Dilute sedimenting suspensions of spheres at small inertia

The sedimentation dynamics of a dilute suspension of non-Brownian spheres is experimentally examined at small particle Reynolds numbers but at Reynolds numbers based on the container size extending up to the small-but-finite inertial regime. While the long-time velocity fluctuations are independent of the Reynolds number in the Stokes regime, they are seen to decrease with increasing Reynolds number above a critical container Reynolds number of approximately , and more precisely to vary as a power of the Reynolds number. The microstructure of the suspension is also seen to evolve with increasing Reynolds number and to depart from random positioning as it becomes more sub-homogeneous and disordered.

Automated summary

In this study, the authors experimentally examined the sedimentation dynamics of a dilute suspension of non-Brownian spheres at small particle Reynolds numbers and up to the inertial regime. They found that long-time velocity fluctuations are independent of Reynolds number in the Stokes regime, but decrease with increasing Reynolds number above a critical value, following a power-law relationship. Additionally, the microstructure of the suspension was observed to become more sub-homogeneous and disordered as Reynolds number increased.