Title: Flow and transport in a 2D wavy channel of randomly varying aperture
Author: Gianluca Boccardo
Our work deals with the investigation of fluid flow and solute transport in channels of randomly varying apertures: the study of this problem is relevant to many direct practical applications in systems both natural, as fractured geological formations, and engineered, as microfluidics devices.
The existing works dealing with transport in channels with non-constant diameter are limited to periodically varying apertures or small-scale roughness in pipes: the available literature indicates non-trivial effects on apparent mechanical dispersion resulting from variations in channel apertures, but a full description of the problem considering the range of variation of the geometrical features of realistic systems is still missing.
The aim of the current study is thus to improve on the current understanding of these effects, specifically by studying the influence of randomness in the channel size.
In our approach, we build a suitable number of geometric realizations of 2D channels with sinusoidally varying apertures of random amplitude and random channel diameter. Then, flow field and particle transport are investigated by means of finite volume CFD simulations (using the open-source code OpenFOAM).
First, flow field is obtained in Stokes regime, then the solute transport is studied via Lagrangian particle tracking, covering a very wide range of Péclet numbers.
Values of permeability are calculated and related to variations in sinusoidal amplitude and channel diameter.
Finally, values of solute dispersion are presented against variations in channel geometry.
We observe marked differences compared with the classical Taylor-Aris solution for transport in pipes and the mentioned study on periodic channels: as such, the results of this work highlight the great impact of geometric configuration on both flow and transport.