Development of a thixotropic fluid flow in a pipe

This paper deals with the interaction between the modifications of the inte rnal structure of a thixotropic fluid and the flow development along a pipe . The experimental set-up consists of a pipe, where a flow of thixotropic f luid is provided from a large vessel. The axial velocity distribution was d etermined using particle image velocimetry technique and ultrasonic velocit y profile monitor. At the entrance section, the fluid is assumed to be in a homogeneous structural state corresponding to a high shear rate. The exper imental results show a progressive flatness of the velocity profiles due to the aggregation of the structural elements of the fluid. The flow evolutio n is governed essentially by the kinetics of aggregation and segregation si nce the associated time scales are longer than the relaxation time of the f low.