Calculate concentrations that change by orders of magnitude.

Triggin · June 18, 2018, 04:22

Hi to everyone

I have a very simple question, but i couldn't find any answer to that so far...

Lets say: you have a domain which contains oxygen (concentration of 21% - therefore air) and an inlet which flushes the domain with nitrogen.
Due to an imperfect system, the stationary concentration at a certain point is 100 ppm.

21% O2 (= 210'000 ppm) compared to 100 ppm is 2100 times bigger.

If you do measurements and compare those to the simulation results, what is the accuracy you expect at that low concentration point?

Usually one can say a simulation should achieve an accuracy of lets say 10%. But what are those 10% referenced to? To the highest value (21%) or to the local value (100 ppm) ?

Any discussion would be appreciated

Best, Triggin

Triggin · June 21, 2018, 03:19

Has no one had a similar experience...?

June 18, 2018, 04:22	Calculate concentrations that change by orders of magnitude.	#1
Triggin New Member manu ebn Join Date: Aug 2015 Location: Switzerland Posts: 18 Rep Power: 11	Hi to everyone I have a very simple question, but i couldn't find any answer to that so far... Lets say: you have a domain which contains oxygen (concentration of 21% - therefore air) and an inlet which flushes the domain with nitrogen. Due to an imperfect system, the stationary concentration at a certain point is 100 ppm. 21% O2 (= 210'000 ppm) compared to 100 ppm is 2100 times bigger. If you do measurements and compare those to the simulation results, what is the accuracy you expect at that low concentration point? Usually one can say a simulation should achieve an accuracy of lets say 10%. But what are those 10% referenced to? To the highest value (21%) or to the local value (100 ppm) ? Any discussion would be appreciated Best, Triggin

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June 21, 2018, 03:19		#2
Triggin New Member manu ebn Join Date: Aug 2015 Location: Switzerland Posts: 18 Rep Power: 11	Has no one had a similar experience...?