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When rotating my blade-mesh, do I need to set a GGI between them?

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Old   March 22, 2014, 09:22
Default When rotating my blade-mesh, do I need to set a GGI between them?
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Hi!

We have made a blade geometry for a turbine using BladeGen, and made the mesh for the fluid zone around the blade in TurboGrid. To do a full scale simulation we of course want copy the mesh 10 times around to make a full runner. What is the best way to do this? Is it possible to do this in TurboGrid?

Right now, we simply rotate and copy the mesh 10 times in CFX-Pre. So between every rotated copy, there will be an interface. Do we need to set a GGI-interface bewteen every fluid zone around each blade? If we don't, will we get an error or maybe some information is lost?

I have tried looking for answers in tutorials but so far I've feel I haven't got an answer.
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Old   March 23, 2014, 05:22
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I am not familiar with Turbogrid so cannot say anything about what it can or cannot do.

But in CFX-Pre when you copy mesh sections like this you have the option of merging it with the existing mesh. This only works if the two meshes match EXACTLY on the interface. If done successfully you will not need an interface between the mesh sections as they are contiguous.

But if you cannot do this then the only way of connecting them is with GGI interfaces.

If you want to know what happens if you do not define a GGI on an interface when one is required - then why don't you try it and find out? It is pretty obvious what happens.
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Old   March 23, 2014, 10:45
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Quote:
Originally Posted by ghorrocks View Post
I am not familiar with Turbogrid so cannot say anything about what it can or cannot do.

But in CFX-Pre when you copy mesh sections like this you have the option of merging it with the existing mesh. This only works if the two meshes match EXACTLY on the interface. If done successfully you will not need an interface between the mesh sections as they are contiguous.

But if you cannot do this then the only way of connecting them is with GGI interfaces.

If you want to know what happens if you do not define a GGI on an interface when one is required - then why don't you try it and find out? It is pretty obvious what happens.
Thanks for taking the time.

I have tried it, and get reasonable numbers. But I wan't to know whether they are correct or not! I'm thinking that just because a get a result, doesn't mean it's correct (garbage in, garbage out) hehe.

If anybody else knows something about the subject, I'td be interesting to get an answer =)
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Old   March 23, 2014, 17:47
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Accuracy in CFD is a very important topic. This FAQ is a starting point:
http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F
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