Hello Katie
Is the equation that you are trying to solve time-dependant? For the look of your assembly function it appears that you're solving the stationary equation with different boundary conditions. In the run function you advance through time and solve the equation each time step although you're not using the previous solution to calculate the current one, and you're only saving the output for a few time steps, wouldn't be same just to calculate those time steps without compute the intermediate ones? Regards Javier 2012/6/22 Katie Leonard <[email protected]> > Hello, > > I am having trouble applying time-dependent boundary conditions properly. > I attach two minimal working examples, and a picture to show what I mean. > > In these examples I am solving Laplace equation on a circle, with zero > flux boundary conditions, and time dependent Dirichlet boundary conditions, > so that > > \nabla^2 p = 0 in \Omega > > with > \nabla p \cdot \mathbf{n} = 0 on \partial \Omega > p = f(t) on \partial \Omega > > > In the first example (no_constraints_t_dependent_boundary.cc) I implement > the boundary conditions using VectorTools::interpolate_boundary_values > and MatrixTools::apply_boundary_values each time assemble_pressure_system > () is called. > In the second example (with_constraints_matrix_t_dependentBCs.cc) I use a > constraints matrix, and call VectorTools::interpolate_boundary_values > within setup_pressure_dofs_for_boundary (), calling this at the beginning > of each timestep. > > Both codes produce the same results - but giving the wrong answer (see > Example_pressure_plot.jpeg) > > If anyone has any ideas why this is occurring, and how to solve it, I > would be very grateful! > > > Many thanks and have a good weekend! > > Katie > > > > Katie Leonard > > DPhil student in Computational Biology, > The University of Oxford. > _______________________________________________ > dealii mailing list http://poisson.dealii.org/mailman/listinfo/dealii > > -- José Javier Muñoz Criollo PhD Student | Cardiff University School of Engineering E-mail: [email protected]
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