Reply To: outlet type in boundary conditions

[NickFL]

How do I prevent the back flow temperature from being used so that I can find out the temperature at the outlet every certain time (transient) using the pressure-outlet? because I entered the velocity-inlet and pressure-outlet with a back flow temperature of 300K and the result is a temperature at the outlet of 300K (meaning the back flow temperature is active).

Does it report a “Reversed Flow on ### of faces (X% area) of pressure-outlet” when solving? This is telling you how much of the outlet has flow returning to the domain. These numbers should be small or ideally not even reported because they are zero. One way to remove them is to extend your domain so that all the flow is leaving an not entering where you have an exit. 

btw does this also apply to the boundary condition outflow type? because I also tried using velocity-inlet and outflow and the result is that the temperature at the outlet follows the temperature that I input in the velocity-inlet

Generally it is a good practice to avoid the outlfow type boundary condition in Fluent. Read the link SRP provided above.

I should mention that my statement above about have the pressure/velocity conditions at the outlet/inlet is for subsonic flow. The mathematics of compressible flow require the conditions upstream.