[okabis]

Hey everyone,


i'm trying to simulate a simple piston, which pushes air into another region.
for an easy start i tried to simulate only the piston in form of a simple cylinder (h=0.715m, r=0.1533m) first.

for the movement i set up a morphing mesh:
- the top with a total linear displacement in y direction, defined by a field function (graph attached). it's supposed to move down and up within 1s

- the walls as floating
- the base is fixed
i didn't change anything in the options for the morphing tool or the morphing solver and used the k-omega turbulence model.

for the mesh, i chose an automated polyhedral mesh with base size 0.02m (picture attached).
as simple as the simulation seems to be, my solution doesn't converge at all (picture attached for 0.05s time step) with residuals up to 1000. i tried time steps from 0.1s to 0.001s, but the finer the step, the worse it gets. changing the mesh didn't do anything either. finer or coarses meshes made no changes. i also tried a trimmed mesh, since i thought it might be better for the morphing, but still no better results...


since the problem itself seems to be quite easy and all changes seem to have no impact, i start to believe, that there must be something wrong in the setup of the morphing...
i hope you guys can help me in any form!



thanks in advance,
okabis




EDIT: well, since i should have put a little less of my concentration on the morphin i should have checked the physics...the problem seems to have been the constant density (of course...). looks like i am not able to delete this thread

[fluid23]

how many inner iterations did you use?

nevermind, I see your edit