I need to assign a time dependent BCs. I first defined a Constant and then at every time step assign time dependent value to this constant. Everything works fine if I’m doing this in a function. However, when I try to do this in a python class, the time dependent BCs doesn’t work any more. Here’s a code example to reproduce this:
import matplotlib.pyplot as plt
from dolfin import *
# Optimization options for the form compiler
parameters["form_compiler"]["cpp_optimize"] = True
parameters["form_compiler"]["representation"] = "uflacs"
r_global=Constant((0.1,0,0))
class Test(object):
def __init__(self, useglobal=False):
if (useglobal):
print("Use global r")
self.r=r_global
else:
self.r = Constant((0.1,0,0))
return None
def setup(self):
# Create mesh and define function space
mesh = UnitCubeMesh(24, 12, 12)
V = VectorFunctionSpace(mesh, "Lagrange", 1)
# Mark boundary subdomians
left = CompiledSubDomain("near(x[0], side) && on_boundary", side = 0.0)
right = CompiledSubDomain("near(x[0], side) && on_boundary", side = 1.0)
# Define Dirichlet boundary (x = 0 or x = 1)
c = Constant((0.0, 0.0, 0.0))
bcl = DirichletBC(V, c, left)
bcr = DirichletBC(V, r, right)
self.bcs = [bcl, bcr]
# Define functions
du = TrialFunction(V) # Incremental displacement
v = TestFunction(V) # Test function
u = Function(V) # Displacement from previous iteration
B = Constant((0.0, -0.5, 0.0)) # Body force per unit volume
T = Constant((0.1, 0.0, 0.0)) # Traction force on the boundary
self.u=u
self.v=v
# Kinematics
d = len(u)
I = Identity(d) # Identity tensor
F = I + grad(u) # Deformation gradient
C = F.T*F # Right Cauchy-Green tensor
# Invariants of deformation tensors
Ic = tr(C)
J = det(F)
# Elasticity parameters
E, nu = 10.0, 0.3
mu, lmbda = Constant(E/(2*(1 + nu))), Constant(E*nu/((1 + nu)*(1 - 2*nu)))
# Stored strain energy density (compressible neo-Hookean model)
psi = (mu/2)*(Ic - 3) - mu*ln(J) + (lmbda/2)*(ln(J))**2
# Total potential energy
Pi = psi*dx - dot(B, u)*dx - dot(T, u)*ds
# Compute first variation of Pi (directional derivative about u in the direction of v)
F = derivative(Pi, u, v)
# Compute Jacobian of F
J = derivative(F, u, du)
self.F=F
self.J=J
dt = 0.1
t=0
# file = File("displacement.pvd")
while t < 0.5:
t+=dt
self.r.assign(Constant((t,0,0)))
print(self.r.values())
# Solve variational problem
solve(self.F == 0, self.u, self.bcs, J=self.J)
return None
TT_useglobal=Test(useglobal=True)
TT_useglobal.setup()
The code runs fine but these lines appear to not have any effect on the simulation:
self.r.assign(Constant((t,0,0)))
Any suggestions?
