Using ufl for manifactured solutions

[dokken]

The interface to interpolate ufl-expressions is not quite as you tried to use it.

You need to use dolfinx.fem.Expression as a wrapper around the ufl-expression.

This is shown of in various places:
https://jsdokken.com/dolfinx-tutorial/chapter1/membrane_code.html?highlight=fem+expression#interpolation-of-a-ufl-expression
https://jsdokken.com/dolfinx-tutorial/chapter4/convergence.html?highlight=fem+expression#reliable-error-norm-computation
https://jsdokken.com/fenics22-tutorial/heat_eq.html#post-processing-without-projections

Interpolate expression with complex litteral

Hello, I am not sure why, but the following MWE does not work import dolfinx, dolfinx.mesh from dolfinx import fem from mpi4py import MPI mesh = dolfinx.mesh.create_unit_cube(MPI.COMM_WORLD, 5, 5, 5) V = fem.FunctionSpace(mesh, ("CG", 1)) u = fem.Function(V) u.vector.set(0.) f = fem.Function(V) expr = 1j * u f.interpolate(fem.Expression(expr, V.element.interpolation_points)) which yields the following error TypeError: can't convert complex to float This is actually not a very big deal, …

Evaluate ufl expression, element CFL and Peclet

Hi everyone, it took me ages to figure out the many steps needed to compute a local element-wise ufl expression, in this case CFL and Peclet. can you confirm this is the correct (and easiest way) of doing it? # Compute Peclet and CFL number locally vnorm = ufl.sqrt(ufl.dot(vel, vel)) # local norm of the velocity h = ufl.CellDiameter(mesh) # local mesh size Peclet = h*vnorm/ufl.sqrt(ufl.inner(D, D)/3) # Peclet number cfl = 2*dt*vnorm/h # local time…

How to operate on a fem.Function and maintain type/attributes without interpolating?

Note that Is a ufl-expression. To map a UFL expression to a function space, you need to use interpolate. Specifically, you need to use the u2expr=dolfinx.fem.Expression(u2, W.element.interpolation_points()) and u3 = Function(W) u3.interpolate(u2expr). Is there a specific reason for trying to avoid interpolation? And what is the actual matrix you want to use?