Howdy, I was trying to test an eddy viscosity model for an internal flow problem with heat transfer - set up very similar to turbChannel. The domain contains a stagnating region, from which the attached picture shows a slice (flow in x from left, wall at bottom and right side is also wall, the flow goes around this cylinder in/out of the in-plane/y-direction). The viscosity computation kicks in after the 2nd time step, before that diffusivity is just equal param(2) (rho is unity). What happens though is that as soon as I start the simulation with uservp (param 30 > 0), the velocity goes nuts in the stagnation region, starting from step 0, even though viscosity does not (yet) change. After some debugging, I found that this behavior is caused by the following line which I took from turbChannel: "if(ifsplit .and. param(30).gt.0) ifexplvis = .true." ifsplit is true in my case, so this condition is met and yields the weird behavior as seen in the plot. When I comment it out, however, everything seems normal and even the eddy viscosity computation seems to work well, although I haven't done long term testing yet. What would you advise me to do? I am using rev548. Thanks, Markus