Abstract: This study focuses on investigating the passive regulation of particle clusters in fluidized bed risers with internal rings using a two-fluid model (TFM) combined with the kinetic theory of granular flow (KTGF). A computational cell-based dynamic cluster structure-dependent (DCSD) drag model is adopted to predict the cluster characteristics. The impact of ring internals and superficial gas velocity on cluster characteristics differs across six sections divided by five ring internals in the riser. The opening ratio of the ring internals plays a crucial role in determining cluster characteristic, with different behaviors observed at different superficial gas velocities and axial positions in the riser. The cluster number fraction reaches its maximum value at an 80% opening ratio and remains constant as the opening ratio increases at superficial gas velocity of 4 m/s. As the superficial gas velocity increases, the cluster number fraction increases with the enlargement of the opening area.