Giant fluctuations in sheared viscoelastic fluids emerging in a mesoscale simulation

Abstract

Shear flow is known to induce huge density fluctuations in otherwise clear and uniform polymer solutions. This effect is rooted in the elasticity of the entangled polymer network, and can span distances over a thousand chains wide. It has been observed in many scattering experiments, and later explained by mathematical theories.Here we inspect this phenomenon from a direct particle simulation viewpoint. The main novelty is a velocity dependent friction force, coupling the entire system and solved efficiently with sparse matrix algebra. Our minimalist model runs on a desktop PC and the results agree well with experiments.A sugar cube in a cup of tea dissolves faster by stirring with a spoon. In contrast, certain non-Newtonian fluids defy this common sense and become less homogeneous under shear. It is evidenced by a butterfly-shaped scattering pattern of light (SALS) 2 and neutrons (SANS) 3 emerging under a strong deformation. Examples include clay, 4-7 nanoparticle 8 and 1