i try to achieve a very simple think (i think..)
i have a pipe and i want to make viscous fluid go through.
but when i activate the collision whith the pipe. my viscosity paramater go away.
in the two video below, is exactelly the same fluid.
anybody already have this problem? how he solved it?

thx a lot

There seems to be something funky with using VDB for collision there, when it's swapped for a regular volume, all is peachy.

The error message it gives you says it all; “No viscosity solve because all fluid was extrapolated into the collision field”.

In other words, reduce Surface Extrapolation under Volume Motion -> Collisions on the FLIP solver. OR, reduce the Particle Separation, which in turn will give you smaller voxels and then the Surface Extrapolation won't have the same radius at the same value.

Skybar
The error message it gives you says it all; “No viscosity solve because all fluid was extrapolated into the collision field”.

In other words, reduce Surface Extrapolation under Volume Motion -> Collisions on the FLIP solver. OR, reduce the Particle Separation, which in turn will give you smaller voxels and then the Surface Extrapolation won't have the same radius at the same value.

Right, that error comes from this change:

Friday, November 15, 2013
Houdini 13.0.235: The Viscosity solver now attempts to detect bad collision fields, which can lead to no viscosity solve or freezing fluids, and issues a warning in that case.

It could probably offer a more useful warning, but this situations typically arises from a “bad” collision field, which in the case of a collision VDB usually means insufficient External Bandwidth. In that case all distance queries return a value inside the extrapolation distance, and the entire field incorrectly looks like it is filled with a collision object.

thanx a lot for your awser guy