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Abstract:
This paper presents numerical and experimental analysis of the hydrodynamic flow focusing in a rectangular microchannel. Aim of the study is to improve performance of the Particle Image Velocimetry (PIV) technique app lied to micro-scale flow analysis. The symmetric flow focusing system of two channels crossed at right angle is investigated. The numerical model is used to analyse the e ffect of Reynolds number on the flow focusing mechanism. In the experiment, the flow foc using is applied to concentrate seeding tracers into a thin sheet at the channel axis. Such a modification removes the out of focus images of the seeding particles, effe ctively improving PIV evaluation of vector fields in microchannel. Based on the exp erimental and numerical results we have found that expected improvement is possible for the flow at Reynolds number less than 10 only.

Keywords:
selective seeding, flow focusing

Abstract:
This paper presents numerical analysis of the hydrodynamic flow focusing in rectangular microchannels. The low Reynolds numer pressure driven flow in symmetric system of crossed channels with three inlets and one outlet is investigated. The numerical model is used to elucidate the origin of broadening of the focused flow sheet observed experimentally close to the side walls of the outlet channel. It is found that the observed broadening is mainly due to the residual flow inertia and can be totally eliminated if flow Reynolds number is less than one.