On the Role of Critical Strain in Particle Resuspension Dynamics

Resuspension of solid particles in fluids is a fundamental transport phenomenon with broad implications across natural and engineered systems, including sediment transport, riverbed erosion, biogeochemical cycling, and industrial mixing. Despite its significance, accurately predicting the onset and dynamics of resuspension remains a challenge.

In this study, we investigate the resuspension behavior of non-Brownian spherical particles in a Newtonian fluid subjected to both steady and oscillatory shear flows. Through rheological measurements and in situ rheo-microscopy across a wide range of particle volume fractions (ϕ = 0.30 to 0.55), we demonstrate that strain, not shear rate, is the primary parameter governing both the onset and progression of resuspension.

Our results reveal a consistent, strain-driven transition from a quiescent sediment bed to a fully suspended state, facilitated by effective particle collisions and collective motions. We further develop a theoretical model that quantitatively links critical resuspension strain to particle volume fraction, enabling the construction of predictive state diagrams that delineate sedimentation, resuspension, and fully suspended regimes under different shear conditions.

These findings provide a unified framework for understanding and predicting particle resuspension in dense suspensions, offering valuable insights for a wide range of applications in geophysical flows, environmental transport, and industrial processes.