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Nadler, Michael E.

Mechanical Engineering

2010

MS

Laminar flow mixing remains an active area of research within the microfluidics community as it is a limiting factor to microchannel based systems requiring mixing of two or more fluids. Traditional mixing methods on the macro-scale often rely upon turbulent flow for mixing which is generally not present on the micro-scale and so alternative passive approaches must be sought. In this work we investigate the potential for enhanced laminar mixing due to the addition of inert, neutrally-buoyant particles of varying size and concentration in converging flows of miscible fluids at a 3-way microchannel 'Y' junction. It is hypothesized that particle migration resulting from combined hydrodynamic forces and particle interactions may passively mix fluids of differing mass species with an efficiency independent of flow rate; a characteristic similar to that of an typical active mixer.
By direct comparison with reference (non particle) experiments of the same Reynolds number, it is found that within experimental uncertainty, the addition of particulates to the flow offers. no measurable enhancement of laminar mixing over that which would normally occur due to mass diffusion processes alone. Thus the presence of particles in a microchannel flow offers neither a benefit nor an obstacle in microchannel mixing applications; indeed, the results of this work suggest that continuum analysis of the mixing process remain warranted, and therefore validates a continuum treatment of the fluids. This work has been partially supported by NASA under cooperative agreements NCC5-581 and NNG05GH16H.