pressure outlet condition setup
 

Hi,

I am a beginner for Fluent simulation, I confused when I deal with the outlet condition.

Recently, I am simulating a buoyancy flow heated on the on the ground level, and then move upwards in a virtical chimney with Boussinesq model. Following the Flunet mannul, I have used the pressure boundary conditions in both of the inlet and outlet. In my physical model, the inlet static pressure is equal to the ambient pressure at the ground level (namely, 1 atm), while outlet static pressure is also equal to the value of the ambient at the same altitude (~0.97 atm in 195m-height). As the operating pressure is set to 1atm in the Define/operating condition, I set the gauage pressure at inlet to 0 Pa, and the outlet gauge pressure to -2340 pa, respectively. However, the virtical max velocity outcome under this conditions is unreasonably high (44m/s in simulation V.S. 15 m/s in a real experiment)

So, my Question is: given the chimney is 195 meters high, how to set the gauge pressure at the outlet? Should I take consideration with the pressure gradient due to the gravity?

Thx in advance.

Ray