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How to use non-uniform boundary condition

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Old   November 2, 2012, 02:26
Default How to use non-uniform boundary condition
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j.t.
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Hi all,

I need to specify an inlet velocity to the flow inlet (the case is a simple cuboid with flow entering the left and leaving the right side). I considered using the traditional inlet BC openfoam has, but I need to apply cyclic BCs for the inlet and outlet.And if I understand it right, the cyclic BC is applied as

inlet
{
type cyclic;
nFaces 256;
startFace 11520;
matchTolerance 0.0001;
neighbourPatch outlet;
}

outlet
{
type cyclic;
nFaces 256;
startFace 11776;
matchTolerance 0.0001;
neighbourPatch inlet;
}


There is no way I can specify the initial velocity (which is a constant 10 m/s throughout the inlet surface) to the inlet in the above definitions?


So is it that the only option I have is to specify the values of velocity at the inlet is to create a non-uniform field and assign individual velocity values throughout the domain in the form

internalField nonuniform <List>;
{
.....
.....
}

This approach is ok, but I have almost 5 million cells in my mesh and I really have no idea as to which cells correspond to the inlet.

Please guide me what to do here, since I am very new to openfoam..

Thanks in advance!
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Old   November 12, 2012, 10:27
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Duong A. Hoang
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Hi,

I do not think you can specify velocity with cyclic boundary condition. The driving force will be the pressure. So what you might want to do is to apply a pressure difference between the 'inlet' and 'outlet' of your domain. Then it will be fine, I think.

Duong
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Old   November 12, 2012, 13:45
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Daniel P. Combest
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Why not try the mapped patch instead of cyclic? This way you could define an inflow velocity. Otherwise, create or use a solver that has a way to drive the flow at a constant flow rate in a particular direction...like channelFoam.
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Old   December 18, 2012, 17:59
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j.t.
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Thank you all for replies. You are right, i cant apply velocity in periodic bc...and channelFoam looks apprppriate for me.
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