[MNMK]

Hi everybody,

I simulated the distribution of a multicomponent material with the below mass fraction an exhaust product in the surrounding of a car.:

H2O 0.0581
N2 0.72881
O2 0.04528
CO2 0.15833
NO 0.00004
NO2 0.00002
Ar 0.00934
CO 0.00001
CxHy 0.00007

I have set a continous fluid and variable composition mixture.
What I see in the reult is that Ar component with less mass fraction(0.0094) reaches a bigger area in comparison with N2 and O2 with mass fractions 0.72881 and 0.04528, respectively.

Co2 and Ar are components that are spread to a wide area.

I expected that the component with more mass fraction would reach a bigger area. Can anyone explain to me why it happens?


regards,

[ghorrocks]

I assume this is a diffusion driven thing. Diffusion is driven by concentration gradients, not absolute values of concentrations. So if Ar has diffused further then its concentration gradient is higher. This assumes all the mass fractions have the same diffusion constant, obviously if Ar has a larger diffusion constant then it will diffuse faster.