TAYLOR,wid,vel,dcoef,sel
Taylor dispersion in microfluidic channels

wid         channel width [µm]
vel          fluid velocity in the channel [mm/s]
dcoef      diffusion coefficient of solute [m2/s]
sel          number denoting the selected result.
               Use 2 for dispersion coefficient

Notes

Taylor dispersion deals with the distribution of solute molecules in a solvent that is moving with a fixed velocity in a microchannel. Immediately after the introduction of the dye, the dye molecules are stretched in a straining field and aligns itself in a band parallel with the axis of flow. As time passes, diffusion starts to take effect and evens out the distribution over the width of the channel. The result is that the dye molecules spread out in the direction of flow much faster than if molecular diffusion was the only mechanism. This phenomenon is often used in many micromixers.

Due to dispersion, the diffusion coefficient increases. The effective diffusion coefficient depends on a few parameters like the shape of the channel, the fluid velocity, the transverse dimension of the canal and the diffusion coefficient of the solute molecules.  This design form can be used to estimate the effective diffusion coefficient or dispersion coefficient as it is sometimes called for channels with different cross-sectional shape.

The plot shows the Taylor dispersion coefficient as a function of molecular diffusion coefficient. It shows that when diffusion coefficient is small, dispersion is more pronounced.

Assumptions

-The velocity field of the solvent is not zero.
-Convection dominates diffusion.
 
Menu Path

Mechanics > Fluidics > Diffusion > Spreading > Moving fluid


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