Discovery 2020 R2: Regarding operating pressure

- August 17, 2020 at 5:38 am
  
  junyi.lee
  Subscriber
  
  Hello,
  
  Could you please confirm if the operating pressure in Ansys Discovery 2020 R2 is set to atmospheric pressure, 101325 Pa? I could not find this information in ansyshelp.ansys.com.
  When a boundary condition such as a pressure outlet is assigned with a pressure of 0 Pa, does this mean that the absolute total pressure would be 0 Pa + 101325 Pa?
  Thank you,
  
  Jun
- August 17, 2020 at 5:58 am
  
  Charudatta Bandgar
  Subscriber
  
  Hello Jun ,
  
  Jun said:
  Could you please confirm if the operating pressure in Ansys Discovery 2020 R2 is set to atmospheric pressure, 101325 Pa?
  
  That is correct.
  
  At the outlet, you can use both absolute as well as gauge pressure, as long as it is static. The measurements will be shifted by 1bar based on the pressure measurement type you are using and provided you have consistent type throughout the fluid domain. If you are specifying inlet pressure as well, then it needs to be total pressure and not static (be it absolute or gauge, as long as it is consistent with the fluid domain).
  
  Jun said:
  
  When a boundary condition such as a pressure outlet is assigned with a pressure of 0 Pa, does this mean that the absolute total pressure would be 0 Pa + 101325 Pa?
  That is right. 0Pa will be the gauge pressure.
  
  Regards.
  - August 17, 2020 at 6:37 am
    
    junyi.lee
    Subscriber
    
    Hello Charudatta Bandgar,
    
    Thank you for the quick response.
    
    If I understood correctly, Ansys Discovery will automatically adjust the operating pressure behind the scenes, based on whether we specify absolute or gauge pressure?
    
    For example, when using a velocity inlet (e.g. 1 m/s), then the pressure outlet can be either gauge pressure (e.g. 0 Pa) or absolute pressure (e.g. 101325 Pa), as long as it is static pressure?
    
    When specifying a pressure inlet, it can also be either gauge pressure or absolute pressure, just that it needs to be static + dynamic pressure? And if gauge pressure was specified at the inlet, then similarly, the outlet needs to be gauge pressure?
    
    Kind regards,
    Jun
  - August 17, 2020 at 7:14 am
    
    Charudatta Bandgar
    Subscriber
    
    Hello Jun ,
    
    Yes, that is correct. As long as the measurement method is consistent throughout the fluid domain, they are good.
    
    Regards.
- September 30, 2021 at 2:35 am
  
  Tyson Cooney
  Subscriber
  
  What about in the instance where gravity is set? With mass flow at the inlet, does the pressure at the outlet then need to be absolute?