Hi, i would like to implement a script dependant Neumann BC on Fenicsx 0.7.2. For information the non linear system to solve is the same as : [image] Newton non linear solver with solution dependant neumann condition not converging super well General Hello, i use fenicsx …

[image] katkit: What I want is to, instead of using an explicit mathematical function, use another program to compute the values of g(uh) and apply them at the boundary for each Newton iteration. Then you should either: Use a manual implementation of the Newton iteration where you perform t…

Thanks for answering Francesco, i will implement the interpolation you spoke of this week, and see if it does work as i want. i’ll come back here then

Hello, So I tried my best to implement what I needed, and after some thought I don’t think I need interpolation. • I first need to take numerical values of uh at the Neumann boundary • send them with corresponding numerical x values to my script • then change numerical values in uh at the bounda…

We can’t help anymore unless we have a complete code, i.e. a code we can copy and paste and run. For the sake of increasing the chances of people volunteering their time to read it, please make it as minimal (but still complete) as possible.

ok this is the code for the mesh, just launch it to create the file. #!/usr/bin/env python3 # -*- coding: utf-8 -*- """ Created on Mon Apr 22 15:28:10 2024 """ import sys try: import gmsh except ImportError: print("This demo requires gmsh to be installed") sys.exit(0) from dolfinx.i…

[image] katkit: i can’t really make it smaller Sorry, that’s not true. There are a lot of things you could do to make it smaller: for instance, (1) we don’t need to see your actual mesh, just use a builtin mesh, (2) we don’t need to have the part related to the visualization. This is a forum…

thanks for replying i understand totally, i will create a new one.

As I should have done sooner, i created a minimal working exemple : it’s a square domain, with +1V on top border, and Neumann BC on bottom that is function of u. from dolfinx import default_scalar_type, log from dolfinx.fem import (Constant, Function, functionspace, assem…

[image] katkit: def fct_dens_chrg(x,u): # THE g using numerical Values of uh at Neum bottom boundary g=-13.295*pow(u,2)*np.sign(u) # same as before but with uh values at Neumann bc return g def fct_for_uh(): # this function use fct_dens_chrg(x,u) to change values in ufl uh at Neu…

thanks for the reply, About what i am trying to do with this code : I have made a program with g explicitly using uh, “g= mathematical function of uh”, and it did converge using Newton solver. What I want is to, instead of using an explicit mathematical function, use another program to compute th…

Newton and script dependant Neumann Boundary condition

dolfinx

francesco-ballarin June 7, 2024, 4:18pm 8

And, just to avoid any misunderstanding, I am not making these comments up out of my own mind: see Read before posting: How do I get my question answered?

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Newton and script dependant Neumann Boundary condition

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