Paper by Washino et al. is now accepted for publication in Powder Technology.
"Time Step Criteria in DEM Simulation of Wet Particles in Viscosity Dominant Systems", Kimiaki Washino, Ei L. Chan, Koki Miyazaki, Takuya Tsuji & Toshitsugu Tanaka, Powder Technology (in press)
http://dx.doi.org/10.1016/j.powtec.2016.08.018