Help for 3 overlapping grids in overset
 

Hi,

I've read quite a few paper on overset applications involving 1-2 structured o/c-grids with 1 background cartesian grid. The o/c-grids usually do not overlap.

Have anyone succesfully used 3 overlapping grids? ie 2 o/c-grids overlap each other, and they overlap with the background grid.

Supposed there's 2 c-grids of similar density overlapping partially, and a background grid. How should the "holes, donors" be selected that gives the best accuracy/convergence?

Or is it easier to have 1 background cartesian grid, 1 big c-grid, whereby it is fully inside the cartesian grid, and a small c-grid fully inside the previous big c-grid. Will that be better?

Thanks