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BC for heat flux
Posted 9 sept. 2010, 17:33 UTC−4 3 Replies
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Hello,
I´m trying to simulate le heat flux through a wall but I have the heat flux like a boundary condition and it change with the time. The problem is from a text book because i'm learning how to use the boundary condition variying with time.
I have the diferents values of Q for the 24 hours the day. It change every 3 hours but my simulations have a period of time in seconds like (0, 10, 900). The runs are every 15 minutes. I actually use the stored solutions options to take the last value like inicial value for the next run.
I found 2 ways to input the heat flux variying in time:
1) Put the values in a table in the options - fuctions - new - interpolate - table, but put the values of Q from 0 to 900 seconds
Can I enter a range of time for avoiding enter the same data every 3 hours?
2) the other way is enter a function that discribes the change of Q through the day.
If I put the data for all day from 0 seg to 86400 seg.. does COMSOL will only take the first 900 seconds for my range of times: range(0,100,900) ?
Thank you, in advance...
Ivette
I´m trying to simulate le heat flux through a wall but I have the heat flux like a boundary condition and it change with the time. The problem is from a text book because i'm learning how to use the boundary condition variying with time.
I have the diferents values of Q for the 24 hours the day. It change every 3 hours but my simulations have a period of time in seconds like (0, 10, 900). The runs are every 15 minutes. I actually use the stored solutions options to take the last value like inicial value for the next run.
I found 2 ways to input the heat flux variying in time:
1) Put the values in a table in the options - fuctions - new - interpolate - table, but put the values of Q from 0 to 900 seconds
Can I enter a range of time for avoiding enter the same data every 3 hours?
2) the other way is enter a function that discribes the change of Q through the day.
If I put the data for all day from 0 seg to 86400 seg.. does COMSOL will only take the first 900 seconds for my range of times: range(0,100,900) ?
Thank you, in advance...
Ivette
3 Replies Last Post 10 sept. 2010, 04:22 UTC−4
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Posted:
1 decade ago
Someone help me please !!! =(
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Posted:
1 decade ago
Hi Ivette,
so if you defined your BC as tables or functions you have done everthing all right. I think the problem is, that you have choosen "time steps taken from solver" as "Free". So if COMSOL takes time steps, which a too big, COMSOL "jumps over" the changing BCs - since COMSOL does not really "know" where the steps of you BCs are. Do you have a 1D-problem? If yes, COMSOL should run really fast, so cou can set up low maximum time steps (e.g. delta t_max=20s or something like this).
In COMSOL you can choose "Periodic boundary conditions" - maybe this is something you can try -i never used it, and i don't really know what it exactly does - but it sounds quite interesting for you.
best regards
so if you defined your BC as tables or functions you have done everthing all right. I think the problem is, that you have choosen "time steps taken from solver" as "Free". So if COMSOL takes time steps, which a too big, COMSOL "jumps over" the changing BCs - since COMSOL does not really "know" where the steps of you BCs are. Do you have a 1D-problem? If yes, COMSOL should run really fast, so cou can set up low maximum time steps (e.g. delta t_max=20s or something like this).
In COMSOL you can choose "Periodic boundary conditions" - maybe this is something you can try -i never used it, and i don't really know what it exactly does - but it sounds quite interesting for you.
best regards
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Posted:
1 decade ago
Thank you so much...
Indeed I have problems with the time steep... I will check everything you said...
thank you. =)
Ivette.
Indeed I have problems with the time steep... I will check everything you said...
thank you. =)
Ivette.