SORSCA & FLUINJ

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 January 28, 2008, 04:30 SORSCA & FLUINJ #1 KK Guest   Posts: n/a Sponsored Links Hi, STAR-CD experts! Now, I am trying to make user subroutine to perform CFD of fuel cell using STAR-CD platform. I'd like to ask one thing regarding on STAR-CD user subroutine. My problem is that the sum of scalars is not equal to 1. For example,in the anode side, H2 and H2O are being consumed there. So, I have assign those sink terms in SORSCA.f and also I assigned the corresponding mass sink in FLUINJ.f. However, I could not get the total mass fraction of 1.0. Is there anything to do to implement the scalar source/sink correctly? Berief summary of my setting is as follows: (Here, I assume the sink is constant) background fluid: H2 (density=ideal, viscosity=multicomp) additional scalar 1: SC1 = H2 (passive) additional scalar 2: SC2 = H2O (active) Both of two SC are solved through 'transport' eq. in SORSCA.f if (ICTID.EQ.2) then if (IS.EQ.1) S1P = -2.0 if (IS.EQ.2) S1P = -1.0 endif in FLUINJ.f if (ICTID.EQ.2) then FLUXI = -3.0 endif

 January 29, 2008, 06:01 Re: SORSCA & FLUINJ #2 Richard Guest   Posts: n/a The problem is that FLUINJ cannot selectively extract scalars: it just extracts them in proportional to the cell concentration. So if you specify FLUXI=-3.0 and the concentrations are SCALAR(1)=0.1, SCALAR(2)=0.9, then you will be extracting 0.3 kg/m3/s of SCALAR(1) and 2.7 kg/m3/s of SCALAR(2). If this is what you want to do then you do not need a SORSCA. On the other hand, you need a SORSCA if you want to extract scalars disproportionately. The SORSCA corrects the FLUINJ, it doesn't replace it. To extract 2 kg/m3/s of SCALAR(1) and 1 kg/m3/s of SCALAR(2), having specified FLUXI=-3.0 in FLUINJ, then you would add FLUXI*SCALAR to S1P in your SORSCA; if FLUXI is positive it can go into S2P instead. Obviously you need to calculate FLUXI in SORSCA again too. With this coding, you should find that: - if you add the sources for scalars 1 and 2, you get zero. SORSCA is not adding or removing mass, only FLUINJ does that. - if the target sources are consistent with cell concentrations, you should find S1P = 0. - it diverges very quickly if you try to extract a scalar faster than is physical, i.e. the cell becomes "empty".

 January 30, 2008, 07:43 Re: SORSCA & FLUINJ #3 KK Guest   Posts: n/a Dear Richard, Really appreciated your kind explanation and comments. Thanks. KK

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