Inlet species fraction mismatch at low strain rates in counterflow diffusion flame

[Alexander Haake]

Hello everyone,

I’m trying to simulate a counterflow diffusion flame at low strain rates. When I reduce the mass flow rates, I notice that the computed species fractions near the inlets no longer match the specified boundary values.

This issue is reproducible with the “Scaling of diffusion flames with pressure and strain rate” tutorial by reducing the initial mass flow rates by a factor of 30.

Has anyone else observed this behavior? Could this be a bug in the solver or the boundary condition? And is there an easy workaround or fix?

Thanks and best regards,

Alexander

Cantera: 3.1.0 (stable)

Python: 3.10.12

OS: Ubuntu 20.04.5 LTS

[Ingmar Schoegl]

Hi Alexander,

What you’re observing is expected based on a mixed boundary condition, see

https://cantera.org/stable/reference/onedim/governing-equations.html#inlet-boundary

-ingmar-

[Alexander Haake]

Is there any chance of fixing the species fraction at the boundary?

[Ingmar Schoegl]

Unfortunately, this would require a change of the underlying C++ code. So in theory this is possible.