I'm trying to calculate the pressure drop to various ports through a gap between a piston and cylinder. The gap is only 0.002mm wide (radially), but is 30+mm long (on a 6mm diameter piston). Using the standard refinement with 0.002mm as the smallest gap does not work (it doesn't push any flow through the gaps). I've tried narrow channel refinement along the surface of interest, but it never builds a mesh (RAM peaks at 24GB and progress essentially stops). Are there tricks that can be played with the cell aspect ratio or other things that can help? I'd prefer to have 3 cells accross the gap but have a suspicion that the software won't be able to help me with this particular problem.

On a similar note, is there a rough Cell/Memory ratio for figuring out what the largest problem size can be run given a certain amount of RAM?