[MachZero]

Combustion community,

I am having a really troubling problem. I am simulating combustion in Fluent using the non-premixed model. I have two inlets fuel streams and a single oxidizer stream. When I model the combustion, I get spikes in my turbulence and continuity residuals every 10-20 iterations, but the outlet temperature converges well and the heat flux balance at the end of the run is close to zero.

Then I add in a heat flux through the walls, using an exterior heat transfer coefficient and bulk temperature. Once this happens, the outlet temperature has swings of up to 100 degrees C and the heat balance way off balance.

I have been working this model for days (long, 12+ hour days) with almost no progress. Has anyone seen this, or have any ideas why this might be occurring?

ANY ideas are welcome!

I have added some plots of outlet temperature fluctuations and residuals