areaAve(Pressure) with back flow

Axlex · August 20, 2014, 10:33

Hey,

i have a problem regarding the right pressure measurement of areaAve.

I have a pipeflow arrangement like shown in attachement 1. The diameter suddenly decreases.

Now i am trying to get the pressure distribution along the pipe. I create a plane and move it along the pipe, taking the area averaged pressure at every step. The result is shown in attachement 2.

How can i get rid of this downswing? My guess is, that it is probably because there is a backflow around the core flow like shown in attachement 1.

any suggestions are appreciated.

ghorrocks · August 20, 2014, 19:43

This is real - the flow is accelerating in the vena contractor and has a locally reduced pressure.

If you want to get rid of this then use a rounded pipe entry. Make sure the radius is large enough that it does not separate. Or even better use a more optimal shape like an elliptical profile.

Axlex · August 21, 2014, 07:37

Thank you for your answer.

In fact wasn't looking for a solution to prevent the separation, but for a way to get the "right" pressure distribution. I obviously did not make it clear enough.

But thank you anyway, because it reminded me of a person named Daniel Bernoulli, who said that there is not only the static pressure, which i get from areaAve(Pressure), but also the dynamic pressure.

singer1812 · August 21, 2014, 12:05

massFLowAve(Total Pressure)?

Are you trying to compare this to something?

August 21, 2014, 07:37		#3
Axlex New Member Robert Join Date: Apr 2013 Posts: 24 Rep Power: 13	Thank you for your answer. In fact wasn't looking for a solution to prevent the separation, but for a way to get the "right" pressure distribution. I obviously did not make it clear enough. But thank you anyway, because it reminded me of a person named Daniel Bernoulli, who said that there is not only the static pressure, which i get from areaAve(Pressure), but also the dynamic pressure. __________________ Regards Robert

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August 20, 2014, 19:43		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	This is real - the flow is accelerating in the vena contractor and has a locally reduced pressure. If you want to get rid of this then use a rounded pipe entry. Make sure the radius is large enough that it does not separate. Or even better use a more optimal shape like an elliptical profile.

August 21, 2014, 12:05		#4
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 21	massFLowAve(Total Pressure)? Are you trying to compare this to something?