Hi, I would like to prescribe a boundary condition for an initial time duration and then remove it for the remaining time duration. Commercial finite element solvers allow you to do this by specifying steps. I tried to implement it using the code below. This is giving nonsensical results at and after the time at which the BCs change. Can you please assist me in how I may implement this properly. I can share the full code if needed. m = rho*inner((u - 2.0 * u_n + u_nm1),v) / Constant(dt * dt) * dxlump k= inner(sigma(u_n),epsilon(v))*dx def collar_load(t,T,freq,amp=1.0): return amp*hanning(t,T)*stepfn(t,T)*np.sin(freq*t) # Define the loading as an expression depending on t t=0 collar_disp= Constant([0.0, 0.0, 0.0]) F = m+k a, r = lhs(F), rhs(F) zero = Constant((0.0, 0.0, 0.0)) # Dirichlet BC that is valid for the entire time duration bc1 = DirichletBC(V, zero, 11) # Collar BC that remains on till T_pulse bc2= DirichletBC(V, collar_disp, 21) # My attempt of defining two problems to mimic two simulation steps problem1 = LinearVariationalProblem(a, r, u_np1, bcs=[bc1,bc2], constant_jacobian=True) solver1 = LinearVariationalSolver(problem1, solver_parameters=params) problem2 = LinearVariationalProblem(a, r, u_np1, bcs=[bc1], constant_jacobian=True) solver2 = LinearVariationalSolver(problem2, solver_parameters=params) for i in range(len(time)): t = time[i] if (t<=T_pulse): solver1.solve() else: solver2.solve() u_nm1.assign(u_n) u_n.assign(u_np1) -- Abhishek Venketeswaran NETL Research Associate - ORISE National Energy Technology Laboratory Department of Energy abhishek.venketeswaran@netl.doe.gov Work: 412-386-4833 Mobile: 716-507-7890 www.netl.doe.gov<http://www.netl.doe.gov> [cid:97ebd409-8c9c-4361-9753-e4c626433151]
