Learning Forum

[birbara2]

Hello I want to ask what is the gauge total pressure in setting the inlet pressure boundary condition? and what is the supersonic/initial gauge pressure? and is the value specified as the amount over atmospheric pressure or the operating condition? or is it just the absolute pressure and if not absolute then can we specify it in absolute terms?

[DrAmine]

All pressure input in Fluent are gauge pressure that means relative to the operating pressure. Example at your inlet you have 1 atm: Either you provide 0 Pa Gauge pressure and set operating pressure to 1 atm or the inverse or a combination

p_absolute=p_gauge+p_operating. P_gauge is the static pressure variable available for post-processing.

For subsonic flow solver expects that you provide 4 of 5 required boundary conditions (considering only momentum).The solver will provide the latter one (think about the method of the characteristics-a wave travelling out of the domain) For supersonic you need to provide everything (that means 5 for 3D only momentum). That is why for supersonic flow your input in supersonic/gauge pressure is used within the solver stage. For subsonic flow you can use that flow for the initialization if you hit "initialize" from your Inlet.