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The Diffusion of Passive Tracers in Laminar Shear Flow
Published on: May 1, 2018
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Diffusioosmotic flow in rectangular microchannels.
Vahid Hoshyargar1, Seyed Nezameddin Ashrafizadeh1, Arman Sadeghi2
1Research Lab for Advanced Separation Processes, Department of Chemical Engineering, Iran University of Science and Technology, Narmak, Tehran, Iran.
Electrophoresis
|March 21, 2016
Summary
This study explores diffusioosmosis in rectangular channels, finding flow patterns depend on the width-to-height ratio. This reveals a new control mechanism for diffusioosmotic flow in microchannels.
Area of Science:
- Fluid dynamics
- Electrochemistry
- Microfluidics
Background:
- Diffusioosmosis is the movement of electrolyte solutions in charged channels.
- Microchannel geometry significantly impacts fluid behavior.
- Modeling rectangular channels as slits can introduce errors.
Purpose of the Study:
- To quantify errors from modeling rectangular microchannels as slits.
- To investigate the influence of channel aspect ratio on diffusioosmosis.
- To identify new methods for controlling diffusioosmotic flow.
Main Methods:
- Finite element numerical analysis.
- Simulation of electrolyte solution flow in uniformly charged rectangular channels.
- Analysis of flow patterns and mean velocity based on channel aspect ratio.
Main Results:
- Flow pattern and direction are dependent on the channel's width-to-height ratio.
- Mean velocity increases with aspect ratio up to a certain point, then plateaus.
- A slip-like velocity, analogous to Helmholtz-Smoluchowski velocity, is observed and modeled.
Conclusions:
- Slit geometry is inadequate for accurately representing rectangular microchannels with small aspect ratios.
- Channel aspect ratio offers a mechanism for controlling diffusioosmotic flow.
- The derived slip velocity expression is crucial for microchannel applications.
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