Deposition of dispersed and ultradispersed solid particles in cylindrical channels has received considerable attention due to its practical significance and direct application in industry. However, an adequate mathematical expression that studies the separation and suspension of dispersed and ultradispersed particles present in a horizontal cylindrical channel in unsteady state is still missing. In this paper we developed and solved a time-dependent, two-dimensional convective/dispersive model. This model simulates the transient deposition and suspension of dispersed and ultradispersed particles immersed in a stagnant fluid medium inside the cross section of a horizontal cylindrical channel. The results of the modeling are compared with images taken from a series of experiments especially designed for this work. The conditions which permit to control the suspension of the solid particles inside a liquid medium with cylindrical geometry are unveiled by the presented model. The experimen...