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Old   December 6, 2017, 05:37
Default Chem_SRC Passive Units
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Rajat soni
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Hello everyone,

I am doing a rather simple stationary simulation with chemistry and I have added non-transporting passive, "CHEM_SRC", to track the chemical heat release flux in each cell. The units I am getting in passive.out for this passive are kg/m^3. Can anyone explain why I am getting these units and what is the scaling factor to change the units to J/s-m^3.

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Old   January 3, 2018, 11:45
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Yunliang Wang
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Sorry for the late response since we missed this one. Passives can be anything and can have any units. We know the unit of chem_src. However, we don't know the units of the passives that the user defines. Therefore, in passive.out the code simply treats the passives as mass fractions. This is true for soot and NOx. The units for soot and NOx are kg and kg/m^3 in passive.out. For chem_src the correct units for the two columns should be j/(s-m^3).kg (total amount over the domain) and j/s-m^3).kg/m^3 (averaged mean value over the domain).


Yunliang Wang
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Last edited by ywang89; January 12, 2018 at 10:39.
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Old   January 5, 2018, 08:06
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Rajat soni
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Hi Yunliang,

thanks for the reply.

What I have understood from your reply is that the kg in passive.out refers to J/(s-m^3) and kg/m^3 refers to the volume average mean value.
I want to compare boundary heat flux(j/s) with chemical heat release rate (j/s). So, if I am getting it right then the value of CHEM_SRC, also in post*.out gives the value of passive in kg (corresponding to J/s-m^3) for each cell. Further, to get the chemical heat release rate for each cell, shall I simply multiply CHEM_SRC with volume of the corresponding cell?

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chem_src, passive, unit conversion

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