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DY: Fachverband Dynamik und Statistische Physik

DY 19: Franco-German Session on Granular Matter I

DY 19.8: Vortrag

Dienstag, 10. März 2026, 11:45–12:00, HÜL/S186

Rheology of dense suspension: the effects of wall-boundaries on viscous-inertial transition — •Alireza Khodabakhshi, Sudarshan Konidena, Franco Tapia, and Bernhard Vowinckel — Institute of Urban and Industrial Water Management, TU Dresden, Dresden, Germany

The transition from the viscous to the inertial regime in dense suspensions is still not fully clarified. Volume-imposed rheometers with fixed-gap walls offer valuable information by reporting shear and normal stress as functions of shear rate, yet the influence of confining boundaries, especially in narrow-gap configurations relevant to industrial and natural flows, remains insufficiently explored. In this study, we perform particle-resolved Direct Numerical Simulations (pr-DNS) of dense non-Brownian suspensions sheared between rough walls in a confined volume-imposed rheometer. The simulations capture the overall viscous-inertial trend reported in recent experiments and reproduce the observed weakening of the effective friction coefficient during the transition. We analyze multiple cases by varying wall roughness and rheometer height, showing that both parameters strongly affect stress levels by altering particle layering. All configurations develop pronounced layering, but the case with the roughest wall and weaker confinement enhances inter-layer mixing, producing higher stress levels. After sufficient strain, this configuration evolves toward a more ordered, low-mixing state, reducing stress to values similar to the other cases. Despite variations in stress magnitude, all cases follow a consistent viscous-inertial transition.

Keywords: dense suspension; viscous-inertial transition; volume-imposed rheology; particle-resolved Direct Numerical Simulations