(247h) Elastic Instabilities of Polymeric Solutions in Cross-Channel Flow

When flexible polymer molecules pass near the hyperbolic point of a microchannel cross flow, they are strongly stretched. As the strain rate is varied at low Reynolds number (<0.01), tracer and particle-tracking experiments show that molecular stretching produces two flow instabilities, one in which the velocity field becomes strongly asymmetric, and a second in which it fluctuates non-periodically in time. These instabilities do not occur for stiff polymer solutions. The flow of flexible polymers is strongly perturbed even far from the region of instability, and this phenomenon can be used to produce mixing*.

*Phys. Rev. Letters, 96, 144502 (2006)

This work was supported primarily by NSF DMR-0405187, with additional support by NSF DMR05-20020.