Peripheral mixing of passive scalar at small Reynolds number

TL;DR

This paper investigates passive scalar mixing near walls at low Reynolds numbers using direct numerical simulations, confirming theoretical predictions and highlighting implications for microfluidics and environmental dispersion.

Contribution

It demonstrates the robustness of scalar mixing mechanisms near walls at low Reynolds numbers across different flow configurations, validating recent theoretical models.

Findings

Scalar concentration persists near walls due to identified mechanisms.

The phenomenology aligns with recent theoretical predictions.

Results have implications for microfluidic and environmental applications.

Abstract

Mixing of a passive scalar in the peripheral region close to a wall is investigated by means of accurate direct numerical simulations of both a three-dimensional Couette channel flow at low Reynolds numbers and a two-dimensional synthetic flow. In both cases, the resulting phenomenology can be understood in terms of the theory recently developed by Lebedev and Turitsyn [Phys. Rev. E 69, 036301, 2004]. Our results prove the robustness of the identified mechanisms responsible for the persistency of scalar concentration close to the wall with important consequences in completely different fields ranging from microfluidic applications to environmental dispersion modeling.