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how to write????

Posted Nov 3, 2013, 9:14 a.m. EST Version 4.2 7 Replies

Anup Paul
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Dear friend

Can anyone help me to write the following equation in comsol

dX/dt=(A)*[exp{-E/RT}]


where

A, E & R=constant

T=variable

want to solve to find out X.............


rgds


Anup
7 Replies Last Post Nov 8, 2013, 8:11 a.m. EST
Pietro Pollaci
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Posted: 1 decade ago Nov 3, 2013, 10:23 a.m. EST
I'm confused, are t on lhs and T on rhs the same variable?
Or t is time and T = T(t) is temperature as function of time?

Cheers
I'm confused, are t on lhs and T on rhs the same variable? Or t is time and T = T(t) is temperature as function of time? Cheers
Anup Paul
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Posted: 1 decade ago Nov 4, 2013, 1:40 a.m. EST
hi Pollaci,

here

T is temperature, which is function of time as well as space

t-time


rgds

Anup

hi Pollaci, here T is temperature, which is function of time as well as space t-time rgds Anup
Jens Krause
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Posted: 1 decade ago Nov 4, 2013, 2:56 a.m. EST
Your create a "dode" that is physics of type
Domain ODEs and DAEs

Then in "Distributed ODE 1"

you enter :

da=1
ea=1
f= (A)*[exp{-E/RT}]

That shou do the jo

Regards,

Jens
Your create a "dode" that is physics of type Domain ODEs and DAEs Then in "Distributed ODE 1" you enter : da=1 ea=1 f= (A)*[exp{-E/RT}] That shou do the jo Regards, Jens
Anup Paul
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Posted: 1 decade ago Nov 4, 2013, 6:43 a.m. EST
thanks
thanks
Anup Paul
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Posted: 1 decade ago Nov 4, 2013, 7:00 a.m. EST
Dear Jens

I think "ea" should be zero, otherwise it will become 2nd order ODE.


rgds


Anup
Dear Jens I think "ea" should be zero, otherwise it will become 2nd order ODE. rgds Anup
Jens Krause
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Posted: 1 decade ago Nov 4, 2013, 8:56 a.m. EST
yes, that is a typo, Jens
yes, that is a typo, Jens
Anup Paul
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Posted: 1 decade ago Nov 8, 2013, 8:11 a.m. EST
Hi

I got a problem here, as i have mentioned, equation contains three variable:

1. time 't'
2. Temperature 'T'
3. Variable 'X ' which is again a function of three space coordinate and time ???
* All other parameters are constant

The temperature T is obtained after solving a "Transient heat diffusion equation in solid Physics" and is used as the input to the ODE. That means the two physics "Transient heat diffusion equation in solid Physics" AND "Distributed ODEs and DAEs(dode) Physics" should be coupled together since I need the value of T(x,y,z,t) to calculate X (x, y,z,t).


Can anyone please tell me, how to couple these two physics in COMSOL 4.2??


regards


Anup
Hi I got a problem here, as i have mentioned, equation contains three variable: 1. time 't' 2. Temperature 'T' 3. Variable 'X ' which is again a function of three space coordinate and time ??? * All other parameters are constant The temperature T is obtained after solving a "Transient heat diffusion equation in solid Physics" and is used as the input to the ODE. That means the two physics "Transient heat diffusion equation in solid Physics" AND "Distributed ODEs and DAEs(dode) Physics" should be coupled together since I need the value of T(x,y,z,t) to calculate X (x, y,z,t). Can anyone please tell me, how to couple these two physics in COMSOL 4.2?? regards Anup

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