Simcenter STAR-CCM+ Closing of a valve

If you find yourself modeling the closing of a valve using morphing you eventually reach the point where you want to close it completely. Morphing is great for the motion part but it doesn’t let you close the valve completely. To do that you can cheat a little by turning an interface into a baffle instead. With Simcenter STAR-CCM+ version 2310 you can finally do this without the use of java. This is possible thanks to the addition of Stages .
Unfortunately, the point when you want your internal interface to turn into a baffle interface is usually when the distance is small, and the velocity through it is therefore rather high. If you want to remove some of the chaos that comes from this abrupt change in boundary conditions, you can have an intermediate step where you turn the internal interface into a porous baffle. If your porous baffle starts with no resistance it behaves as an internal interface. You can then ramp up the porosity of this porous baffle until the point where it almost stops the fluid from passing and thus behaves as a baffle interface. At this point you turn your porous interface into a baffle interface and the fluid stops completely.
Attached to this article you’ll find a very simple case consisting of 3 boxes. 10kg/s of air goes into the left box and the right box has a pressure outlet. Between the 3 boxes are 2 interfaces. The air is modelled with ideal gas:

The  middle box starts out just as big as its neighbors but morphs into 1% of that as the simulation runs. Its height looks like this:

When the middle box gets small enough (or valve is close enough) we start the process of turning it into a baffle interface. I have chosen to start this process at 0.1m. The mass flow though the highlighted interface in the first picture looks as follows:

If you look closely, you’ll see that:

1. At 0.081s the mass flow starts to drop – the interface is now a porous one.
2. At 0.086s the mass flow goes completely to 0 kg/s and stays there – the interface is now a baffle interface.
3. At 0.114s the mass flow starts to increase – the interface is now a porous one
4. At 0.119s the interfaces turns back to an internal interface and stays there until 0.2s when the box is back to its starting height.

The pressure in the boxes look like this (left box in yellow and right box in red):

The entire simulation is driven by Simulation Operations :

In the picture above you can also see that Stages is being used and that the interface called “closeMe” is staged, indicated by the tiny flag.
You can also see that Time Scales is being used to control the different parts of the simulation:

Each of the 3 stages of the simulation requires different stopping criteria’s and for “changePorous” I also want to decrease the time step size.

Please find attached the simple test file that you can run in serial (it is 3000 cells). You run it using Simulation Operations: