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Continuous delivery in transport and surface reaction model
Posted 29 mag 2012, 16:36 GMT-4 Fluid & Heat, Microfluidics, Chemical Reaction Engineering Version 4.2 5 Replies
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I am doing modelling with trasport and surface reaction in a flat micro-channel (L:W:H= 800um, 300um and 10um). In this model, one reaction solution is delivered into the channel in with laminar flow continuously. The reaction material will be adsorbed onto a square reaction spot (50um x 50um) in the botton of channel.
So I am modelling this with three physics, Transport of diluted species (chds), Laminar flow (spf) and Surface reaction (chsr) (shown in the attachment). After modelling, I have got some problems;
(1) As to my target, material is delivered continuously with constant initial concentration. But the result shows that the concentration from inlet varies all the time.
(2) The reaction spot (50um x 50 um) should be saturated with materials, but the results shows that it is changing all the time but never saturated even after long term.
Could anybody please help me on this? Any help and suggestion is massively appreciated.
Thank you.
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not evident what to say, from my side, chemistry is not ma everyday business
what puzzles me a bit is the velocity profile after the stationary study, you have a drastical slow up over your reaction patch, this is partially due to the no-slip condition building up there but not on the rest of the surface. Maybe you should remove the "symmetry condition on the lower wall which changes drastically the velocity profile.
Then remains the question about boundary mesh or not on the no-slip wall
suggestion: plot rather c/c0 than just c its easier to see the "oscillations"
You seem to have a wave of higher concentration flowing by, that takes > 10 seconds to pass, If I take the diffusivity D of 1000 [um^2/s] and your time stepping in seconds you have a delta_x of about 33um and a meshing of 30 um so the mesh is for me too rough but that's easily fixed, try the default physics induced mesh
Remains to find out if this rapid inrush and 50% concentration increas wave flowing by is physical or numerical. I'm not sure what to conclude there, but I would appreciate to hear from you if you observe it ;)
for me diffusion PDE equation could not make " stading waves" but here its a transient, if you solve for 30 sec it dies away
Interesting model anyhow
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Good luck
Ivar
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