# Total specie mass instead of local concentration

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 May 12, 2006, 03:09 The output files of combustion #1 Member   Tomislav Sencic Join Date: Mar 2009 Posts: 42 Rep Power: 9 The output files of combustion/chemistry solvers, beside others, are species concentrations (O2, N2, CO2, CO...), with a list of local concentration in each cell. The problem is that bigger cells contribute to the global concentration more than the small ones, so just calculating the average does not lead to the correct result. In addition, in engine solvers cell volume changes with time. How can be obtained the average concentration over the hole domain? Or, how could I output specie mass instead of concentration? Where can I find the cell volumes?

 May 12, 2006, 03:35 The cell volumes are available #2 Assistant Moderator   Bernhard Gschaider Join Date: Mar 2009 Posts: 3,931 Rep Power: 41 The cell volumes are available via mesh.V() (Look at table 2.1 in the Programmers guide; it's small but most useful). Average concentration would be Yavg=sum(Y[specIndex]*mesh.V())/sum(mesh.V()); __________________ Note: I don't use "Friend"-feature on this forum out of principle. Ah. And by the way: I'm not on Facebook either. So don't be offended if I don't accept your invitation/friend request

 May 12, 2006, 03:37 the solvers write out the spec #3 Member   stefan Join Date: Mar 2009 Posts: 96 Rep Power: 9 the solvers write out the species mass fraction of each cell. If you want to know the global mass of a specie just sum up the specie mass fraction of each cell you will get the right result: mathematical writing: m_k_tot = Sum_j(m_kj) = Sum_j(rho_j*Y_kj*V_j) k is the species index j is the cell index hth You can get the cell volumes from 'mesh.V()'

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