Polymer effects on Karman Vortex: Molecular Dynamics Study

TL;DR

This study uses molecular dynamics simulations to explore how polymers of different lengths influence the Karman vortex behind a circular cylinder, revealing significant effects of long polymers on vortex shedding and flow properties.

Contribution

It provides new insights into the molecular-level effects of polymers on vortex dynamics, highlighting the role of polymer extensibility in flow modification.

Findings

Long polymers reduce vortex shedding frequency.

Long polymers cause broadening of the lift coefficient spectrum.

Short polymers have minimal effect compared to Newtonian fluids.

Abstract

We investigated the Karman vortex behind a circular cylinder in a polymer solution by a molecular dynamics simulation. The vortex characteristics are distinctly different for short and long polymers. The solution with the long polymer exhibits a reduction in the vortex shedding frequency and broadening of the lift coefficient spectrum. On the other hand, the characteristics of the short-polymer solution are almost same as those of the Newtonian fluid. These facts are consistent with the experiments. Because the distributions of the gyration radius and the orientational order of the long-polymer solution are highly inhomogeneous in the flow field, we conclude that the extensional property of the polymer plays an important role in changing the flow characteristics.