# How do I prescribe Average Velocity /Total Inlet Flow for a simple channel problem?

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 November 29, 2013, 14:59 How do I prescribe Average Velocity /Total Inlet Flow for a simple channel problem? #1 Member   Sergey Join Date: Nov 2013 Posts: 86 Rep Power: 4 I'm trying to make a simple case - flow through a channel with no-slip BC at boundaries of the channel. I've prescribed fixedValue uniform velocity and zero gradient pressure at inlet. At outlet I've prescribed fixedValue pressure. (p=0) and zeroGradient velocity. I can run this case with these BC conditions, however velocity profile at inlet will be uniform and will not satisfy no-sleep BC and boundaries. Is any way to prescribe average velocity or total flow at inlet to satisfy zero BC for velocities? I was looking for the BC type here http://www.openfoam.org/docs/user/boundaries.php but was not able to fine average velocity or total flow type.

November 30, 2013, 08:15
#2
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Nima Samkhaniani
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i guess you have two options :

1- using flowRateInletVelocity
Quote:
 Example of the boundary condition specification for a volumetric flow rate: \verbatim myPatch { type flowRateInletVelocity; volumetricFlowRate 0.2; value uniform (0 0 0); // placeholder } \endverbatim Example of the boundary condition specification for a mass flow rate: \verbatim myPatch { type flowRateInletVelocity; massFlowRate 0.2; rho rho; rhoInlet 1.0; } \endverbatim
2- define a non-uniform inlet with :
groovyBC or code-stream
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 December 1, 2013, 15:37 #3 Member   Sergey Join Date: Nov 2013 Posts: 86 Rep Power: 4 Salam! Nima, thank you for you reply. I was able to run my case with inlet defined with keywords your suggested Code: ```type flowRateInletVelocity; volumetricFlowRate;``` However, the velocity profile is still uniform. Can I require velocities to satisfy no-sleep BC, i.e. zero velocities on the boundaries of the channel?

 December 1, 2013, 23:54 #4 Senior Member   Nima Samkhaniani Join Date: Sep 2009 Location: Tehran, Iran Posts: 1,147 Blog Entries: 1 Rep Power: 15 i guess so , however if you applied no-slip condition and still you have uniform velocity, then you may want to try the second option __________________ Training Course on OpenFOAM at (http://www.isme.ir/) My Weblog (http://openfoam.blogfa.com/)

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