Fully resolved simulations of flow past fixed assemblies of monodisperse spheres in face-centered-cubic array or random configurations, are performed using an iterative immersed boundary method. A methodology has been applied such that the computed gas-solid force is almost independent of the grid resolution. Simulations extend the previously similar studies to a wider range of solids volume fraction ( phi[0.1, 0.6]) and Reynolds number (Re [50, 1000]). A new drag correlation combining the existed drag correlations for low-Re flows and single-sphere flows is proposed, which fits the entire dataset with an average relative deviation of 4%. This correlation is so far the best possible expression for the drag force in monodisperse static arrays of spheres, and is the most accurate basis to introduce the particle mobility for dynamic gas-solid systems, such as in fluidized beds. (c) 2014 American Institute of Chemical Engineers AIChE J, 61: 688-698, 2015