Correctly setting initial conditions using Expression() in DG problem

[dokken]

Make a manual projection operator, as nate suggests.
See for instance:

How to plot normal unit vector of faces in a 2D mesh?

Not sure what you mean by pre-defining the direction? Anyhow. You do not use your cell-function in this case, which does not restrict your normal as it should. Here is an example where i compute the normal between two interface. Changing res from “+” to “-” will change the direction of the normal as described in: from dolfin import * import numpy as np # define the subdomains class Circle(SubDomain): def inside(self, x, on_boundary): return x[0]**2 + x[1]** 2 <= 0.5 # Create m…