"Experimental studies of the flow of concentrated hard sphere suspensions into a constriction
Lucio Isa, Rut Besseling, Eric R. Weeks, and Wilson C. K. Poon, J. Phys.: Conference Series 40, 124-132 (2006).

Interesting flow properties are observed when a concentrated suspension of colloidal particles flows into a geometrical constriction. We present here a description of two different experimental techniques used to study the pressure driven flow of dense suspensions of micron-sized hard spheres into glass capillaries. The first one involves the analysis of the driving pressure during the flow, the other one is based on fast confocal microscopy. Technical details are given, together with a selection of preliminary results.