Purely elastic turbulence in pressure-driven channel flows

Area of Science:

• Fluid dynamics
• Polymer physics
• Complex fluids

Background:

• Solutions of long, flexible polymer molecules exhibit complex fluid and solid-like properties.
• Dilute polymer solutions display elastic turbulence, a chaotic flow state unique to non-Newtonian fluids, occurring at low inertia.
• The underlying mechanism of elastic turbulence remains poorly understood despite experimental documentation.

Purpose of the Study:

• To investigate the mechanism of elastic turbulence using large-scale direct numerical simulations.
• To analyze the transition to elastic turbulence in pressure-driven channel flows.
• To identify the organizational structures underlying elastic turbulence.

Main Methods:

• Large-scale direct numerical simulations (DNS) were employed.
• The study focused on pressure-driven flows of polymer solutions through straight channels.
• Analysis involved examining flow structures and their evolution.

Main Results:

• The transition to elastic turbulence was found to be sub-critical.
• Initial spot-like flow structures were observed, which later expanded across the domain.
• Elastic turbulence is organized around unstable coherent states localized near the channel midplane.

Conclusions:

• Direct numerical simulations provide insights into the mechanism of elastic turbulence.
• The sub-critical nature and localized structures offer a new perspective on elastic turbulence onset.
• Understanding these organized states is crucial for controlling complex fluid flows.