Dear all:

I am new to fenics, and I wonder if it’s possible to find the gradient w.r.t the MeshFunction?

More specified:

For a given mesh, with stored simulation result from external numerical model, we denote the f_{i} \in R be the value of the i-th mesh center. So we have no explicit expression for f but only mesh-center value.

Consider for the nonlinear poisson problem (g is known function, boundary setting is same as demo nonlinear poisson case), my question is : how we formulate the || \nabla f||^{2}, or gradient of f in fenics, with only information of the mesh and the cell center value ?

Tried solution:

[1] In demo case ‘tensor weighted poisson’, an example of the meshFunction may solve this problem. However, it reports that '‘MeshFunctionDouble can not be converted to any UFL type’ .

Thanks for anyone watched this thread.

Best regards,

Anthony