An investigation of pulsed fluidization by discrete element method simulation is presented. The particles used were 0.5 mm in diameter and 2650 kg/m(3) in density. The pulsed gas flow consisted of a fluctuating component superimposed on a constant component. The effect of gas pulsation was assessed through examination of bed pressure drop and bubble patterns for a wide range of conditions. The influence on fluidized bed behaviour of frequency and amplitude of pulsation, superficial gas velocity of the base flow, and the nature (type) of pulsation was studied. Transition from chaos to ordered behaviour and formation of regular bubble patterns were reproduced. It was found that regular bubble patterns arise from periodical formation of horizontally aligned voids near the distributor plate. (c) 2005 Elsevier B.V All rights reserved.