Confinement Induced Segregation Effects in Suspension Rheology

The formation of a particle depleted and a structured particle layer adjacent to a confining surface is a well known effect in suspension rheology. This thesis aimed to provide insight into specific properties of these layers. Firstly, the influence of pressure on the depleted layer, which is the cause of apparent wall slip, should be quantified. A slit die was fitted with pressure transducers and an outlet restrictor. By performing experimental work as well as simulations, it was demonstrated that the pressure's influence is negligible. Secondly, a setup should be provided, which allows for the characterization of both depleted and structured layers with regard to various, independently variable, parameters. To this end, a parallel plate rheometer was modified for optical accessibility. Optical velocimetric and concentration determination methods were implemented. After carefully mapping the modification induced distortion of the velocity field, concentration profiles were obtained and analyzed. Especially the demonstrated vertical concentration gradient poses a new challenge for rheology.