Paper Number
SC21 

Session
Suspensions, Colloids, and Granular Materials

Title
Unifying disparate non-Newtonian regimes in suspensions: One model to unify them all

Presentation Date and Time
October 12, 2021 (Tuesday) 1:55

Track / Room
Track 5 / Ballroom 6

Authors (Click on name to view author profile)

1. More, Rishabh V. (Purdue University, Mechanical Engineering)
2. Ardekani, Arezoo M. (Purdue University, Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Rishabh V. More and Arezoo M. Ardekani
Mechanical Engineering, Purdue University, WEST LAFAYETTE, IN 47906-3276

Speaker / Presenter 
More, Rishabh V.

Keywords
computational methods; colloids; non-Newtonian fluids; suspensions

Text of Abstract
A typical dense non-Brownian particulate suspension exhibits a strong non-Newtonian behavior even if the suspending fluid is Newtonian. Here we present a numerical framework based on discrete particle dynamics and rooted in fundamental physics of microscopic inter-particle interactions like hydrodynamic, attractive/repulsive DLVO and non-DLVO (Derjaguin and Landau, Verwey and Overbeek), the inter-particle contact, and friction to quantitatively predict this non-Newtonian behavior in suspensions. Specifically, a suspension undergoes shear thinning (decreasing viscosity) at low shear rate/stress followed by a Newtonian plateau (constant viscosity) at intermediate shear rate/stress values which transitions to shear thickening (increasing viscosity) beyond a critical shear rate/stress value and finally, a second shear thinning transition is observed at extremely high shear rate/stress values. We unify and quantitatively reproduce all the disparate non-Newtonian regimes and the corresponding transitions with increasing shear rate/stress for the first time. Direct comparison with experimental data from the literature corroborate the validity of the proposed numerical method. Inclusion of traditional hydrodynamic, attractive/repulsive DLVO forces, the inter-particle contact forces and a constant friction reproduce the initial thinning as well as the shear thickening transition consistent with the previous studies. However, to quantitatively capture the intermediate Newtonian plateau and the second shear thinning, an additional non-hydrodynamic interaction of non-DLVO origin and a decreasing coefficient of friction, respectively, are essential; thus, providing the first explanation for the presence of the intermediate Newtonian plateau along with reproducing the second shear thinning in a single framework. We also demonstrate the capabilities of the proposed framework in capturing other non-Newtonian behaviors such as thinning – thickening, thinning – thickening – thinning, normal stress differences along with the effect