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Fixed Flow rate and outlet Continuity Problem

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Old   March 9, 2012, 14:18
Default Fixed Flow rate and outlet Continuity Problem
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Mohammad.R.Shetab
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Dear Foamers,

I'm modeling a centrifugal fan in a fix flow rate with OF, but I had a problem and haven't find any solution for it!!!!

As I know in fluent it is modeled by these BCs:

inlet: massFlowRate

outlet: outflow

in OF I've tested many things like:

inlet: U: fixedFlowRate
p: fixedFluxPressure/zeroGradient

outlet: U: zeroGradient/fluxCorrectedVelocity
p: zerGradient

and a pRefCell and pRefValue for pressure reference. I think these Bcs are equivalent as the Fluent Bcs. When I run the MRFSimpleFoam the error would be

Continuity error cannot be removed by adjusting the outflow.
Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow.
Total flux : 56.788705
Specified mass inflow : 0.55
Specified mass outflow : 0
Adjustable mass outflow : 0

What is the problem? Thanks for your help.!!!
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Old   March 10, 2012, 14:32
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mauricio
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when you use a fixedflowrate type for bcs.. you cannot constraint the outlet else you'll get this error...enforcing zerograd on U does it..try using inletout types with massflow types.. cuz then u can have backflow

or convert your massflow to velocity and use, if possible :
inlet
Code:
u=fixedvalue
p=zerograd
outlet
Code:
u=zerograd
p=fixedvalue
see if it works
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