Dear Professor Wolfgang, Thank you very much for your answer. This is exactly what I wanted to confirm. I highly appreciate it.
Best, Najwa On Thursday, April 24, 2025 at 5:10:50 PM UTC+3 Wolfgang Bangerth wrote: > > Najwa: > if you have a discontinuous viscosity in the Stokes equations, I think you > want to read this paper: > https://www.math.colostate.edu/~bangerth/publications/2017-boussinesq.pdf > Specifically, section 3.3 talks about this situation, and it shows in > figures > 2 and 4 that you do get spikes in the pressure. > > Best > W. > > > On 4/24/25 05:17, Najwa Alshehri wrote: > > *** Caution: EXTERNAL Sender *** > > > > Dear team, > > > > I am seeking your help in understanding how few things work in dealii. > > > > I am solving Stokes interface problem where viscosity differs in two > parts of > > the domain ( outer part and immersed circle). I am solving using > unfitted > > boundary approach ( boundary between domains do not align with the > mesh). I am > > using Q2-Q1 Finite element. > > > > I use the following data_out: > > std::vector<std::string> solution_names(dim, "velocity"); > > solution_names.emplace_back("pressure"); > > > > std::vector<DataComponentInterpretation::DataComponentInterpretation> > > data_component_interpretation( > > dim, DataComponentInterpretation::component_is_part_of_vector); > > data_component_interpretation.push_back( > > DataComponentInterpretation::component_is_scalar); > > > > const MappingQ<dim> mapping(1); > > > > DataOut<dim> data_out; > > data_out.attach_dof_handler(dof_handler); > > data_out.add_data_vector(error_u, "error_u"); > > data_out.add_data_vector(error_p, "error_p"); > > data_out.add_data_vector(solution, > > solution_names, > > DataOut<dim>::type_dof_data, > > data_component_interpretation); > > data_out.add_data_vector(error_per_cell_omega, "error_indicator_omega"); > > data_out.build_patches(mapping, fe.degree + 1, > DataOut<dim>::curved_inner_cells); > > > > > > I removed the mean value of the approximated pressure in different ways. > One > > of them is just like in step-56 > > const double mean_pressure = VectorTools::compute_mean_value( > > dof_handler, QGauss<dim>(2 * pressure_degree + 10), solution, dim); > > solution.block(1).add(-mean_pressure); > > > > > > I noticed that the solution of the pressure have some (unexpected) > > oscillations at the interface even though the exact solution of the > pressure > > is a smooth function (x^2-y^2). In fact, if I just look at the solution > in 2d > > using heat map, those oscillations are not clear. > > > > 2d_p.png > > However, in ParaView, when I use Warp by a scalar filter, they are so > clear. > > 3d_p.png > > > > > > My questions are, > > Is this "compute mean value" works with any order of finite element? > > Am I using "build batches" wrong? > > Is this a common behaviour if the coefficients jumps? > > > > Any other suggestions are appreciated. > > > > Thank you so much, > > Najwa > > > > > > > > > > > > -- > > The deal.II project is located at http://www.dealii.org/ > > <http://www.dealii.org/> > > For mailing list/forum options, see > > https://groups.google.com/d/forum/dealii?hl=en > > <https://groups.google.com/d/forum/dealii?hl=en> > > --- > > You received this message because you are subscribed to the Google > Groups > > "deal.II User Group" group. > > To unsubscribe from this group and stop receiving emails from it, send > an > > email to [email protected] > > <mailto:[email protected]>. > > To view this discussion visit > > > https://groups.google.com/d/msgid/dealii/d9a8c115-f363-42b5-bef2-9b26b62ae616n%40googlegroups.com > > < > https://groups.google.com/d/msgid/dealii/d9a8c115-f363-42b5-bef2-9b26b62ae616n%40googlegroups.com?utm_medium=email&utm_source=footer > >. > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: [email protected] > www: http://www.math.colostate.edu/~bangerth/ > > > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/dealii/357f36e8-f4ca-4b72-84cb-6ab439d6f627n%40googlegroups.com.
