  The recently developed level-set-DEM is able to seamlessly handle arbitrarily
shaped grains and their contacts through a discrete level-set representation of
grains' volume and a node-based discretization of their bounding surfaces.
Heretofore, the convergence properties of LS-DEM with refinement of these
discretizations have not been examined. Here, we examine these properties and
show that the original LS-DEM diverges upon surface discretization refinement
due to its force-based discrete contact formulation. Next, we fix this issue by
adopting a continuum-based contact formulation wherein the contact interactions
are traction-based, and show that the adapted LS-DEM is fully discretization
convergent. Lastly, we discuss the significance of convergence in capturing the
physical response, as well as a few other convergence-related topics of
practical importance.
