Laurent Jossic

Segregation under flow of objects suspended in a yield stress fluid and NMR imaging visualisation

Abstract This study demonstrates the segregation of spheres suspended in a gelled fluid, in laminar flow, in a sudden expansion. The flow conditions are such that gravity effects are negligible. The spheres are stable in the gel at rest. The upstream pipe diameter is in a ratio of 4:1 to the diameter of the spheres. In these circumstances, the medium is discrete, not continuous. It is shown that the initial conditions and flow kinematics lead to segregation of the matter in the downstream pipe. Nuclear magnetic resonance imaging reveals an organised distribution of the solid matter downstream of the expansion. The effects of volume concentration, geometry and flow velocity were assessed. A model of the phenomenon is proposed.