Modelling an initially closed valve which a fluid opens

siw · April 25, 2014, 07:12

Hi,

Is it possible to model the flow through a valve system using the 1DoF solver and ANSYS Meshing remeshing when at the start of the simulation the valve is in its fully closed position - no fluid can pass through the valve?

Initially the fluid pressure on the upstream and downstream sides of the valve are equal and the valve is closed. As the simulation starts the pressure on the downstream side linearly decreases over time (I specify that with a CFX Function for the Outlet) and when the pressure difference is enough to overcome the valve spring stiffness then it starts to open and fluid flows through the valve. But at the time when the valve first starts to open this region would need to be filled with a mesh as it would not have a mesh initially since there would not be a fluid volume. The upstream region is an initially fixed volume of fluid which is evacuated through the valve during the simulation - the fluid is sucked out of the upstream region due to the specified decreasing downstream pressure.

The only data known about the valve is its geometry and spring stiffness (constant). It is not known at any given time the amount that the valve will be open - that's part of the reason for doing the simulation.

Everything I can find so far has 1) steady analysis of a valve that is open and does not move, 2) a valve displacement that is defined at given time points or 3) the valve is initially open (not initially closed) and its motion is driven by the fluid with a 1DoF solver.

Thanks

ghorrocks · April 26, 2014, 07:32

It is tricky to model changes of state (ie closed to open).

You might be able to get around it by starting with the valve open just a fraction - not enough to let a significant amount of flow through. Then the valve can open from there and you do not have to model the opening event.

Alternatively you can use the domain interface conditional opening feature to crack something open.

A further alternative is to use dynamic remeshing to handle the opening. It will take some careful planning to handle the new regions which appear as the valve opens.

April 25, 2014, 07:12	Modelling an initially closed valve which a fluid opens	#1
siw Senior Member Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 739 Rep Power: 26	Hi, Is it possible to model the flow through a valve system using the 1DoF solver and ANSYS Meshing remeshing when at the start of the simulation the valve is in its fully closed position - no fluid can pass through the valve? Initially the fluid pressure on the upstream and downstream sides of the valve are equal and the valve is closed. As the simulation starts the pressure on the downstream side linearly decreases over time (I specify that with a CFX Function for the Outlet) and when the pressure difference is enough to overcome the valve spring stiffness then it starts to open and fluid flows through the valve. But at the time when the valve first starts to open this region would need to be filled with a mesh as it would not have a mesh initially since there would not be a fluid volume. The upstream region is an initially fixed volume of fluid which is evacuated through the valve during the simulation - the fluid is sucked out of the upstream region due to the specified decreasing downstream pressure. The only data known about the valve is its geometry and spring stiffness (constant). It is not known at any given time the amount that the valve will be open - that's part of the reason for doing the simulation. Everything I can find so far has 1) steady analysis of a valve that is open and does not move, 2) a valve displacement that is defined at given time points or 3) the valve is initially open (not initially closed) and its motion is driven by the fluid with a 1DoF solver. Thanks

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April 26, 2014, 07:32		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	It is tricky to model changes of state (ie closed to open). You might be able to get around it by starting with the valve open just a fraction - not enough to let a significant amount of flow through. Then the valve can open from there and you do not have to model the opening event. Alternatively you can use the domain interface conditional opening feature to crack something open. A further alternative is to use dynamic remeshing to handle the opening. It will take some careful planning to handle the new regions which appear as the valve opens.