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how to make my variable changes with time??
Posted 21 ott 2011, 10:39 GMT-4 Heat Transfer & Phase Change Version 4.2 2 Replies
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Hello all,
I am new user of COMSOL-Heat transfer module.
I want to make my heat source (heat flux) is function of time...
Example:
Q (heat flux)= 200/5 * t1
hear t1 is time which is selective like (0, 5, 10, 15 second).... So my heat source supply heat when t1==t (actual time)..
Please help me in this matter, I tried analytical but I think, I could not understand this function properly !!!
Thanks in advance. :)
Regards,
Chirag Patel
2 Replies Last Post 22 ott 2011, 11:20 GMT-4
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Posted:
1 decade ago
Hi
if you want a wariable to change with time, you simply write out the equation with the internal variable "t" such as
Q = Qa[W/m^2/s] * t + Q0[W/m^2]
the units might change depending on your model and BC conditions.
If you want to "turn on and/or off" a source at a given time or during a period of time, then define a "step()", or "pulse" operator to add in the "Definition - Function" node and multiply the Qa by this step function, i.e.
Q = Qa[W/m^2] * step(t[1s]) + Q0[W/m^2]
Note the change of units, AND the t[1/s] as operators/functions want that the call variables are unitless, in this case I enforce it to seconds, but min or hours are also possible (check the units symbols in the doc)
To begin with COMSOL you need to read the doc a few times to get used to the notations, it takes some time, but it's fully worth it
--
Good luck
Ivar
if you want a wariable to change with time, you simply write out the equation with the internal variable "t" such as
Q = Qa[W/m^2/s] * t + Q0[W/m^2]
the units might change depending on your model and BC conditions.
If you want to "turn on and/or off" a source at a given time or during a period of time, then define a "step()", or "pulse" operator to add in the "Definition - Function" node and multiply the Qa by this step function, i.e.
Q = Qa[W/m^2] * step(t[1s]) + Q0[W/m^2]
Note the change of units, AND the t[1/s] as operators/functions want that the call variables are unitless, in this case I enforce it to seconds, but min or hours are also possible (check the units symbols in the doc)
To begin with COMSOL you need to read the doc a few times to get used to the notations, it takes some time, but it's fully worth it
--
Good luck
Ivar
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Posted:
1 decade ago
Hi, Ivar
Thank you very much for your reply.