modelling a fan on a Boundary patch

coroi · September 23, 2014, 11:38

Hi OpenFOAMers,

I would like to know your opinion on how to model a fan via boundary conditions already existing in OpenFOAM.
My purpose is to get a fixed flowrate on the Fan_patch, in order to model the ventilation in a room.The direction of the flow points outwards the room.
I was thinking to set a outletInlet BC in the file 0/U for the patch and fixedValue BC for the pressure.

I tried to implement the existing fan BC (according to the TJuctionFan tutorial in OpenFOAM2.1.1 ) and fanPressure BC but my computations stop at the 1st time iteration, the solver fireFoam crashes because a "floating point" exception" signal is sent to the CPU.The solution isn't normally diverging because the max Courant number is 0.0008 << 0.5 .
Does anyone have any suggestions/comments on how to model the fan on a boundary patch or how to make work the fan/fanPressure BC on interior baffles??

I'll appreciate any help!!
Thank very much for all your posts on that forum!!Some of them ae very helpful!

jherb · October 30, 2014, 10:01

If you want a fixed flow rate, why don't you use a standard boundary condition for the velocity? You could try fixedMean (to only specify the mean value of the outflow) or surfaceNormalFixedValue (be careful with the sign/direction).

September 23, 2014, 11:38	modelling a fan on a Boundary patch	#1
coroi New Member Join Date: Dec 2013 Posts: 12 Rep Power: 12	Hi OpenFOAMers, I would like to know your opinion on how to model a fan via boundary conditions already existing in OpenFOAM. My purpose is to get a fixed flowrate on the Fan_patch, in order to model the ventilation in a room.The direction of the flow points outwards the room. I was thinking to set a outletInlet BC in the file 0/U for the patch and fixedValue BC for the pressure. I tried to implement the existing fan BC (according to the TJuctionFan tutorial in OpenFOAM2.1.1 ) and fanPressure BC but my computations stop at the 1st time iteration, the solver fireFoam crashes because a "floating point" exception" signal is sent to the CPU.The solution isn't normally diverging because the max Courant number is 0.0008 << 0.5 . Does anyone have any suggestions/comments on how to model the fan on a boundary patch or how to make work the fan/fanPressure BC on interior baffles?? I'll appreciate any help!! Thank very much for all your posts on that forum!!Some of them ae very helpful!

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October 30, 2014, 10:01		#2
jherb Senior Member Joachim Herb Join Date: Sep 2010 Posts: 650 Rep Power: 22	If you want a fixed flow rate, why don't you use a standard boundary condition for the velocity? You could try fixedMean (to only specify the mean value of the outflow) or surfaceNormalFixedValue (be careful with the sign/direction).