Sorry I realized that image is unhelpful without what it is supposed to be. It should be a straight, flat line of zero values. Now attached is the same image but with the correct value plotted too as a black line.
Best, Sean On Wednesday, July 17, 2024 at 4:38:12 PM UTC-6 Sean Johnson wrote: > Hey, > > I am trying to solve a few coupled hyperbolic equations using > discontinuous galerkin finite elements. > > In one of my test cases there are oscillations forming. I tracked it down > to the gradients of variables that are set to 1 everywhere by: > > > VectorTools::interpolate(mapping,dof_handler_DG,Functions::ConstantFunction<dim>(1.),alpha_solution); > > Obviously changing the final vector for different variables. > > Later, when the gradient of these terms are used the gradient calculated > by deal.ii is not 0. I do get very small values on the order of 10^(-14) > and when I account for the inverse jacobian factor the unit_gradient > returns values ranging between +/- .9x10^(-15) & +/- 2x10^(-15). > > These seem very small but due to their values being periodic they quickly > grow and destroy stability of my simulation. Are there any known fixes for > this? > > I haven't noticed any oscillations in the values of the variables from > using VectorTools::interpolate for setting initial conditions that would > obviously lead to oscillations in the gradient. > > Attached is an image on paraview of another variable that depends on one > of these oscillating gradients. It has been scaled up by a factor of > ~10^(11) > > Thanks for your time and any help you can provide, > Sean > -- 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/f62ea9c8-2669-4c21-80db-52dcaaa4657en%40googlegroups.com.
