Mesh moving / ALE in DOLFINx — example or official API

[dokken]

Using a “+” restriction is not correct on an interior facet (as it is arbitrary).
To do a proper, one-sided, oriented integral, see for instance:

Add one-sided integration example as example of custom integration

and

Correct way to compute internal interface fluxes

The key take-away is that: In most finite element methods, the jump of a quantity across a surface does not require a specific orientation. For instance, in DG methods, you get jump integrals across all internal facets of the grids, but mathematically the formulation doesn’t care which cell is positive and which one is negative. DOLFINx follows the same notion, that for an interior facet integral (dS) which cell comes first (+) and which one is last (-) doesn’t matter if put in the correct va…