Divergent streamlines and free vortices in Newtonian fluid flows in microfluidic flow-focusing devices

• Type: Article in International Scientific Journal
• Date: 2012

Authors

M. S. N. Oliveira (Author) FEUP; F. T. Pinho (Author) FEUP; M. A. Alves (Author) FEUP

Journal

Title: Journal of Fluid Mechanics

Vol. 711 No. NOV 25 2012

Pages: 171-191

ISSN: 0022-1120

Publisher: Cambridge University Press

Indexing

ISI Web of Knowledge - 12 Citations

ISI Web of Science

Scopus - 19 Citations

Scientific classification

FOS: Engineering and technology > Mechanical engineering

Associated Projects

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RheoChip - Design de um "reómetro-num-chip" para o desenvolvimento de fluidos análogos ao sangue

EXTENSION - EXTENSION – Escoamento extensional de fluidos complexos em microcanais

Other information

Authenticus ID: P-002-3AH

DOI: 10.1017/jfm.2012.386

Abstract (EN): The appearance of divergent streamlines and subsequent formation of free vortices in Newtonian fluid flows through microfluidic flow-focusing geometries is discussed in this work. The micro-geometries are shaped like a cross-slot but comprise three entrances and one exit. The divergent flow and subsequent symmetric vortical structures arising near the centreline of the main inlet channel are promoted even under creeping flow conditions, and are observed experimentally and predicted numerically above a critical value of the ratio of inlet velocities (VR). As VR is further increased these free vortices continue to grow until a maximum size is reached due to geometrical constraints. The numerical calculations are in good agreement with the experimental observations and we probe numerically the effects of the geometric parameters and of inertia on the flow patterns. In particular, we observe that the appearance of the central recirculations depends non-monotonically on the relative width of the entrance branches and we show that inertia enhances the appearance of the free vortices. On the contrary, the presence of the walls in three-dimensional geometries has a stabilizing effect for low Reynolds numbers, delaying the onset of these secondary flows to higher V R. The linearity of the governing equations for creeping flow of Newtonian fluids was invoked to determine the flow field for any V R as a linear combination of the results of three other independent solutions in the same geometry.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 21