AbstractThe characteristics of a gas–solid fluidized bed are influenced by complicated and stochastic phenomena, e.g. jetting and the bubbling of the fluidizing medium and the motion of the fluidized particles. In this study pressure fluctuations due to the bubble movement were measured by means of a pressure probe over a range of time. The resultant time series have been analysed by determining their autocorrelation function and power spectrum with emphasis on the examination of the effect of the superficial velocity of the fluidizing gas. A stochastic model of bubble motion in a fluidized bed has been developed. This model visualizes the bubble motion in a fluidized bed to consist of the random movement, generating irregular signals, and the linear movement, generating wave‐like signals. A theoretical autocorrelation function and a power spectral density function have been derived based on the mo