Overset Mesh is one of the coolest technologies in STAR-CCM+ as it allows objects to move around your computational domain freely without tying your mesh in knots, be that an overtaking car, an excavator arm, or the complex multiple motions involved in a production line. The motion does not even have to be prescribed, the Dynamic Fluid Body Interaction (DFBI) model allows you to solve for motion, in six degrees of freedom or less, based on the forces and moments acting on a body, such as a boat on a free surface, or a ball in a ball valve. To date, however, there has been one major constraint when using Overset Mesh, namely that all gaps had to be resolved with at least 2-4 cells, however small the gap, for Overset Mesh to work correctly. This limitation meant that for some cases with very small gaps, users had to choose between excessive cell counts or increasing the gap size in an unphysical manner.
The upcoming release of STAR-CCM+ v9.06 removes that constraint with the introduction of gap handling for Overset Mesh via the new “Zero Gap” Interface type.