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Old   June 29, 2004, 17:41
Default Gambit & Propeller Meshing
  #1
James Date
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Hi Guys,

I'm trying to create a mesh around a propeller geometry (CAD defined), however, I'm not sure which is the best method to use:

1) Boolean subtraction of propeller geometry from say a cylinder volume.

2) Build blocks up around the propeller geometry.

Obviously option (1) is the easiest, however, I seem to have problems generating a tet-mesh in the volume created.

Option (2) is very time consuming but would result in better grid which is easier to control.

The propeller geometry is quite complex, but the surfaces are not overly skewed.

Has any one got an example block structure they could show me.

Regards James

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Old   July 3, 2004, 04:29
Default Re: Gambit & Propeller Meshing
  #2
Jörn Beilke
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You can spend a lot of time trying to mesh a propeller with gambit and end up unhappy with the result.Even if you are able to create a mesh, it won't be a good mesh.

I use Gridpro for this kind of jobs which gives me excellent meshes in a short time. If you dont't have a Gridpro near to you , you can also use icem hexa , which still produces reasonable results.

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Old   July 3, 2004, 07:36
Default Re: Gambit & Propeller Meshing
  #3
James Date
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Joern

Thanks for the advice mate. Yep, you're right Gambit is very poor a creating grids around propeller geometries. I approached it using a number of methods, the result is a far from perfect grid! The only way i can see that you can make a reasonable grid in Gambit around a propeller is to build lots of blocks around the geometry. This is very labour intensive! I'm now looking at other options.

Regards James

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Old   July 6, 2004, 06:35
Default Re: Gambit & Propeller Meshing
  #4
Jörn Beilke
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Dont't know if you got the mail.

There is an example now on:

http://www.beilke-cfd.de/blade_gridpro.nas.gz

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Old   July 6, 2004, 13:39
Default Re: Gambit & Propeller Meshing
  #5
James Date
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Hi

Thanks for sending me the link for the grid file for an example of a gridpro propeller mesh. I'm not quite sure how to read it as i'm unsure of the Grid format.

Regards James

P.S. Do you know why the Gridpro web site is not working?
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Old   July 6, 2004, 14:20
Default Re: Gambit & Propeller Meshing
  #6
Jörn Beilke
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It is in Nastran format. you can import it directly into fluent.

The Gridpro web site is working now.
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Old   July 6, 2004, 14:54
Default Re: Gambit & Propeller Meshing
  #7
James Date
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Hi

I just tried reading it into Fluent and it just crashed and it gave the following message.

************************************************** * Reading "| gunzip -c F:\blade_gridpro.nas.gz | tfilter fe2ram -cl -tNASTRAN -cl -d3"...

gunzip: F:\blade_gridpro.nas.gz: not in gzip format

NASTRAN file to RAMPANT file

Read 0 nodes, 0 elements, 0 groups.

Error: no nodes read from input. Error: couldn't filter input file.

Error: Floating point error: overflow

Error Object: ()

************************************************** *

Would it be better to read the geometry into gambit and then pass it to Fluent?

Regards

James
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Old   July 6, 2004, 16:54
Default Re: Gambit & Propeller Meshing
  #8
Jörn Beilke
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you have to unzip the file before reading. If you are a windows user you can use winzip or winrar for that purpose.

it is better to read it directly into fluent since the boundary regions are preserved this way. gambit trashes them usually.
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