Learning Forum

[AMDB007]

Hi,

I am doing a supersonic combustor duct flow analysis, with combustion (species transport) and have a doubt about its boundary conditions.

I know the inlet conditions of both my air inlet and fuel inlet i.e. velocity, pressure, and temperature and the mass fractions. But I do not know the pressure, velocity nor the temperature for the outlet.

So what boundary conditions will suit my needs?

I was thinking to go with pressure far-field for the inlets and the outlet, where I will set the available parameters for the inlets, and leave the outlet pressure, velocity & temperature to be blank i.e."0"

So if I set it like that, will fluent take into consideration the flow parameters from the inside of the combustor while solving and come up with the flow condition that should be for the outlet on its own?

Or is there any rule that I should always set the values for all the parameters even in the outlet before hand?

Thank you

[aitor.amatriain]

Temperature is not needed at the outlet, as ANSYS Fluent uses Neumann BCs for temperature
In regards to pressure and velocity, it is recommended to extend the domain far enough so that ambient pressure is reached at the outlet. In this situation, you should consider pressure-outlet BC with pressure equal to ambient pressure.

[AMDB007]

Thank you, I will choose pressure-outlet BC and set pressure to ambient.
So if temperature is not needed at the outlet, when pressure-outlet is chosen the temperature is set to 300k as default. Can I make it "0"?

[aitor.amatriain]

300K is the total temperature for reverse flow. If reverse flow is expected, I usually set the total temperature for reverse flow equal to the ambient total temperature.

[AMDB007]

Okay, thanks

[Muhammad Moazim Ali]

Hello sir

Should we have to enter the mass fraction for the outlet species or ansys can calculate by itself?