Step 26 with advection term

[Sai P]

Hi,

I am a new dealii user and trying to extend step 26 with an advection term. If the method is implicit, I am not sure how to handle the boundary terms due to upwinding boundary in the advection term. It looks like the following code in step 26 for diffusion term will make the advection boundary conditions redundant.

{
 BoundaryValues<dim> boundary_values_function;
 boundary_values_function.set_time(time);

 std::map<types::global_dof_index, double> boundary_values;
 VectorTools::interpolate_boundary_values(dof_handler,
 0,
 boundary_values_function,
 boundary_values);

 MatrixTools::apply_boundary_values(boundary_values,
 system_matrix,
 solution,
 system_rhs);
}

 Am I missing anything? How do I handle the boundary conditions in dealii for advection term?

[Praveen C]

For an advection-diffusion equation you have to specify boundary conditions everywhere on the boundary. You have to decide what boundary conditions you want, dirichlet, neuman, or some mixture of these. Also you have just one boundary condition for the pde, there is no separate advection boundary condition and diffusion boundary condition.

Best

Praveen

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