# butterfly valve

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 July 2, 2012, 13:15 butterfly valve #1 New Member   Amir sadeghi pour marvi Join Date: Dec 2011 Posts: 25 Rep Power: 7 I'm simulating a butterfly valve. multi phase Testing was conducted in 18-inch water pressure drop is measured. 24 inches of water pressure in my simulation is achieved. What causes this difference?

 July 2, 2012, 14:44 #2 Member   Luis Filipe Fabiani Join Date: Apr 2009 Posts: 43 Rep Power: 10 How was the pressure drop measured? Does the fluid goes to a reservoir or just recirculates back to the inlet? The pressure drop was measured just before and just after the valve? Or was the outlet and inlet pressure of a pump? If you just setup the outlet pressure as 0 Pa, the software does not take in account the pressure drop of an expansion after the duct you are simulating. What is the speed at the outlet? According to "Memento Des Pertes de Charge" If the speed is around 2 m/s, it is already enough to cause the 6 inches of aditional pressure drop.

 July 2, 2012, 14:45 #3 Member   Luis Filipe Fabiani Join Date: Apr 2009 Posts: 43 Rep Power: 10 Also, multiphase flows are tricky What exactly are you simulating?

 July 2, 2012, 18:50 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,805 Rep Power: 107 This is an FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

July 3, 2012, 06:49
#5
New Member

Join Date: Dec 2011
Posts: 25
Rep Power: 7
Quote:
 Originally Posted by lffabiani How was the pressure drop measured? Does the fluid goes to a reservoir or just recirculates back to the inlet? The pressure drop was measured just before and just after the valve? Or was the outlet and inlet pressure of a pump? If you just setup the outlet pressure as 0 Pa, the software does not take in account the pressure drop of an expansion after the duct you are simulating. What is the speed at the outlet? According to "Memento Des Pertes de Charge" If the speed is around 2 m/s, it is already enough to cause the 6 inches of aditional pressure drop.
The pressure drop was measured just before and after the valve.
i setup the outlet pressure as 0 Pa.
i do not have any information at outlet...
air was aspirated through the butterfly valve.Distilled water was introduced upstream of valve.

 July 3, 2012, 13:15 #6 Member   Luis Filipe Fabiani Join Date: Apr 2009 Posts: 43 Rep Power: 10 Better check the FAQ that Glenn suggested

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