Menu

Discussion Forum

New Discussion
Filtrer

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 The information provided may be out of date.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.

Open Boundary Condition in Transport of Dilute Species

Posted 7 oct. 2015, 00:14 UTC−4 Fluid & Heat, Chemical Reaction Engineering Version 4.4 3 Replies

Edmund Lau
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi all,

I have a question about the open boundary in Transport of Dilute Species physics.

I have a microchannel model with fluid flow going from A to B while the solute going from B to A due to electric field. Looking at the equations in open boundary condition, it would seems the condition is only based on vector "u".

Question: Is the vector "u" resultant of both fluid flow (convection) and electrophoretic motion? or is it only the fluid flow (convection)? in other words, can the "open boundary" has inflow condition even though the fluid flow (convection) is flowing outward?

Thanks.
3 Replies Last Post 9 oct. 2015, 03:18 UTC−4
Lasse Murtomäki
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 8 oct. 2015, 01:41 UTC−4
Hi

In my understanding u is the convective velocity. Are you using Nernst-Planck equation?

BR
Lasse
Hi In my understanding u is the convective velocity. Are you using Nernst-Planck equation? BR Lasse
Edmund Lau
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 8 oct. 2015, 21:30 UTC−4
Hi Lasse,

Thanks for the reply, it would seems my result agrees with you. I am using the traditional convention-diffusion equation fyi.

But that raise a different question to the condition, shouldn't the switching condition for inflow/outflow depends on the resultant of convection, u, and electrophoretic velocity, u_ep (i.e. u+u_ep)? Thanks.

Edmund
Hi Lasse, Thanks for the reply, it would seems my result agrees with you. I am using the traditional convention-diffusion equation fyi. But that raise a different question to the condition, shouldn't the switching condition for inflow/outflow depends on the resultant of convection, u, and electrophoretic velocity, u_ep (i.e. u+u_ep)? Thanks. Edmund
Lasse Murtomäki
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 9 oct. 2015, 03:18 UTC−4
Hi

A very good question. Are yoy solving steady-state or time-dependent problem? I have to think of that...

Lasse

Hi A very good question. Are yoy solving steady-state or time-dependent problem? I have to think of that... Lasse

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