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-   -   Units for Contaminant Concentration (http://www.cfd-online.com/Forums/phoenics/51878-units-contaminant-concentration.html)

Rob March 25, 2005 05:40

Units for Contaminant Concentration
 
Hello. I'm trying to deal with contaminant dispersal, and I'm not quite sure what units Phoenics uses for contaminants. When I enter an initial value for C1, for example, and I specifying a mass fraction in ppm? Or, perhaps, am I specifying it in kg/m^3?

Also, how does Phoenics display C1? If I plot C1 in the VR post-processor, no units are specified, and it does not appear that I can cause them to change. What are the units in which C1 is displayed?

Also, if I create a source of C1 using PATCH and COVAL commands, what units should I use?

Thank you, Rob

cham March 30, 2005 10:06

Re: Units for Contaminant Concentration
 
C1 is a generic scalar variable, and if it used to represent a chemical species component in a gas mixture, the default units are mass fraction, i.e. kg-component/kg-mixture.

The concentration in kg-component/m^3-mixture can be determined by storing another 3d variable, say C1CO, and then multiplying C1 by the mixture density, DEN1. This is easily done by use of the following INFORM command in the Q1 file or through the VR Editor, ie:

(STORED VAR C1CO is C1*DEN1)

If you want to solve for a passive contaminant C1 in ppm by mass, then any inlet values of C1 must be in these units, i.e. multiply by 1E6.

Volumetric quantities, such a ppm by volume or mol fraction, can be deduced from the mass fraction C1 by use of the appropriate conversion formula using INFORM, as exemplified above.



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