Wall slip and bulk flow heterogeneity in a sludge under shear

• DOI: 10.1007/s00397-024-01479-3
• Publication Date: 2025-01-14T00:59:39Z
• Authors: Sébastien Castel; Arnaud Poulesquen; Sébastien Manneville
• Keywords: yield stress; Slurry; [SPI] Engineering Sciences [physics]; Soft Condensed Matter (cond-mat.soft); FOS: Physical sciences; Condensed Matter - Soft Condensed Matter; slip; flow heterogeneity; [PHYS.COND.CM-SCM] Physics [physics]/Condensed Matter [cond-mat]/Soft Condensed Matter [cond-mat.soft]

Abstract We investigate the shear flow of a sludge mimicking slurries produced by the nuclear industry and constituted of a dispersion of non-Brownian particles into an attractive colloidal dispersion at a total solid volume fraction of about 10 %. Combining rheometry and ultrasound flow imaging, we show that, upon decreasing the shear rate, the flow transitions from a homogeneous shear profile in the bulk to a fully arrested plug-like state with total wall slip, through an oscillatory regime where strong fluctuations of the slip velocity propagate along the vorticity direction. When the shear stress is imposed close to the yield stress, the shear rate presents large, quasi-periodic peaks, associated with the propagation of local stick-and-slip events along the vorticity direction. Such complex dynamics, reminiscent of similar phenomena reported in much denser suspensions, highlight the importance of local flow characterization to fully understand sludge rheology.