Totalpressure Ansys

Leuchte · May 21, 2011, 08:32

Hello,

i have a problem with the Totalpressure in Ansys-CFX Post. I´ve drawn a Line in the center of my domain and extracted density, velocity and static pressure along this line. I imported the data in excel and calculated the Totapressure by:

p_total=p_static + (Density/2)*(Velocity^2) from my fluid mechanics script

The problem is, the calculated totalpressure is very far away from the totalpressure extracted from Ansys along the line. What is my mistake? Do i have to calculate the Totalpressure another way because of compression effects?

regards
Niklas

immortality · April 9, 2013, 04:57

you should use isentropic relations if your case is compressible.

ghorrocks · April 9, 2013, 18:56

Also keep in mind that the density, pressure and velocity variables are interpolated in your exported file, but when you use the total pressure variable in CFX it is calculated directly on the control volumes. This means your calculation will have interpolation errors in it. The CFX reported total pressure is more accurate.

May 21, 2011, 08:32	Totalpressure Ansys	#1
Leuchte New Member Niklas Join Date: Sep 2010 Posts: 7 Rep Power: 15	Hello, i have a problem with the Totalpressure in Ansys-CFX Post. I´ve drawn a Line in the center of my domain and extracted density, velocity and static pressure along this line. I imported the data in excel and calculated the Totapressure by: p_total=p_static + (Density/2)*(Velocity^2) from my fluid mechanics script The problem is, the calculated totalpressure is very far away from the totalpressure extracted from Ansys along the line. What is my mistake? Do i have to calculate the Totalpressure another way because of compression effects? regards Niklas

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April 9, 2013, 04:57		#2
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	you should use isentropic relations if your case is compressible.

April 9, 2013, 18:56		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,697 Rep Power: 143	Also keep in mind that the density, pressure and velocity variables are interpolated in your exported file, but when you use the total pressure variable in CFX it is calculated directly on the control volumes. This means your calculation will have interpolation errors in it. The CFX reported total pressure is more accurate.