p0 = p00
k_phi = (phi/phi0)**n
eta = exp(-alpha*(phi-phi0))
xi = xi0* eta
dt=0.01
f1 = phi*q*dx - phi0*q*dx - dt*div((1-phi)*U)*q*dx
f2 = inner(phi*(u-U), m)*dx + k_phi * p*div(m)*dx
f3 = p*div(h)*dx + eta*inner(grad(U) + grad(U).T, grad(h))*dx - (xi*div(U)) *div(h)*dx + c*(eta*div(U))*div(h)*dx
f4 = div(phi*u + (1-phi)*U)*r*dx
F1 = f1 + f2 + f3 + f4
T_total = 1
t=dt
while (t<=T_total):
F = action(F1, H)
Jac = derivative(F, H)
problem = NonlinearVariationalProblem(F,H,bcs, Jac)
solver = NonlinearVariationalSolver(problem)
solver.solve()
t+=dt
(U00, u00, phi00, p00).assign(H)
problem = NonlinearVariationalProblem(F,H,bcs, Jac)
File "/usr/lib/python2.7/dist-packages/dolfin/fem/solving.py", line 153, in init
cpp.NonlinearVariationalProblem.init(self, F, u, bcs, J)
File "/usr/lib/python2.7/dist-packages/dolfin/cpp/fem.py", line 2627, in init
_fem.NonlinearVariationalProblem_swiginit(self,_fem.new_NonlinearVariationalProblem(*args))
RuntimeError:
*** -------------------------------------------------------------------------
*** DOLFIN encountered an error. If you are not able to resolve this issue
*** using the information listed below, you can ask for help at
*** fenics@fenicsproject.org
*** Remember to include the error message listed below and, if possible,
*** include a minimal running example to reproduce the error.
*** -------------------------------------------------------------------------
*** Error: Unable to define nonlinear variational problem F(u; v) = 0 for all v.
*** Reason: Expecting the residual F to be a linear form (not rank 0).
*** Where: This error was encountered inside NonlinearVariationalProblem.cpp.
*** Process: 0
*** DOLFIN version: 1.6.0
*** Git changeset: unknown
*** -------------------------------------------------------------------------
