Fingering in freeflow test test_ff_stokes2c_densitydrivenflow to be expected?
The freeflow test test_ff_stokes2c_densitydrivenflow
in /test/freeflow/navierstokesnc/densitydrivenflow
shows fingers depending on Newton.MaxRelativeShift. As an example, a comparison of the magnitude of the velocity with Newton.MaxRelativeShift = 1e-14 (left) and Newton.MaxRelativeShift = 1e-8 (right) is shown below:
We should investigate if there is a physical basis for the appearance of fingers in this test.