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 sajad_abasi August 15, 2011 13:50

porous resistance

hi dear freinds.
im modelling a porous region and in the inlet i set a constant pressure.suddenly in decreased.so the mass flow decreased.i decreased the resistance of porous region by "CEL" expression to obtain the first flow rate with this new pressure.the resistance decreased but massflow is constant.

what is the problem in my modelling?
can any body guide me?

best regards/

 ghorrocks August 15, 2011 18:51

Can you describe what you are modelling, what the boundary conditions are and what you are trying to achieve?

 sajad_abasi August 16, 2011 05:35

sure.
i modelling a tube with constant diameter that have a porous domain at the end.inlet and outlet "BC" are constant pressure.at inlet when time is less than 0.2 "P=4000pa" is applied and after that inlet pressure suddenly decreased to 1000pa.at outlet "P=100pa" and is fixed during whole simulation.when inlet pressure is 4000pa the porous resistance is fixed to 10.but when it decreased to 1000 i decreased the resistance to gain the flowrate that was following in tube by pressure inlet 4000.i mean at first inlet pressure was 40000 and resistance was10 and flowrate was q1 now the inlet pressure is 1000 resistance decreased and i want again q1.

in the run after pressure decreased resistance decreased but flowrate is fix relative to p=1000

 ghorrocks August 16, 2011 06:45

Is it compressible or incompressible?

If you want to control the flow rate then why don't you use a mass flow boundary condition?

 sajad_abasi August 16, 2011 07:48

it is incompressible.
my B.Cs are presure so i can not use massflow.

i change the resistance of porous domain manualy 10,9,8,5,0.but massflow didnt change.so i think i define porous in wrong way.

could you give me a refrence or an example of modelling porous in CFX.?