Using Acoustic Perturbations to Dynamically Tune Shear Thickening in Colloidal Suspensions

Abstract

Colloidal suspensions in industrial processes often exhibit shear thickening that is difficult to control actively. Here, we use piezoelectric transducers to apply acoustic perturbations to dynamically tune the suspension viscosity in the shear-thickening regime. We attribute the mechanism of dethickening to the disruption of shear-induced force chains via perturbations that are large relative to the particle roughness scale. The ease with which this technique can be adapted to various flow geometries makes it a powerful tool for actively controlling suspension flow properties and investigating system dynamics.

Constitutive model for shear-thickening suspensions: Predictions for steady shear with superposed transverse oscillations

“…For friction-dominated systems (Π Π * ) this protocol has been shown capable of drastically reducing the mean viscosity, in some cases unjamming systems whose viscosity would otherwise be infinite [21,22]. This protocol may find utility in active rheology control [24] for various industrial applications. Because of its strong influence on time-dependent suspension microstructure, it provides a range of stringent tests for any constitutive model.…”

“…In order to arrive at tractable expressions for the suspension microstructure and stress [Eqs. (24,35)], we have replaced the factor a(r − 2a) −1 with its averaged value C 2 , which is taken to obey the Krieger-Dougherty form [11]:…”

“…Eqs. (9,21,24,29,35,37,40) form a closed system for the microstructure and stress. For any given volume fraction φ, the model contains parameters α 0 , β 0 , χ 0 , Π * , φ J 1 and φ J 2 .…”

“…The mechanism behind the loss of contacts has been explained from the perspectives of force chain dynamics [21] and random organisation [22]. Transverse shear flow oscilla-tions may enhance suspension flow in practical applications [24]. In addition, this flow configuration also offers a subtle and challenging test case for constitutive models for suspension microstructure and stress.…”

Universal scaling of shear thickening transitions

“…Changes to φ 0 can be generated by modifying particle roughness [29][30][31][32][33][34]39], shape [40][41][42], and polydispersity [43,44]. Finally, differences in C(φ) may result from the constraints governing particle displacements and ro- tations as well as other perturbations to the flows [25,[45][46][47][48][49][50][51][52]. Thus, differences in these variables directly inform the types of changes that one can use to influence the thickening and jamming behaviors.…”