Paper Number
SC24 

Session
Suspensions, Colloids and Granular Media

Title
Why not friction and hydrodynamics? A generalized model of the dynamics and structure of dense colloidal suspensions

Presentation Date and Time
February 14, 2017 (Tuesday) 3:35

Track / Room
Track 1 / Audubon B

Authors (Click on name to view author profile)

1. Maia, Joao (Case Western Reserve University, Macromolecular Science and Engineering)
2. Boromand, Arman (Case Western Reserve University)
3. Grove, Brandy (Case Western Reserve University)
4. Jamali, Safa (Massachusetts Institute of Technology)

Author and Affiliation Lines (in printed abstract book)
Joao Maia¹, Arman Boromand¹, Brandy Grove¹, and Safa Jamali^2
1Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7202; ²Massachusetts Institute of Technology, Cambridge, MA 02139

Speaker / Presenter 
Maia, Joao

Text of Abstract
We perform mesoscopic DPD simulations incorporating both hydrodynamic and frictional interparticle interactions to study the effect of interaction potential on the rheology and structure of dense frictional colloidal suspensions. In particular, we performed a series of viscosity and normal stress measurements in suspensions with different volume fractions and obtained, for the first time, a complete picture of the dynamic state and of the microstructure. We confirmed that N1 for semi-dense suspensions stays negative and grows with shear rate, which is consistent with hydrocluster-induced shear-thickening. We show that continuous shear-thickening, CST, in colloidal suspensions can be explained solely via hydrodynamics, frictional bonds being transient and negligible to the rheological response. In dense suspensions and close to the jamming transition however, friction is required to obtain DST and replicate the recently experimental findings of a transition from negative to positive N1. We prove that hydroclusters form first at low stresses; this brings the particles together, thus allowing frictional contacts to develop, eventually leading to discontinuous shear-thickening, DST. In addition, when each particle is subject to an average of one frictional contact, N1 reverses its increase but remains negative; at approximately two frictional contacts, a percolating network forms and N1 becomes positive.