Dynamics and fragmentation of small inextensible fibers in turbulence

TL;DR

This study investigates how small inextensible fibers break in turbulence through tensile and buckling failures, using detailed simulations to develop models predicting fiber size evolution based on flow-induced stresses.

Contribution

It introduces a comprehensive simulation-based analysis of fiber fragmentation in turbulence, linking breakup statistics to fluid velocity gradients and fiber flexibility.

Findings

Fragmentation rate depends on local flow conditions.

Buckling and tensile failures are key breakup mechanisms.

Statistics are governed by fluid velocity gradient distributions.

Abstract

The fragmentation of small, brittle, flexible, inextensible fibers is investigated in a fully-developed, homogeneous, isotropic turbulent flow. Such small fibers spend most of their time fully stretched and their dynamics follows that of stiff rods. They can then break through tensile failure, i.e. when the tension is higher than a given threshold. Fibers bend when experiencing a strong compression. During these rare and intermittent buckling events, they can break under flexural failure, i.e. when the curvature exceeds a threshold. Fine-scale massive simulations of both the fluid flow and the fiber dynamics are performed to provide statistics on these two fragmentation processes. This gives ingredients for the development of accurate macroscopic models, namely the fragmentation rate and daughter-size distributions, which can be used to predict the time evolution of the fiber size distribution. Evidence is provided for the generic nature of turbulent fragmentation and of the resulting population dynamics. It is indeed shown that the statistics of breakup is fully determined by the probability distribution of Lagrangian fluid velocity gradients. This approach singles out that the only relevant dimensionless parameter is a local flexibility which balances flow stretching to the fiber elastic forces.