A methodology for highly accurate results of direct numerical simulations : drag force in dense gas–solid flows at intermediate Reynolds number

Simulations with an iterative immersed boundary method (IBM) are performed to predict the drag force for gas–solid flows at intermediate Reynolds number (Re). A methodology is developed to obtain highly accurate IBM results at relatively low computational cost. First of all, "resolution-free" gas–solid forces are estimated for a face-centered-cubic (FCC) array of monodisperse spheres in terms of the resolution convergence. This data is subsequently used to compute the relocation of the marker points, so as to correct for the resolution dependence of the simulated force on coarser grids. We then assume that the relocation derived from FCC arrays is also valid for the simulations of random arrays. As a result, the accurate gas–solid forces on random arrays can be obtained from the simulations at a relatively low resolution. We have applied this methodology to predict the gas–solid force at Re = 100 and 50, with ¿¿ varying from 0.1 up to the close-pack limit. The results are consistent with the recently published correlations. A new fit has been proposed for the interaction force at these two specific Reynolds numbers. This methodology makes it feasible to model the dense granular flows of large assemblies at high Re by direct numerical simulations at relatively low computational cost. Keywords : Direct numerical simulation; Immersed boundary method; Methodology; Gas–solid force; Resolution-fre