I am writting the poisson code with variable co-efficient in fenicsx a\Delta u=f(x) where a=a(x) variable coefficient. Could you please suggest something

See How to implement a varying coefficient in the bilinear form?

Can there be any simple case where a(x)= x? In Expression this was working a = Expression(x[0], degree=1)

No, this I was using in fenics. Now I am writting in fenicsx. So, this Expression is not working there. Could you please help?

This is covered many times in the dolfinx demos and the dolfinx tutorial The FEniCSx tutorial — FEniCSx tutorial A simple edit of https://github.com/FEniCS/dolfinx/blob/main/python/demo/demo_poisson.py adding the lines A = x[0] + 1 a = inner(A * grad(u), grad(v)) * dx fulfils your example. impor…

I have tried both the ways that you suggest. This is the minimal 1D code I have written to compute L2 norm. For constant coefficient I am getting results. But not for variable. Could you please check? from mpi4py import MPI from dolfinx import mesh import numpy as np from math import * from dolfinx…

see, e.g., Error control: Computing convergence rates — FEniCSx tutorial

Thank you. It is working now with variable coefficient, but my doubt is in 2D coefficient A has be to be in matrix form. How to define that A as matrix here? import ufl import numpy as np from mpi4py import MPI from petsc4py import PETSc from dolfinx.fem import (Expression, Function, FunctionSpace,…

Consider User-defined expression for tensor coefficient .

Poisson with variable co-efficient

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dokken July 29, 2023, 6:52am 11

As you are using dolfinx, consider for instance Speeding up time-dependent diffusion equation - #4 by dokken

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Poisson with variable co-efficient

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