Learning Forum

[Abbas2020]

Hi everyone,

In the pressure outlet dialog box, I would like to know what type of boundary condition is applied to the energy equation. Regardless of the backflow temperature which is used in the case if there is a backflow that occurs in the outlet section.

As far as I know, there is another boundary condition for outlet available in Fluent called " Outflow condition" in which it is assumed a zero-gradient condition for all variables including temperature.

Can anyone tell if this zero-gradient is applied also for temperature within the " pressure outlet condition"?

[Rob]

If you have reverse flow the pressure boundary will add material at the temperature you specify. The old outflow boundary shouldn't be used, and I've not used it since Fluent 4.

[Abbas2020]

I don't understand, how the pressure boundary will add material?

[Abbas2020]

This temperature specified in the pressure boundary is for backflow occurring in the outlet section. In case, there is no backflow, what will be taken as a boundary in the outlet section for the energy equation?

[Rob]

If there's no backflow the boundary temperature won't do anything. By add material I mean flow enters through the outlet in the reverse flow condition: material is added to the domain.

[Abbas2020]

OK.
But in the case of conjugate heat transfer simulation between two fluids and a solid wall, does the energy equation need to include a temperature boundary for the diffusion term in the outlet? or thefluent with pressure-outlet boundary conditions also considers a zero-gradient temperature?.

[Amine Ben Hadj Ali]

If no backflow occurs we assume high Peclet Number and hence temperature gradient is zero at outlet.