High-resolution Eulerian simulations are carried out to explore the problem of length scale dependence or filter size dependence in heterogeneous gas-solid two-phase flows. It was found that, with the extension of the simulated domain, the average inter-phase slip velocity or inter-phase drag coefficient and the index of heterogeneity increased initially and then approached asymptotic values, which demonstrates the existence of a scale-independent or filter-size-independent plateau for these properties. (C) 2008 Elsevier Ltd. All rights reserved.