Drop Formation in Non-Newtonian Fluids

Abstract

We study the pinch off dynamics of droplets of yield stress and shear thinning fluids. To separate the two non Newtonian effects, we use a yield stress material for which the yield stress can be tuned without changing the shear thinning behavior, and a shear thinning system (without a yield stress) for which the shear thinning can be controlled over a large range, without introducing too much elasticity into the system. We find that the pinch off remains very similar to that of constant viscosity Newtonian liquids, and consequently thinning in shear flow does not imply a thinning in elongational flow.

Slow flows of yield stress fluids: yielding liquids or flowing solids?

“…This assumption appears to be in agreement with existing measurements (Yoshitake et al 2008, Jalila and Coussot 2013, Aytouna et al 2013, Jorgensen et al 2015. It remains that a direct measure of interfacial tension with YSF is a challenge because, in such materials, there might exist, even at rest, residual stresses which can preclude a straightforward appreciation of interfacial stresses.…”

Drop formation in shear-thickening granular suspensions

“…For instance, theoretical analysis predicts that the drop breakup in shear thinning fluids proceeds faster than that in the Newtonian case due to the high elongational rates present in the fluid neck during the thinning [14,15]. To the contrary, experiments show that in shear thinning and very strongly shear thinning yield stress fluids, the breakup dynamics can be described completely by the equations for the breakup of simple fluids [6], whereas other experiments do report a signature of the shear thinning behavior [7,16,17]. A very recent paper shows that nonlocal rheology may play a role in these yield stress fluids [18].…”

“…1(a) inset] and this happens at a larger scale instead of a single-particle level. The asymmetry coefficient defined in [6,26] shows a clear and sharp transition from asymmetric to symmetric breakup around ϕ ≈ 45% [ Fig. 1(b)].…”

“…On the other hand, drop formation in non-Newtonian fluids, which is important in areas such as emulsification, inkjet printing, and agricultural spraying, is still ill understood in many cases [1][2][3][4] and continues to attract considerable attention [5][6][7][8][9][10][11][12][13]. For instance, theoretical analysis predicts that the drop breakup in shear thinning fluids proceeds faster than that in the Newtonian case due to the high elongational rates present in the fluid neck during the thinning [14,15].…”

Nonuniversality in the Pinch-Off of Yield Stress Fluids: Role of Nonlocal Rheology

“…We make use of two experimental setups, in order to address recent conflicting literature results on the breakup dynamics of yield stress fluids, raising questions as to what controls this dynamics [11,15]. The first experimental setup probes the breakup of a liquid bridge initially squeezed between two glass plates.…”