To evaluate the hydrodynamic performance of the grid zone for a fluidized bed when distributors of different open-area ratios are used, solid holdup signals were sampled from a 2D cold-model column by an optical fiber system. Both time and frequency parameters were extracted from the raw signals to rank the distributors. Different criteria based on these parameters often gave different (even contradictory) rankings; hence a weighted scoring scheme was adopted, taking into consideration both time and frequency domain criteria as a simple tool to evaluate and compare alternative distributors. The scheme gave a reasonable compromise among such criteria as solid holdup signals, fundamental frequency and zero-crossing time of solid hold up signals. Based on the quantitative scoring scheme, the best geometry was chosen among the five alternatives tested. (C) 2011 Elsevier B.V. All rights reserved.