High-resolution Eulerian simulation has recently emerged as an effective approach for studying the mechanics of heterogeneous gas-solid flow. In this study, it is used to study the characteristics of RMS of solid volume fraction fluctuation and particle clustering structures in a CFB riser. It was shown that the experimentally founded RMS of solid volume fraction fluctuation variation with local mean solid volume fraction can be well predicted and the experimentally measured particle clustering characteristics, including the solid volume fraction inside cluster, cluster time fraction, cluster frequency, cluster existence time, vertical and horizontal cluster velocity and vertical cluster size, can be qualitatively predicted by high-resolution Eulerian simulation. (C) 2008 Elsevier Ltd. All rights reserved.