Time averaged pressure in transient rotor-stator simulation

lowdo · June 16, 2020, 07:20

I'm running a transient case in CFX using the transient rotor-stator model. I'd like to output time averaged values of certain variables, particularly pressure.

After reading various other posts on this forum, I've turned on the Transient Statistics option in CFX-Pre. I've created a Transient Statistics object, in which I've selected the variables I want to average.

The trouble is, when I open the results in CFD-Post, the variables listed in the Transient Statistics part don't match what I specified in CFX-Pre. Particularly, there is no Pressure variable - only 'Pressure.Gradient', with units of kg m^-2 s^-2 (dp/dx?)

Am I missing something here? Is it possible to do what I'm trying to do?

Thanks,

Chris

lowdo · June 16, 2020, 08:05

Ignore me - I was somehow missing the 'Arithmetic Average' sub-menu that includes these values

ghorrocks · June 16, 2020, 08:40

Pressure gradient is the spatial gradient of pressure, dp/dx as you state. It is not a transient statistic. Are you sure you correctly activated the transient statistics? They should be available as variables in post processing if you did. I think they have the suffix ".trnavg", so they are pretty obvious.

Finally, have you looked under the curiously titled "..." button for the additional variables available under there? They could be hidden in there.

lowdo · June 16, 2020, 08:43

Hi Glenn,

Yes, thanks - having had a look again I realised I was looking at the wrong part of the menu. I thought things like pressure.gradient were part of the Transient Statistics list, but after posting realised that was not so. I've managed to find the transient average values now.

Thanks,

Chris

June 16, 2020, 07:20	Time averaged pressure in transient rotor-stator simulation	#1
lowdo New Member Chris Join Date: Feb 2013 Posts: 17 Rep Power: 13	I'm running a transient case in CFX using the transient rotor-stator model. I'd like to output time averaged values of certain variables, particularly pressure. After reading various other posts on this forum, I've turned on the Transient Statistics option in CFX-Pre. I've created a Transient Statistics object, in which I've selected the variables I want to average. The trouble is, when I open the results in CFD-Post, the variables listed in the Transient Statistics part don't match what I specified in CFX-Pre. Particularly, there is no Pressure variable - only 'Pressure.Gradient', with units of kg m^-2 s^-2 (dp/dx?) Am I missing something here? Is it possible to do what I'm trying to do? Thanks, Chris

June 16, 2020, 08:40		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Pressure gradient is the spatial gradient of pressure, dp/dx as you state. It is not a transient statistic. Are you sure you correctly activated the transient statistics? They should be available as variables in post processing if you did. I think they have the suffix ".trnavg", so they are pretty obvious. Finally, have you looked under the curiously titled "..." button for the additional variables available under there? They could be hidden in there. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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June 16, 2020, 08:05		#2
lowdo New Member Chris Join Date: Feb 2013 Posts: 17 Rep Power: 13	Ignore me - I was somehow missing the 'Arithmetic Average' sub-menu that includes these values

June 16, 2020, 08:43		#4
lowdo New Member Chris Join Date: Feb 2013 Posts: 17 Rep Power: 13	Hi Glenn, Yes, thanks - having had a look again I realised I was looking at the wrong part of the menu. I thought things like pressure.gradient were part of the Transient Statistics list, but after posting realised that was not so. I've managed to find the transient average values now. Thanks, Chris