Hi

I am trying to set up a periodic boundary between inlet and outlet of a pipe to get fully developed flow. I want to define pressure drop between inlet and outlet to drive the flow. How do I do that in STAR CCM? I have imported mesh from ICEM and this is LES simulation.

Use a user-defined field functions to define periodic pressure on your boundary...you can use time as variable to set up a pressure(t) in form of: A sin(2*pi*f*t)

Thank you for your answer. I do not need to impose time varying boundary at the inlet. I just want to run a simulation with cyclic boundary with pressure drop to drive the flow.

I was indeed trying to do the same thing but was told that its not possible in STAR CCM+. SO I that simulated the whole of the channel.

and what if you try to use a user-defined field functions to extract the scalar/vector quantity you want on one boundary and then copy that quantity on the other one?

Yes that can be done. But then the coordinate matching can be a problem. Going for the full model will have its own drawbacks like memory which I am facing.

Thank you for your answers guys. We can, however, set up periodic boundary in star ccm. We need to create an interface of inlet and outlet and specify pressure drop between the boundaries. If you are using segregated solver you would need to specify mass flow rate. See "Working with interfaces" in documentations.

I this periodicity exist in direction of flow?? What I got from your question was that you are willing to have periodicity in direction of flow. If this is correct than the defination of periodicity in STAR CCM+ is a bit different, I think. The flid flows in direction perpedicular to the periodic boundries. Please elaborate...

Yes I want to have periodicity in the direction of flow. I am using 3.06 version of Star CCM and I believe it has periodicity in the direction of flow. Thats why we sepcify mass flow rate or pressure drop to drive the flow.

I am having some problems with achieving convergence but I am fairly sure it has periodicity in the direction of flow.

Please can you elaborate how are you doing it?? Is it periodic or repeated flow? Thakns for help. Waseem

It is periodic. I highlighted inlet & outlet and right clicked on it to choose create interface & then periodic. It will create a new node called interfaces. You open that node click on periodic and choose fully developed as your option or what ever you want to choose. Under physics value set your pressure drop or mass flow rate.

I tried it but getting floating error. What does Pressure Jump or Mass flow rate under physics in interface, means??? Is it the pressure jump or mass flow rate, across the periodic segment or along whole of the channel.

You have to set up mass flow rate or pressure jump to drive the flow, how else would you have fluid flowing through your channel? Pressure jump is the pressure drop between inlet and out. I am not sure about mass flow rate, I think its across your domain. And you can specify it using rho*U*A. You should check it though, I am not sure. Let me know what you found out, and how it went.

Regards

Thanks for the help. But the problem is that my channel has constant wall temperature as boundary condition, which CCM+ cannot simulate for periodic conditions. The boundaries are required to be adiabatic. for reference in guideline of CCM+:

Introducing STAR-CCM+ > Setting up the Problem > Setting Types > Interface Types Reference > Fully-Developed Interface

/Waseem

If your density is changing you can not use periodic boundary. Look into mass source term option to make it fully developed. What exactly are you trying to simulate?

Regards

[PSY]

Continuing the discussion of periodic Conditions in star ccm,
Consider a simple straight pipe.
One end is inlet and other is outlet.

I need to develop periodic boundary conditions between Inlet and some say a plane at the centre of the pipe. But remember the central plane is not a boundary.

So it will be like flow comming from inlet will pass through the central plane simultaneously inducing the same flow pattern at inlet, But it would continue towards the outlet.

how do i do it....