Menu

Discussion Forum

New Discussion
Filtrer

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.

Transport of dilute species module

Posted 9 févr. 2015, 03:42 UTC−5 6 Replies

Jayarama Krishna J V
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi,
Plz help me out to know how to enter nonlinear rate expressions bcz comsol is not taking powers like 0.5 i.e c*c2^0.5.
I kindly request anyone of them to give a reply soon.
Thanx a lot..
6 Replies Last Post 9 févr. 2015, 06:14 UTC−5
Lasse Murtomäki
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 9 févr. 2015, 04:21 UTC−5
Hi

Attached my solution to the problem; c is the variable. I used the flux condition

-k*C0*(c/C0)^a

where k is the heterogeneous rate constant (cm/s). You must use the scaling concentration C0 = 1 mol/L in the non-linear condition, because the units do not agree otherwise. Now, (c/C0)^a is dimensionless number. In order to make the flux in mol/(cm²·s), I multiply the expression again with C0, which makes the units correct. Basically, it is just question of dividing and multiplying with 1, but you must adjust the value of k to make the physical situation coincide with your experiments.

best regards
Lasse
Hi Attached my solution to the problem; c is the variable. I used the flux condition -k*C0*(c/C0)^a where k is the heterogeneous rate constant (cm/s). You must use the scaling concentration C0 = 1 mol/L in the non-linear condition, because the units do not agree otherwise. Now, (c/C0)^a is dimensionless number. In order to make the flux in mol/(cm²·s), I multiply the expression again with C0, which makes the units correct. Basically, it is just question of dividing and multiplying with 1, but you must adjust the value of k to make the physical situation coincide with your experiments. best regards Lasse

Attachments:

Jayarama Krishna J V
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 9 févr. 2015, 05:12 UTC−5
thanx sir but i am using 4.4 licensed version of comsol,so the .mph is not opening.When i tried to replace c2 by c2/C0 it is showing error telling dat C0 is unknown variable.
Regards
thanx sir but i am using 4.4 licensed version of comsol,so the .mph is not opening.When i tried to replace c2 by c2/C0 it is showing error telling dat C0 is unknown variable. Regards
Lasse Murtomäki
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 9 févr. 2015, 05:13 UTC−5
You have to define C0, a and k in the global parameters list.
You have to define C0, a and k in the global parameters list.
Jayarama Krishna J V
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 9 févr. 2015, 05:43 UTC−5
Respected Sir,
The following is the expression i wish to enter in the flux condition of transport of dilute species module.Plz let me know as where am i going wrong as comsol is showing error.
-0.476[mol^0.5/s*m^0.5]*(c[mol/m^3]*(c2[mol/m^3])^0.5)/(1+998*c[mol/m^3])
I will be extremely thankful to you
Regards
Respected Sir, The following is the expression i wish to enter in the flux condition of transport of dilute species module.Plz let me know as where am i going wrong as comsol is showing error. -0.476[mol^0.5/s*m^0.5]*(c[mol/m^3]*(c2[mol/m^3])^0.5)/(1+998*c[mol/m^3]) I will be extremely thankful to you Regards
Jayarama Krishna J V
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 9 févr. 2015, 05:52 UTC−5
Thank you sir.I will definitely try by defining them in the global parameter list
Thank you sir.I will definitely try by defining them in the global parameter list
Lasse Murtomäki
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 9 years ago 9 févr. 2015, 06:14 UTC−5
Hi

What is that 998 in the denominator? Water density in kg/m^3? Anyway, I would write

-k*c*(c2/C0)^a/(1+K*(c/C0))

k = 0.476[m/s] (or whatever you need)
C0 = 1[mol/l]
a = any number
K = 998 (no unit)

Now the flux has unit mol/(m²·s) since c has the unit mol/m^3.

br
Lasse
Hi What is that 998 in the denominator? Water density in kg/m^3? Anyway, I would write -k*c*(c2/C0)^a/(1+K*(c/C0)) k = 0.476[m/s] (or whatever you need) C0 = 1[mol/l] a = any number K = 998 (no unit) Now the flux has unit mol/(m²·s) since c has the unit mol/m^3. br 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