[supermgm]

Hello all,

I'm rarely a poster on forums, but this problem has caused me to stop being a lurker and become active for once!

Basically I'm a final year Uni student current undertaking an Automotive HVAC project regarding the hydraulic efficiency of the Blower Wheels used (Centrifugal Fan). I have run numerical solutions before on the placement I did, using Fluidnexus, AcuSolve and FieldView for all my simulations. However this year I'm using STAR.

The problem is surrounding getting my CATIA V5 geometry volume meshed. When I used Fluidnexus I would simply extract the inner volumes of the geometry in CATIA, ensuring the geometry was "clean" with separate regions defining the differing boundaries of parts. So within a typical scroll with a blower wheel (In CATIA) I would boolean remove a "dumb" outline of a wheel to get a non fluid zone where I would then align the wheel around an axis as a separate body in order to assign an MRF to that region.

However I seem to be getting confused with the processes needed in order to generate a volume mesh for a blower wheel and scroll in STAR, without errors. So my questions are:

1: Should I do any boolean removals of the wheel in the scroll in STAR and not CATIA?

2: Should I perform surface repairs to the geometry? (As this seems to cause wild manipulations to my surfaces)

3: Is there a good tutorial online regarding setting up the mesh of a centrifugal fan? (I've already done the MRF tutorial within STAR, however it doesn't show you how to set up the geometry!)

I apologise if this is a stupid question, but I have been pulling my hair out the last two days; and unfortunately my University isn't being particularly helpful...

Thanks in advance.

[me3840]

Originally Posted by supermgm

1: Should I do any boolean removals of the wheel in the scroll in STAR and not CATIA?

You can do it either way.

Originally Posted by supermgm

2: Should I perform surface repairs to the geometry? (As this seems to cause wild manipulations to my surfaces)

This question confuses me. You should repair the geometry if it requires repair. How does repairing it cause 'wild manipulations'? You're the one making the changes, what are you changing?

Originally Posted by supermgm

3: Is there a good tutorial online regarding setting up the mesh of a centrifugal fan? (I've already done the MRF tutorial within STAR, however it doesn't show you how to set up the geometry!)

Not that I'm aware of, but there are a lot of other tutorials that do have geometry in them.

[Roman]

Originally Posted by me3840

This question confuses me. You should repair the geometry if it requires repair. How does repairing it cause 'wild manipulations'? You're the one making the changes, what are you changing?

This smells "Automatic Surface repair tool" long way.


Who ever reads this, never, ever use it. You should always have full control and make changes and repairs your self. If you don't have control over your input you will not get predictable results.

[supermgm]

Originally Posted by Roman

This smells "Automatic Surface repair tool" long way.


Who ever reads this, never, ever use it. You should always have full control and make changes and repairs your self. If you don't have control over your input you will not get predictable results.

Thank you for clearing this up for me. In my naive state I thought this was "the thing to do" as some tutorials online have often referred to it.

In future I will look into manual control of geometry repairs.

[me3840]

Originally Posted by Roman

Who ever reads this, never, ever use it. You should always have full control and make changes and repairs your self. If you don't have control over your input you will not get predictable results.

So I will expand on this a bit. Automatic surface repair is very useful, but one has to know what it's for. In my opinion it was a poor choice to include it so prominently in surface repair.

Never, ever use automatic surface repair tool to fix errors in raw (STL) geometry. Unlike what its name suggests, this is not its purpose, and because of that fact it tends to make a mess out of everything.

However it is very useful for fixing minor errors in processed surface meshes i.e. delaunay triangulated surfaces. This is why auto surface repair is selectable as a mesher. Here it can fix messed up meshes that the surface remesher or a 3rd party mesher produces pretty easily.