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Pressure Outlet - Effect of domain

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Old   March 24, 2016, 05:20
Default Pressure Outlet - Effect of domain
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Bineet Mehra
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Hello

I am modeling a conjugate heat transfer problem in STARCCM.
Inlet - Velocity Inlet
Outlet - Pressure Outlet

Flow - Laminar, Low R, Steady

As i change the distance between the trailing edge of the fin and outlet, P-inlet keeps on changing. I started with very small distance between Trailing edge of fin and outlet and then kept on increasing it. I did 6 simulations with different distance between Trailing edge of fin and outlet. I expect constant P at inlet after some value of this distance between Trailing edge of fin and outlet but its not the case. Aim is to get pressure drop. The lateral boundaries around outlet are symmetry planes. There is no recirculation at the outlet.

Any Suggestion ? Help

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Old   March 24, 2016, 16:37
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Matt
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Generally speaking, you should always place your boundary conditions far enough away that they do not impact your measurement. When you say that you did 6 sims and never saw this value flatten out, are you sure that you ever got 'far enough' away?

There are some exceptions to this rue and without seeing your geometry I can only speculate, but my guess is what you feel is far enough in reality is too close.
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Old   March 30, 2016, 06:30
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Quote:
Originally Posted by MBdonCFD View Post
Generally speaking, you should always place your boundary conditions far enough away that they do not impact your measurement. When you say that you did 6 sims and never saw this value flatten out, are you sure that you ever got 'far enough' away?

There are some exceptions to this rue and without seeing your geometry I can only speculate, but my guess is what you feel is far enough in reality is too close.
Thanks MBdonCFD for the information. I shall do some simulations with increased domain length for the outlet section. Will let you know.

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Old   April 5, 2016, 05:51
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Bineet Mehra
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The distance from Trailing edge of the fin and the outlet section was not enough. P at inlet not changing now for distance between TE of fin and outlet section more than 4L, L is the length if the fin.

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