Hello.

I want to study the 2D-Backstep flow and for this reason I need to make a dense grid around the step region and a sparse grid in the rest of the area.

How can I do that? How can I define 2 or more different grid characteristics?

I have heard that internal, interior or interface boundary conditions might do the job but still I can't figure out how.

Any help - suggestion will be greatly appreciated.

Thanks in advance, Vasilis.

Hello Vasilis,

I think you've got several options:

You can split up the mesh in different zones with their propre mesh density via the utility tmerge. You can create for example an OCtree-sheme (cartesian mesh, but with different cell dimensions) First you design and mesh each zone seperately in gambit, next you merge them toghether with the utility tmerge (type in the commandwindow of a linux-pc: "utility tmerge -2d") Then he will ask you to append the seperate mesh files from gambit. Next you'll have to fuse the internal zones in fluent (grid -> fuse ..) I gladly refer to the fluent help to find out more on the topic because I've never used it myself.

Another posibility is perhaps the use of an algebraic multigrid scheme on an unstructured mesh Perhaps you also ought to check out the 'grid adaptation' function: this routine refines the mesh within fluent (!) in regions where large gradients (of velocity for example) exist.

kindest regards,

Christof