Within the stirred-tank flocculating system under equivalent shear-rate cases, the effects of both reactor shape (cylindrical or square) and baffles on floc morphological evolution during flocculation were investigated by applying flocculation tests with the aid of computational fluid dynamics (CFD) simulations. At a constant G(ave), the recirculating times for those floc aggregates existing in water flow to the impeller region and the intensity of turbulence occurring within this region, together with the non-uniform nature of turbulence for water flow above the rotating impeller, were found to be distinct in the various stirred-tank reactors investigated, thereby affecting the development of floc size and structure. Besides, the importance of reactor shape and baffles to floc morphological evolution seemed to be largely determined by predominant growth behavior(s). For aggregation-dominated circumstances, the baffled square stirred tank formed the largest and most compact floc aggregates among all reactors, due to the most visiting times for pre-formed micro-floc aggregates to the highest turbulent-intensity impeller region; while for breakage-dominated circumstances, the most non-uniform distributions of turbulent water flow were generated via impeller baffle interactions in this reactor, thereby giving the highest breakage rate and producing the smallest floc aggregates with the smoothest and most compact structures. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.