# Define boundary condition on left and right boundary
u0 = Constant(0.0)
bc = DirichletBC(V, u0, boundary)
# Define variational problem, simply copied from FEniCS demo
u = TrialFunction(V)
v = TestFunction(V)
f = Expression("10*exp(-(pow(x[0] - 0.5, 2) + pow(x[1] - 0.5, 2)) / 0.02)",
degree=2)
g = Expression("sin(5*x[0])", degree=2)
a = inner(grad(u), grad(v)) * dx
L = f * v * dx + g * v * ds
while precice.is_coupling_ongoing(
): # potential time loop, currently only one timestep is done
# Compute solution
u = Function(V)
solve(a == L, u, bc)
# Save solution in VTK format
file = File("poisson.pvd")
file << u
# write data to preCICE and advance coupling
precice.write_data(u)
precice.advance(precice_dt)
precice.finalize()
precice.store_checkpoint(u_n, t, n)
read_data = precice.read_data()
# Update the coupling expression with the new read data
precice.update_coupling_expression(coupling_expression, read_data)
dt.assign(np.min([fenics_dt, precice_dt]))
# Compute solution
solve(a == L, u_np1, bcs)
# Dirichlet problem obtains flux from solution and sends flux on boundary to Neumann problem
determine_heat_flux(V_g, u_np1, k, fluxes)
fluxes_y = fluxes.sub(1) # only exchange y component of flux.
precice.write_data(fluxes_y)
precice_dt = precice.advance(dt(0))
if precice.is_action_required(precice.action_read_iteration_checkpoint()
): # roll back to checkpoint
u_cp, t_cp, n_cp = precice.retrieve_checkpoint()
u_n.assign(u_cp)
t = t_cp
n = n_cp
else: # update solution
u_n.assign(u_np1)
t += float(dt)
n += 1
if precice.is_time_window_complete():
# See https://github.com/precice/fenics-adapter/issues/113 for details.
read_data[(0, 0)] = u_D(0, 0)
# Update the coupling expression with the new read data
precice.update_coupling_expression(coupling_expression, read_data)
dt.assign(np.min([fenics_dt, precice_dt]))
# Compute solution u^n+1, use bcs u_D^n+1, u^n and coupling bcs
solve(a == L, u_np1, bcs)
# Write data to preCICE according to which problem is being solved
if problem is ProblemType.DIRICHLET:
# Dirichlet problem reads temperature and writes flux on boundary to Neumann problem
determine_gradient(V_g, u_np1, flux)
precice.write_data(flux)
elif problem is ProblemType.NEUMANN:
# Neumann problem reads flux and writes temperature on boundary to Dirichlet problem
precice.write_data(u_np1)
precice_dt = precice.advance(dt(0))
if precice.is_action_required(precice.action_read_iteration_checkpoint()): # roll back to checkpoint
u_cp, t_cp, n_cp = precice.retrieve_checkpoint()
u_n.assign(u_cp)
t = t_cp
n = n_cp
else: # update solution
u_n.assign(u_np1)
t += float(dt)
n += 1
for ps in forces_x:
ps.apply(b_forces)
for ps in forces_y:
ps.apply(b_forces)
for ps in forces_z:
ps.apply(b_forces)
assert (b is not b_forces)
solve(A, u_np1.vector(), b_forces)
dt = Constant(np.min([precice_dt, fenics_dt]))
# Write relative displacements to preCICE
u_delta.vector()[:] = u_np1.vector()[:] - u_n.vector()[:]
precice.write_data(u_delta)
# Call to advance coupling, also returns the optimum time step value
precice_dt = precice.advance(dt(0))
# Either revert to old step if timestep has not converged or move to next timestep
if precice.is_action_required(precice.action_read_iteration_checkpoint()
): # roll back to checkpoint
u_cp, t_cp, n_cp = precice.retrieve_checkpoint()
u_n.assign(u_cp)
t = t_cp
n = n_cp
else:
u_n.assign(u_np1)
t += float(dt)
n += 1