“…For CFD research in this special issue, a sludge thermal drying process was numerically simulated using a coupled CFD-DEM approach, and the optimal operating conditions were determined with flexibility recommendations for dryer design summarized. 5 The improvement and development of numerical methods are also one of the key topics of CFD research. Li et al 6 developed a novel numerical method that was proposed by introducing a refined-grid model and a coarse-grained model into the unresolved discrete element method and volume-of-fluid (VOF) method to solve inflexibility of selecting grid size for gas−liquid-flow simulations.…”