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Old   July 26, 2012, 01:40
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hi
I am beginner in fluent. I have a problem that have a convective B.C in outlet as follows:
000.png


that is a independent variable p,v and T.
can anyone help me for this case??
thanks ..
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Old   July 26, 2012, 01:42
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sorry . the equation is :

000.png
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Old   July 26, 2012, 02:42
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Dear friend,

you can consider phi as a scalar and solve a modified UDS equation for that easily and set a Dirichlet BC instead, but I think you meant that phi is a dependent variable.

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Old   July 26, 2012, 04:19
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thanks amir
but phi is a independent variable. but i dont know that what to do and begin from which step?
this is the problem of channel that air passes through it.
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Old   July 26, 2012, 04:22
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Quote:
Originally Posted by eh65 View Post
thanks amir
but phi is a independent variable. but i dont know that what to do and begin from which step?
this is the problem of channel that air passes through it.
What's the governing equations and what is phi variable?!
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Old   July 26, 2012, 04:41
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(d/dt)(phi)+ U(d/dx)(phi)= 0
phi is pressure, tempreture and avreaged x-velocity (U)
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Old   July 26, 2012, 04:51
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Quote:
Originally Posted by eh65 View Post
(d/dt)(phi)+ U(d/dx)(phi)= 0
phi is pressure, tempreture and avreaged x-velocity (U)
Ah, sorry I think this is sth different at first. Ok, here note that for some BCs you cannot set both velocity and pressure. But you have 2 choices:
1) using a separate UDS equation but it may face some difficulties in its own BCs
2) write a UDF like this:
phi_new=phi_old-U(d/dx phi)*dt
which is a approximation.

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Old   July 26, 2012, 05:04
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thanks
in situation 2 i have to use flux uds?
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Old   July 26, 2012, 05:17
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Quote:
Originally Posted by eh65 View Post
thanks
in situation 2 i have to use flux uds?
No! in this situation you wouldn't need any UDS. you're setting phi directly. (note that you can access gradient operator in UDF)
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Old   July 26, 2012, 11:57
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thanks amir
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