# Gas generation with resistance in porous media

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 August 30, 2005, 05:20 Gas generation with resistance in porous media #1 billow Guest   Posts: n/a Hello: I got a curious result in my case recently. wish someone could help me. My case is simulate the gas generating and flowing in porous media. In my Q1 file I set these lines: ------------------------------------------------ PATCH (SOR1 ,VOLUME,1,NX,1,NY,1,NZ,1,1) COVAL (SOR1 ,P1 , FIXFLU , 2.400000E-07) PATCH (SOR2 ,VOLUME,1,NX,1,NY,1,NZ,1,1) COVAL (SOR2 ,W1 , 1.345000E+07, 0.000000E+00) ---------------------------------------------------- I set the domain matiral as 'Air useing ideal gas law', and, it was 'one_phase,one dimension'. which i want to do is set gas generate in whole domin(size:1m*1m*50m) with rate 2.40E-07(m**3/m**3.S). And there were resistance presented by PATCH 'SOR2'(in porous media which μ/K = 1.345000E+07). In my mind , in result file the Nett source of R1 at patch named: SOR1 should be 2.40E-07*Volume = 2.40E-07*1*1*50 =1.20E-05, but the reality is: --------------------------------------------------- Nett source of R1 at patch named: SOR1 = 3.967191E-02 --------------------------------------------------- that makes me so puzzled, and have no idea with it ps:the result is right when i set the domain matiral as water(imcompressable) OR delete the Patch named SOR2(resistance)

 August 30, 2005, 05:30 Re: Gas generation with resistance in porous media #2 billow Guest   Posts: n/a sorry, the unit of generation rate is (Kg/m**3.S), I write it incorrectly above.

 September 8, 2005, 04:49 Re: Gas generation with resistance in porous media #3 Mike Guest   Posts: n/a My suspicion is that the contribution -Pp*V*Cm, which is usually negligible, is responsible for the incorrect gas generation inflow rate. The source term is: Sm = Cm*(Vm-Pp)*V and since Cm=FIXFLU=2.E-10, the contribution -2.E-10*Pp*V is usually negligible compared to 2.E-10*Vm*V/2.E-10 where Vm is the mass generation rate per unit volume. However, in a porous media the in-cell pressure may be quite large. A hand check of your RESULT should be able to ascertain whether this surmise is correct. If proved correct, you need to use a much smaller value of FIXFLU, say 1.E-20, to render the contribution -Pp*V*Cm negligible.

 September 9, 2005, 10:36 Re: Gas generation with resistance in porous media #4 billow Guest   Posts: n/a Thanks for your help, and I think that is the right point. Through my experiment I found that the Coefficient FIXFLU can convert the Value to source/Coefficient automatically. So it is necessary to set Value= source/1.0E-20 manually when I set the Coefficient = 1.0E-20. Is that right? But I really got a right RESULT

 September 20, 2005, 08:51 Re: Gas generation with resistance in porous media #5 mick Guest   Posts: n/a No in ground or elsewhere should not need to set VAL=VAL/FIXFLU, this should be done automatically inside the code. But you can tell at a glance from your results as the source would be incredably wrong.

 June 21, 2011, 18:11 #6 New Member   zohreh Join Date: Feb 2011 Location: Tehran Posts: 20 Rep Power: 6 I want to model a micro filter, This filter (membrane) is rectangular (10×5 cm) with the thickness 12e-5. so,I calculate this parameters from Ergun equation which D=1e-6, because of the Micro filter type. is this assumption true?? i think this is very thin filter so there in not flow through in the membrane, in this situation is inertial coefficieant higher in Y direction? or not?when i set y-direction inertial coefficient higher than x-direction got better answer! is this resonable? I am looking forward to hearing from you. Sincerely yours

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