Hi,

I am using fluent to simulate combustion of gas. I use ideal gas model.I don't know how to define outlet boundary(supersonic) .If I define it as pressure-out boundary, I don't know the mass fraction of the gas at outlet.

In the tut 8 "chemical mixing and gaseous combustion",Why should they just define the mass fraction of O2,and don't define the mass fraction of other gas at pressure-out boundary?

Thank you. Any ansnwer will be welcome.

Devy 2001.5.24

You are calculating the species composition at the exit. However, the scalar (turbulence, species, etc.) BCs are set by the user at the outlet in the event of backflow, i.e. flow from outside your computational domain returning to the computational domain. Ideally, you should position your outlet boundary such that you avoid this scenario thereby reducing the uncertainty in your simulation results.

Hi,

If you can expalin your problem a bit more, it can be easy to understand and address it. Did you check at your Flux reports. The Mass flux give you an idea how much is going in and out, and what level your esiduals are converged. Also can you expalin why you prefered to use a Coupled solver. sundar.