In addition to the ROI model, Ansys Forte includes an alternative approach to mitigating the mesh dependency of the collision model [91] . This is the collision mesh model, which employs a pseudo cylindrical collision mesh separate from the CFD computational mesh. The collision mesh is based on a cylindrical coordinate system that is coaxial with the spray. To further reduce non-axisymmetry of the predicted spray structure, the collision mesh is rotated at a random angle around the spray axis at every time step. In this method, only parcels in the same collision mesh cell, instead of a CFD cell, are allowed to collide.

Use of the collision mesh model requires specification of the diameter, height, and number of grids along the azimuthal direction of the collision mesh.