# Transient analysis to 3D Water Pipe system with Valve and Pump

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 May 15, 2018, 10:33 Transient analysis to 3D Water Pipe system with Valve and Pump #1 New Member   Kim Gunhyeong Join Date: May 2018 Location: Seoul, Korea Posts: 9 Rep Power: 8 I separate all domain into "Valve(spherical shape fluid domain which has valve-shaped empty space in)" and "pipe(Remainder)". "Valve" will turn 90 degrees along normal axis of upper drawing during 1.5s and will stop, so valve is finally open(rotating-stationary interface) Diameter of valve is 140 mm, so fluid can initially flow to some extent between the valve and the pipe. Boundary conditions are: Inlet : Total pressure 0.3 MPa(Pump), Outlet : mass flow rate 28.6 kg/s(fluid velocity is 0.4 m/s at all domain) global initialization is: velocity 0 static pressure 0 at all domain I have some questions. 1)Is it possible to change outlet BC to static pressure, 1 Atm? If possible, how do I set up global initialization? How do I set the initial values ​​of the pressure based on the height of each point in the all domain? 2)What rotational model should I apply to a rotating spherical interface? Plz help me. I try to solve this model, but overflow occured.

 May 15, 2018, 18:36 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,732 Rep Power: 143 1) Yes, you can use 1 atm outlet static pressure. You don't need to do anything special for the initial condition, CFX will sort it out as it solves. If the static head is important and you have enabled gravity then you should read the documentation on this, as CFX removes the static head from the pressure calculation so you don't need to include it explicitly. 2) If you are modelling the valve opening in a transient simulation then use transient-rotor stator. Overflow: FAQ - https://www.cfd-online.com/Wiki/Ansy...do_about_it.3F __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

May 16, 2018, 17:46
#3
New Member

Kim Gunhyeong
Join Date: May 2018
Location: Seoul, Korea
Posts: 9
Rep Power: 8
Quote:
 Originally Posted by ghorrocks 1) Yes, you can use 1 atm outlet static pressure. You don't need to do anything special for the initial condition, CFX will sort it out as it solves. If the static head is important and you have enabled gravity then you should read the documentation on this, as CFX removes the static head from the pressure calculation so you don't need to include it explicitly. 2) If you are modelling the valve opening in a transient simulation then use transient-rotor stator. Overflow: FAQ - https://www.cfd-online.com/Wiki/Ansy...do_about_it.3F
Thank you for your answer. In the case of 2), it works!

 Tags overflow, pump, rotation, transient