Date of Award

2011

Degree Type

Thesis

Department

Mechanical Engineering

First Advisor

Ibrahim, Mounir

Subject Headings

Microfluidics, Biotechnology, microfluidics, microflow, micromixer, passive mixer, dean flow, microchannel flow

Abstract

The DNA Medicine Institute (DMI) is currently developing a device to be used for blood analysis to satisfy the unique requirements of space medicine applications. A key component of that device is the micromixer, which will ensure mixing and dilution of reagents utilized for detection assays. As part of the device design process, the micromixer was modeled, and the mixing characteristics were analyzed and compared to experimental data. The experimental data was based on a top-view of the system and, lacking data throughout the fluid domain, could not provide the insight into the mixing process that modeling could readily provide. COMSOL, a Finite Element Method (FEM) package, was used to model the mixer. The mixer design is essentially a spiral channel and relies on centrifugal effects, or Dean flow forces that arise from flows in curved channels, to enhance mixing. A computational model of DMI's spiral mixer was analyzed and compared to experimental data for flow ranging in Reynolds number between 8 and 90. The Dean number range was between 0 and 25. The fluids modeled were miscible and Newtonian. It was observed that at Reynolds number less than 12 (De 11), convective forces dominated. In an intermediate range, Reynolds numbers between 12 and 30 (De 2 - 11), mixing appeared to be enhanced as both diffusion and convection aided the mixing. Due to the rotational nature of the flow, this was not readily apparent from the experimental data. The model is a good tool to optimize design choices since the numerical data can be used to quantify mixing characteristics throughout the entire mixer volume, thereby providing a better insight into mixing performance

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