Dynamically forced cells of a viscoelastic fluid over an array of rollers

TL;DR

This study investigates the behavior of viscoelastic fluids over rotating rollers, revealing cell formation, oscillations, and complex dynamics influenced by fluid relaxation time, with implications for understanding fluid elasticity effects.

Contribution

It demonstrates how viscoelastic fluid cells form and oscillate over rollers, highlighting the transition from Newtonian-like to elasticity-dominated flow regimes based on relaxation time.

Findings

Cells form with convex surfaces above rollers at long relaxation times

Fluid oscillations become irregular with multiple frequencies as relaxation time increases

Flow transitions from Newtonian-like to elasticity-driven dynamics

Abstract

Our fluid dynamics video shows the response of a layer of viscoelastic fluid to an array of four-roll mills steadily rotating underneath. When the relaxation time of the fluid is sufficiently long, the fluid divides into "cells" with a convex free surface above the site of each roller. This is reminiscent of the rod-climbing effect. On this relaxation time-scale, the flow also transitions from being initially Newtonian-like to one where the fluids' elasticity plays a dynamical role: The fluid cells oscillate with regularity in position and shape on a timescale much longer than the relaxation time. As the relaxation time is further increased, the cells become less localized to the underlying rollers, and their now irregular oscillations reflect the presence of many frequencies.