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Old   January 19, 2005, 07:51
Default Mixing
Toni Vainio
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I am mixing 2 fluids (water and ethanol) in a y shaped micromixer. I have managed to build the model and add ethanol as a scalar, and process the flow. Then I use "getc (or Getv) conc 1 popt cont replot" to find the concentration of scalar (i.e. ethanol as I used water as my background fluid) However, I find that the contours shown are not what I predict. On the one hand when I plot the particle tracks I can see that the fluid does not mix quickly. But on the other the contour plots show that the scalar reaches 50 % of the mixture very quickly. Also it appears that the mixing occurs before the two fluids actually meet which intuitively is not what I would expect. Brian, as you have been answering my questions I am sure you would know what to do. Please send me your email and I can send you some pictures and method in a word document and maybe if you have time you can help answer my question. This is my final year project at university and without your help I probably wont be able to finish it. I am stuck.

Many thanks Toni

Many Thanks!
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Old   January 19, 2005, 08:21
Default Re: Mixing
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Particle tracks only show you convection. What about diffusion? Are the two scalars are diffusing into each other?
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Old   January 19, 2005, 08:31
Default Re: Mixing
Toni Vainio
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Oh, I didnt know that particle tracks only show convection. I am interesested in how fast the two liquids mix. I.e speed of diffusion. Yes both liquids should be diffusing into each other. I am using a square pipe: 100 micrometre*100 micrometre channel and inlet velocities of 0.033333 m/s. Flow should be laminar.

I also import the y shape from IDEAS in mm and before processing the flow I scale it down to 0.00001 to change the sacle of the geometry. Maybe this is adversely affecting my results?

In theory it should take 5.95 seconds (taken from a book) When I do it it takes 0.03 seconds to mix. I basically want to find a way to find how quickly the particles mix.

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