Combustion question

Mac

As a starting point for more advanced modeling, I have set up the model given in Tutorial 9, except that I am using CH4 instead of propane. This seems to work fine. For a number of reasons, I am now trying to set all scalars to "Transport" rather than some being "Internal" as in the original tutorial. Everything seems to work fine until I change N2 to "Transport." At this point, the mass fraction of N2 changes sinusoidally from about .7 to about 1e-5 and back to roughly 0.7 from one iteration to the next. This causes the temperatures to fluctuate also.

Can someone tell me why this happens? Under "Chemical Module - Define Scheme," I have O2 set to "Transport" with a value of 0.

Mac