dear users, I've read this page about modelling a gear pump: http://www.cfdreview.com/article.pl?.../11/13/2049238

I'm not able to understand how it was possible to avoid negative volume in that simulation. Cells seem to slide or to change topology but how is it possible to do this? Could someone help me to understand?

best regards, Alex

Hi,

The minimum clearance between the gears is 0.5mm, which is an order of magnitude greater than the real gear. This means they just squash the mesh up into this 0.5mm. Therefore no topology change is required.

Also it was done in TASCFlow, not CFX5/10/11 but I don't think TASCFlow allows topology changes either.

Glenn Horrocks

thanks for the reply, I agree with you about the mesh just squashed up (in fact images on the web pages seem to show this) but I'm not able to understand what kind of boundary conditions were used. To be more precise, if a node is constrained to the internal gear and it is linked with a node of the external gear, after 1 revolution this connection should involve a mesh distorsion and negative volume elements. This because if the internal gear completes 1 revolution, the external is in delay by means of the difference in the number of tooth. The mesh on the images seems to slide instead...but what kind of boundary condition is this?

thanks for any advice