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Article Dans Une Revue Journal of Fluid Mechanics Année : 2021

Polymer scission in turbulent flows

Dario Vincenzi
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Takeshi Watanabe
Samriddhi Sankar Ray
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Jason R Picardo
Samriddhi Sankar Ray

Résumé

Polymers in a turbulent flow are subject to intense strain, which can cause their scission and thereby limit the experimental study and application of phenomena such as turbulent drag reduction and elastic turbulence. In this paper, we study polymer scission in homogeneous isotropic turbulence, through a combination of stochastic modelling, based on a Gaussian time-decorrelated random flow, and direct numerical simulations (DNS) with both one-way (passive) and two-way (active) coupling of the polymers, modelled as bead-spring chains, and the flow. For the first scission of passive polymers, the stochastic model yields analytical predictions which are found to be in good agreement with results from the DNS, for the temporal evolution of the fraction of unbroken polymers and the statistics of the survival of polymers. The impact of scission on the dynamics of a turbulent polymer solution is investigated through DNS with two-way coupling (active polymers). Our results indicate that the reduction of kinetic energy dissipation due to feedback from stretched polymers is an inherently transient effect, which is lost as the polymers break up. Thus, the overall dissipation reduction is maximized by an intermediate polymer relaxation time, for which polymers stretch significantly but without breaking too quickly. We also study the dynamics of the polymer fragments which form after scission; these daughter polymers can themselves undergo subsequent, repeated, breakups to produce a hierarchical population of polymers with a range of relaxation times and scission rates.
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Dates et versions

hal-03453906 , version 1 (28-11-2021)

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Dario Vincenzi, Takeshi Watanabe, Samriddhi Sankar Ray, Jason R Picardo, Samriddhi Sankar Ray. Polymer scission in turbulent flows. Journal of Fluid Mechanics, 2021, 912, ⟨10.1017/jfm.2020.1092⟩. ⟨hal-03453906⟩
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