  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.
