# How to use non-uniform boundary condition

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 November 2, 2012, 02:26 How to use non-uniform boundary condition #1 New Member   j.t. Join Date: Nov 2012 Posts: 11 Rep Power: 6 Sponsored Links 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 ; { ..... ..... } 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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 November 12, 2012, 10:27 #2 Member   Duong A. Hoang Join Date: Apr 2009 Location: Delft, Netherlands Posts: 93 Rep Power: 10 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

 November 12, 2012, 13:45 #3 Senior Member     Daniel P. Combest Join Date: Mar 2009 Location: St. Louis, USA Posts: 612 Rep Power: 22 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. __________________ Dan Find me on twitter @dancombest and LinkedIn

 December 18, 2012, 17:59 #4 New Member   j.t. Join Date: Nov 2012 Posts: 11 Rep Power: 6 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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