Always some errors are left after I wrote the message... errare humanum est. I inversed the figure in the text, I meant :
"On the fig. 5, the bottom right cell has its form function different than 0 for dof =0 (angle dof) (i.e *fe_face.shape_value(dof = 0; point_gauss) =/= 0* ) whereas on the fig. 4, the bottom left cell has *fe_face.shape_value(dof = 0; point_gauss) *= 0 for all gauss point. Also when I wrote "The BC", I wanted to say that the boundary conditions are the same in both cases and are actually implemented directly in the assembly (like in step-12). El miércoles, 6 de octubre de 2021 a la(s) 17:36:29 UTC+2, Sylvain Mathonnière escribió: > Dear all, > > I am experiencing a symmetry issue in my calculation with certain set of > parameters. > In the 3 figures below, I used different sets of parameters (same > equation) and plotted the result once the simulation reaches steady state. > The two first figures look fairly symmetric (as it should be) but the 3rd > one is obviously not symmetric. > Upon closer inspection, one can see that the bottom left corner looks a > bit "shaky" on the first 2 figures. > > [image: fig1_3.PNG] > > I tried to get to the bottom of why this happens numerically ? > I found that at some point during my assembly of the RHS, there is a > difference in what I obtained even though it should be perfectly symmetric. > The solver takes also significantly longer to solve it. > I represented the RHS on a coarse grid to highlight the difference. > > [image: fig4_5.PNG] > > By digging even more I realised that the discrepancy steams from the > boundary_worker (similar to the one of step-12). > On the fig. 4, the bottom right cell has its form function different than > 0 for dof =0 (angle dof) (i.e *fe_face.shape_value(dof = 0; point_gauss) > =/= 0* ) > whereas on the fig. 5, the bottom left cell has *fe_face.shape_value(dof > = 0; point_gauss) *= 0 for all gauss point. > > For the record, I am solving several time the radiative transport equation > I using the discontinuous galerkin method using several directions. > [image: RTE.PNG] > So the fig.4 is the RHS for one direction beta=(0.14; 0.14) and fig 5. is > the RHS for the other direction beta=(0.14;-0.14). The BC > > *My question is the following: * > Is this a normal behaviour that I am experiencing and the lack of symmetry > in fig. 3 is linked with the fact that my mesh is not fine enough ? > or could it be the result of something wrong in my code (I attached a > snipset of it below) ? > > I am not experienced enough to know the difference. I know the code works > well because I compared it to scientific reference + using the method of > manufactured solution, so if there is a mistake, it has to be "small". > > Best regards, > > Sylvain Mathonnière -- 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 on the web visit https://groups.google.com/d/msgid/dealii/dda13b58-6234-45bd-8a29-3fbf0d7e6ae3n%40googlegroups.com.
