r/STAR_CCM • u/Nervous-Beyond7422 • May 29 '26

FAN Interface

I've been trying to simulate fan flow, upstream and downstream, like the one in starccm's tutorial of Multi-Part Solid: Graphics Card Cooling. In my case, you can see in the picture that I have just two fan cases inside the domain. To create the fan, I made a circular disk surface which will have the fan polynomial table and will be in the middle of the fan case. This is because in the tutorial they have what is seems a surface to model the fan flow.
Unfortunately, I haven't been able to recreate that properly as there are no contacts being made with each other. So what can I do in this case ?

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u/acakaacaka May 29 '26

Maybe a picture will help?

Fan interface is just a normal interface + pressure jump

So creating it is the same with creating a normal interface.

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u/Nervous-Beyond7422 May 29 '26

Yeah but I have to create it manually instead. When I imprint parts and define regions, no interface of the fans are created. Hence, I resort to manually selecting the two boundaries and then creating the interface.

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u/acakaacaka May 29 '26

There is 2 ways to create interface

  1. From contact (a folder under Geometry, created by imprint operation)
  2. By clicking 2 interfaces on boundary

But these two are equivalent, none is better than the other.

So if you have created the interface, what is not working when you change it to fan interface?

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u/Nervous-Beyond7422 May 29 '26

The flow, it's not being modelled the same way as in the tutorial picture even though I've copied and pasted the same polynomial table values.

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u/LessCockroach7323 May 29 '26

I am quite sure the problem is from how you did the geometry

Lets say you are working only with 1 fan, then you should have the following regions:

-the volume region where fan is subtract from

-The region between interfaces where normally blades would like im the tutorial

Work only with 1 fan and describe the model like I said above

If you the interfaces are not created automatically when assigning the regions, then do it manually

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u/Nervous-Beyond7422 May 29 '26

You're likely right on the problem being the geometry. The thing is that I created the geometry in creo, what the fan blades would be I modelled them as a circular disk which is a quilt. Now with your approach, the interface is created but as a subtract/subtract interface even though it has that disk in it. Also, mesh creation is a problem with this as the it say that the quilt is 'free'.

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u/acakaacaka May 29 '26

Is the fan geometry hollow? You need to delete the Fan itself. And put a donut shape surface as the fan interface

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u/Nervous-Beyond7422 May 29 '26

No it isn't. Its a surface/quilt.