Please use this identifier to cite or link to this item: https://hdl.handle.net/10216/106699
Author(s): M. S. N. Oliveira
F. T. Pinho
M. A. Alves
Title: Divergent streamlines and free vortices in Newtonian fluid flows in microfluidic flow-focusing devices
Issue Date: 2012
Abstract: 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.
Subject: Engenharia mecânica
Mechanical engineering
Scientific areas: Ciências da engenharia e tecnologias::Engenharia mecânica
Engineering and technology::Mechanical engineering
URI: https://repositorio-aberto.up.pt/handle/10216/106699
Related Information: info:eu-repo/grantAgreement/FCT - Fundação para a Ciência e Tecnologia/Projectos de I&DT em Todos os Domínios Científicos/PTDC/EME-MFE/099109/2008/ANEURYSM - Estudo Hemodinâmico em Aneurismas Cerebrais/ANEURYSM
info:eu-repo/grantAgreement/FCT - Fundação para a Ciência e Tecnologia/Projectos de I&DT em Todos os Domínios Científicos/PTDC/EQU-FTT/118716/2010/Design de um "reómetro-num-chip" para o desenvolvimento de fluidos análogos ao sangue/RheoChip
info:eu-repo/grantAgreement/FCT - Fundação para a Ciência e Tecnologia/Projectos de I&DT em Todos os Domínios Científicos/PTDC/EME-MFE/114322/2009/EXTENSION - Escoamento extensional de fluidos complexos em microcanais/EXTENSION
Document Type: Artigo em Revista Científica Internacional
Rights: restrictedAccess
Appears in Collections:FEUP - Artigo em Revista Científica Internacional

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