Dear Lorenzo, Thanks for your interest. Below some answers to your questions
BR Kostas On Thu, Oct 21, 2021 at 12:47 AM Lorenzo Ferro <lorenzo.i...@gmail.com> wrote: > Dear All, > > I've started testing the GeFEM library and I've some questions, with > particular reference to the Python interface (the only one I can use so > far): > > 1) the "add_lumped_mass_for_first_order_brick" method is not available > even though it is mentioned in the Python-Model guide for GetFEM 5.4. I've > installed the precompiled 5.4 version for Windows with > getfem5.4win-amd64-py3.7.exe. How can I get the Lumped_Mass feature for the > Python interface? > The scripting language interface for this function has been added after the last release: https://git.savannah.nongnu.org/cgit/getfem.git/commit/interface/src/gf_model_set.cc?id=0241496a72624aca5f7f6a4f3725accee863d46e so you will have to wait for the next release or compile GetFEM yourself. > 2) The documentation of bricks like "Generic Elliptic Brick", > "Fourier_Robin Brick" and "Source Term Brick" states that the coefficients > could be arbitrary GWFL expressions. What happens if I'd input non-linear > coefficients? How the software manages the assembly in this case? Or, it > would be better to use the Model method "add_non_linear_term"? > Just use the add_linear_term or add_nonlinear_term for this. E.g. The add_fourier_robin_brick is just a convenience function calling add_(non)linear_term for you [image: image.png] Such bricks made sense before the introduction of GWFL, nowadays you should just use add_linear_term or add_nonlinear_term for everything. 3) If I'd like to implement a radiation non-linear boundary condition, what > would be the more advisable way? Is in this case the "add_non_linear_term" > method the correct way? > Yes. If you have a specific equation you want to implement, we can help with writing it in GWFL. > 4) I've not understood what is the difference between "add_source_term" > and "add_source_term_brick". Can you advise when I should use one or the > other (with a practical example). > If I see correctly, providing an expression "expr" and a variable name "var" to the second one is equivalent to providing "expr*Test_var" in the first one. In general you should not use these bricks because they add a contribution to the rhs that is not accounted for in the stiffness matrix computation. Rarely do you need something like this. You can just use "add_linear_term" and "add_nonlinear_term" for everything. > 5) Is there a way to visualize mesh regions for doublecheck purposes? > Maybe, is there a way to export such regions by means of the Python > interface? > Good question. There are different ways, maybe the most simple is something like mf.export_to_vtk("meshregions.vtk", mf, md.interpolation("1",mf,1), 'region1', mf, md.interpolation("1",mf,2), 'region2', mf, md.interpolation("1",mf,4), 'region4') where mf is a (preferably discontinuous) mesh_fem and md is just a model (it can be an empty one). > Thank you in advance for your kind support. > Regards, > Lorenzo >
