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Old   October 31, 2006, 16:51
Default Grids
  #1
Confused
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I have seen the terminology O-grid c-grid etc..Can someone explain what does each of those letters represent.I'm not sure what to exactly look for to know what they mean.

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Old   November 1, 2006, 05:07
Default Re: Grids
  #2
michael k
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O-grids and C-grids are special variants of blockstructured grids. For example if you want to mesh a circular duct you'll get a very bad grid when you are using only one block, because the CV's at the walls will be skewed... In this case you can use a O-grid which means that you have one block in the middle an four blocks that surround this block. So that you'll get this block structure:

_________ |\ /| | \___/ | | |___| | | / \ | |/_____\|

And a C-grid would be something like this (only upper half):

__________________ |\ | | \ | | \ | | \_____________| | | | | | | | |

Sorry for my poor English

Michae

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Old   November 1, 2006, 05:08
Default Scetch didn't work... *NM*
  #3
michael k
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Old   November 1, 2006, 09:04
Default Re: Grids
  #4
myron
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See this for an O-Grid:

http://www.ansys.com/products/icemcf...hexa/ogrid.htm

A C-Grid would be with one side of the 'O' removed.
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Old   November 2, 2006, 11:00
Default Re: Grids
  #5
Mani
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myron, that looks like a bad example. There is a small O-grid embedded in the animation, but if you don't know what to look for you won't be able to see that... and you cannot make a C-grid by cutting away half of an O-grid! A C-grid has a differently connected topology. Figure 4 on this website shows a C-grid.

http://www.aerodyn.org/CFD/Grid/examples.html
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Old   November 3, 2006, 01:23
Default Re: Grids
  #6
Charles
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Something to remember with multi-block structured grids, is that the concept of a grid being of O, C or H topology is a bit notional. It is a good description when you mesh with a tool like Icem Hexa, where you can start with a single block topology, which is then split in various ways to match to the geometry. If you are building a grid from the bottom up, i.e. you assemble blocks, it will tend to end up as a topology which can not be characterised as easily.
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Old   November 3, 2006, 08:17
Default Re: Grids
  #7
Mani
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...because the O-C-H nomenclature predates the time when multiblock techniques became popular. They are the main topologies for 2-D single-block grids over simple geometries such as airfoils.
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