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Old   March 24, 2009, 04:56
Default inlet boundary condition
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Jin Chen
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Hi all,

Is it possible to use mass flow rate as inlet boundary condition for incompreesilbe flow, the outlet is outflow.since i only have the information for mass flow rate for inlet,meanwhile the shape of inlet is kind of irregular,so i don't know the velocity profile or the average velocity for inlet.

By the way,when i choose this boundary parameter setting and starting simulation, the fisrt several steps occur reversed flow at outlet,could someone tell me why?

Any suggestions?

Regards
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Old   March 24, 2009, 06:22
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hi there

i can only tell ya massflowinlet is not necessary in the case of incompressable flow but you can use it anyway. once you know the mass, you know the q and you may know the v.




regards, buddy
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Old   March 24, 2009, 09:25
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I think you used the correct option. If the inlet shape is irregular, you cannot calculate the inlet velocity, so you can use the mass flow rate condition. Check the B.C whether the direction of inlet is specific or just 'normal to boundary'.

Reversed flow at outlet occurs initially due to convergence issues and also due to genuine back flow at the outlet. This may vanish once the solution converges. This should not be a problem. To completely avoid reversed flow, you may have to extend the geometry beyond the current outlet.
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Old   March 24, 2009, 10:38
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Thanks for your advices.

Now the simulation result seems ok with mass flow rate inlet and outlflow boudary settings.After few steps, the reversed flow vanished.
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Old   June 3, 2009, 16:58
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Gambit reports area of a surface when you pull the informations of it (the "i" icon)
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