Dense suspension is a granular system where a liquid medium fills the interspace between particles. The liquid makes the granular system peculiar in the following ways: Firstly, the liquid contributes to energy dissipation, so the particle dynamics is overdamped. Particle inertia is negligible in typical situations. Secondly, the incompressible nature of the liquid constrains the particle dynamics into a nearly fixed volume; thus, very small submicron granular particles can be confined within the suspension. The confinement also enhances the effect of friction due to persistent contact. In addition, the liquid realizes hydrodynamic interaction and some interfacial interactions, such as electric double-layer forces. In this way, the dense suspension drastically differs from typical dry granular materials. Indeed, they appear like a very viscous liquid. Researchers have evaluated the rheology of such fluids and kept trying to develop constitutive models to predict macroscale flows [1-4]. Such studies still need to be conclusive.  This seminar will explain our DEM-CFD simulation approach and focus on normal stress/pressure and migration in a channel flow of dense suspension, which demonstrates the uniqueness of dense suspension fluid mechanics.
 

[1] M. M. Denn and J. F. Morris. Rheology of non-brownian suspensions. Annu. Rev. Chem. Biomol. Eng., 5(1):203–228, 2014.
[2] C. Ness, R. Seto, and R. Mari. The physics of dense suspensions. Annu. Rev. Condens. Matter Phys., 13(1):97–117, March 2022.
[3] J. J. J. Gillissen, C. Ness, J. D. Peterson, H. J. Wilson, and M. E. Cates. Constitutive model for time-dependent flows of shear-thickening suspensions. Phys. Rev. Lett., 123:214504, Nov 2019.
[4] G. G. Giusteri and R. Seto. Shear jamming and fragility of suspensions in a continuum model with elastic constraints. Phys. Rev. Lett., 127:138001, Sep 2021.

Please contact phweb@ust.hk should you have questions about the talk.