Menu

Discussion Forum

New Discussion
Filter

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Continuous delivery in transport and surface reaction model

Posted May 29, 2012, 4:36 p.m. EDT Fluid & Heat, Microfluidics, Chemical Reaction Engineering Version 4.2 5 Replies

Bozhi Ji
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi all,

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.
5 Replies Last Post Aug 21, 2012, 7:51 a.m. EDT
Bozhi Ji
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago May 30, 2012, 10:41 a.m. EDT
Can anybody help me on this??
Can anybody help me on this??
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago May 31, 2012, 2:03 a.m. EDT
Hi

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

--
Good luck
Ivar
Hi 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 -- Good luck Ivar
Bozhi Ji
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Jun 3, 2012, 6:26 a.m. EDT
thank you very much. I am trying to do this with your suggestions.

thank you very much. I am trying to do this with your suggestions.
Mayur
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Jul 24, 2012, 9:52 a.m. EDT
why u have symmetry in all directions..
why u have symmetry in all directions..
Bozhi Ji
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Aug 21, 2012, 7:51 a.m. EDT
Thank you for your suggestions, I have changed the settings, but the flow concentration profile still seams not good for me so far. So have you got any further suggestions?
Thank you for your suggestions, I have changed the settings, but the flow concentration profile still seams not good for me so far. So have you got any further suggestions?

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content