here's a though one (combustion)
 

I'm trying to model the following reaction H2+0.5O2->H2O within a cilindrical chamber of 5mm length and 5mm diameter. Inlet on one side of 1mm diameter (cenetred) and outlet on the other side (5mm). The incoming air is actually 0.111 H2 and 0.889 O2 (mass fractions/premixed) I can't use eddy break-up model due to low-Reynolds numbers (inlet vel 1m/s).

I which to model the direct reaction in laminar flow but some negative densities apear in the star-up iterations...

any suggestions?

Using STAR-CD code

THNX!