Dispersion enhancement and damping by buoyancy driven flows in 2D networks of capillaries

TL;DR

This study investigates how buoyancy-driven flows influence dispersion and damping in 2D microchannel networks, revealing the effects of density differences and flow velocity on fluid displacement and mixing.

Contribution

It introduces an experimental analysis of buoyancy effects on miscible fluid displacement in 2D networks and proposes a model applicable to 3D media.

Findings

Dispersion coefficient depends on flow velocity and buoyancy effects.

Stable and unstable displacement regimes are characterized.

A model links buoyancy-driven flow to dispersion behavior.

Abstract

The influence of a small relative density difference on the displacement of two miscible liquids is studied experimentally in transparent 2D networks of micro channels. Both stable displacements in which the denser fluid enters at the bottom of the cell and displaces the lighter one and unstable displacements in which the lighter fluid is injected at the bottom and displaces the denser one are realized. Except at the lowest mean flow velocity U, the average $C(x,t)$ of the relative concentration satisfies a convection-dispersion equation. The dispersion coefficient is studied as function of the relative magnitude of fluid velocity and of the velocity of buoyancy driven fluid motion. A model is suggested and its applicability to previous results obtained in 3D media is discussed.