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Old   July 22, 2014, 13:09
Default Simple Fluid Mixing
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I apologize if this is a basic question, but I am trying to model the mixing of 4 reagents with properties identical to water in a microfluidic device. I have tried making individual materials and assigning each a phase in the multiphase mixing model, but the model ended up being incorrect. I could not find a relevant tutorial, anyone have any advice or a tutorial they could refer me to?
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Old   July 22, 2014, 13:13
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Could you upload the geometry and specify the inlets and outlet on it ?
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Old   July 22, 2014, 13:22
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No, unfortunately I really cant. I have 4 pressure inlets, and one pressure outlet. I simply want to have different species enter at each inlet. Is there any simple way to do that?
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Old   July 22, 2014, 13:31
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First u need to use multiphase model . And assign a
Volume fraction 1 for for each inlet and at outlet calculate the volume fraction for each phase . In material u need to add four materials
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Old   July 22, 2014, 14:22
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I fail to understand why would you use multiphase model. If all reagents have the same properties and are in the same phase, you could model the problem using species transport model.
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Old   July 22, 2014, 14:30
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What fluids are you going to use ?
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Old   July 22, 2014, 15:01
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Until recently, I couldn't figure out how to add custom species to species transport model, I just figured out how to edit the mixture template to include my custom materials. I assume species transport will work better, Ill try and model this one now. Is there documentation on this? I couldnt seem to find it. As far as the fluid, water can be used to approximate each reagent.
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Old   July 22, 2014, 16:11
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still having trouble, anyone know where i could find an example like this in documentation?
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Old   July 22, 2014, 16:56
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The way I would go about it would be to select an appropriate mixture template. It may be one that has the same number of species that you want to model. Then you can edit each of the species properties to set them equal to water and equal to each other. You can even edit the names and change them to water-1, water-2, etc. Make sure you appropriately define the diffusion coefficient, since it will play an important role on your mixing calculations.
I guess that in you have at least 4 inlet for your domain. Set the species mass fraction or mole fraction for each of the correspondent specie on each inlet. If each inlet is 100% one specie, it would be something like: inlet-1, mass fraction of water-1=1.0, and so on.
Your discretization schemes and mesh size will influence your results. It would be pertinent to try different mesh sizes in order to establish the influence of numerical diffusion. Selecting higher order monotonic schemes should reduce the amount of numerical diffusion.
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