Pressue in CFD post is Relative or Absolute pressure?

shivasluzz · June 5, 2015, 02:11

The pressure and total pressure values in cfd-post are relative pressure or absolute pressure?
I have gone through many post still it is confusing. Please clarify

Thomas MADELEINE · June 5, 2015, 05:41

Static Pressure is relative pressure
Absolute Pressure is well... absolute pressure
and Total Pressure is Total Pressure (static + dynamic). It is absolute like the Pressure.

For more details see the help in ANSYS CFX theory guide 1.1.3 then Pressure or Total Pressure

shivasluzz · June 5, 2015, 08:24

thanks Thomas for your reply...
so, if i used some reference pressure other than 0, then my total pressure is total pressure (from cfd post) + reference pressure used.. am i right?

Thomas MADELEINE · June 5, 2015, 09:19

No.
quote from ANSYS Help:
The terms Pressure and Total Pressure are absolute quantities and must be used to derive the Total Pressure when using an equation of state (compressible) formulation (particularly for Equation 1–48).

soumitra2102 · June 4, 2019, 08:33

Thanks for the information

Pree1032 · March 25, 2020, 11:57

So, there is an option called Absolute Pressure that exports the STATIC PRESSURE+ REFERENCE PRESSURE, but if i want to export TOTAL Pressure + REFERENCE Pressure, what should I do? I have given Reference pressure as 1 atm.

Opaque · March 25, 2020, 17:24

There is no option available for "Absolute" Total Pressure

You can just add the Reference Pressure to Total Pressure, and you should be fine.

Pree1032 · March 25, 2020, 17:32

Thank you! Just needed to clarify that. And I'm new to this site and I didn't know where to post my question, so I added it as a reply in this thread!

June 5, 2015, 02:11	Pressue in CFD post is Relative or Absolute pressure?	#1
shivasluzz Senior Member sluzzer Join Date: Jul 2014 Posts: 146 Rep Power: 12	The pressure and total pressure values in cfd-post are relative pressure or absolute pressure? I have gone through many post still it is confusing. Please clarify

June 5, 2015, 05:41		#2
Thomas MADELEINE Senior Member Thomas MADELEINE Join Date: Oct 2014 Posts: 126 Rep Power: 12	Static Pressure is relative pressure Absolute Pressure is well... absolute pressure and Total Pressure is Total Pressure (static + dynamic). It is absolute like the Pressure. For more details see the help in ANSYS CFX theory guide 1.1.3 then Pressure or Total Pressure Oussama likes this. Last edited by Thomas MADELEINE; June 5, 2015 at 05:46. Reason: wrong emplacment of help paragraph

March 25, 2020, 11:57	How to get the total pressure contour using absolute pressure values?	#6
Pree1032 New Member Preethi Join Date: Feb 2020 Posts: 4 Rep Power: 6	So, there is an option called Absolute Pressure that exports the STATIC PRESSURE+ REFERENCE PRESSURE, but if i want to export TOTAL Pressure + REFERENCE Pressure, what should I do? I have given Reference pressure as 1 atm.

March 25, 2020, 17:24		#7
Opaque Senior Member Join Date: Jun 2009 Posts: 1,880 Rep Power: 33	There is no option available for "Absolute" Total Pressure You can just add the Reference Pressure to Total Pressure, and you should be fine. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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June 5, 2015, 08:24		#3
shivasluzz Senior Member sluzzer Join Date: Jul 2014 Posts: 146 Rep Power: 12	thanks Thomas for your reply... so, if i used some reference pressure other than 0, then my total pressure is total pressure (from cfd post) + reference pressure used.. am i right?

June 5, 2015, 09:19		#4
Thomas MADELEINE Senior Member Thomas MADELEINE Join Date: Oct 2014 Posts: 126 Rep Power: 12	No. quote from ANSYS Help: The terms Pressure and Total Pressure are absolute quantities and must be used to derive the Total Pressure when using an equation of state (compressible) formulation (particularly for Equation 1–48).

June 4, 2019, 08:33		#5
soumitra2102 Member Soumitra Vadnerkar Join Date: Aug 2018 Posts: 70 Rep Power: 8	Thanks for the information

March 25, 2020, 17:32		#8
Pree1032 New Member Preethi Join Date: Feb 2020 Posts: 4 Rep Power: 6	Thank you! Just needed to clarify that. And I'm new to this site and I didn't know where to post my question, so I added it as a reply in this thread!