Single vs multi-block structured meshes

ntonkin · August 17, 2009, 12:43

Hello,

I'm learning Fluent by going through the manual and can't figure out exactly what the differences are between multi-block structured meshes and single-block meshes. How do I know when to use what? What are the advantages and disadvantages of both? Thanks for any help.

harishg · August 20, 2009, 15:21

Check the book on grid generation by Thompson, available online.

jchawner · August 22, 2009, 10:42

ntonkin:

First recognize that we're talking about structured grids where the 3D spatial domain of interest in XYZ coordinates is transformed into a rectangular computational domain of xi-eta-zeta coordinates. In other words, there's a mapping between an arbitrarily shaped spatial region and a parallelepiped (block) in computational space. That mapping may be very difficult or even impossible to achieve for complex shapes. Therefore, the multi-block strategy is used to first decompose the spatial domain of interest into more than one regions, each of which can be more easily mapped into an independent computational block. Just as the blocks are adjacent in physical space, they are also adjacent (connected) in computational space. However, the overall agglomeration of computational blocks may not be rectangular (i.e. they might be L-shaped or even more complex).

Sometimes there are practical reasons for using a multiblock strategy as when you have different materials or fluids that are easily identified by putting them in their own block, boundary condition assignment, or any of several other reasons including something as mundane as the requirements of your flow solver.

Hope this helps.

faudiS8 · October 28, 2009, 15:51

Hi
I'm student and try to learn grid generation for my course of CFD. but a question today made me confused.I thought that if i want to grid the area around an airfoil I've to make a domain made by a half circle around it and a rectangle in the continue to see the back effects.[I think it would better to know you that I work with gambit].and then make a multiblock domain consist of a half circle with deleted airfoil in it and one or two rectangle at the back so we can see a grid of C type,isn't it?
but today my friend who works with gambit from 1 year ago told me that he can make a single block domain with high quality grid. this made me confused....how?
does he define a special type of points (corner,side,etc)in the domain at the vertices in the domain?
thanks for your guide.

August 17, 2009, 12:43	Single vs multi-block structured meshes	#1
ntonkin New Member Nick Join Date: Aug 2009 Posts: 4 Rep Power: 16	Hello, I'm learning Fluent by going through the manual and can't figure out exactly what the differences are between multi-block structured meshes and single-block meshes. How do I know when to use what? What are the advantages and disadvantages of both? Thanks for any help.

August 22, 2009, 10:42		#3
jchawner Senior Member John Chawner Join Date: Mar 2009 Location: Fort Worth, Texas, USA Posts: 275 Rep Power: 18	ntonkin: First recognize that we're talking about structured grids where the 3D spatial domain of interest in XYZ coordinates is transformed into a rectangular computational domain of xi-eta-zeta coordinates. In other words, there's a mapping between an arbitrarily shaped spatial region and a parallelepiped (block) in computational space. That mapping may be very difficult or even impossible to achieve for complex shapes. Therefore, the multi-block strategy is used to first decompose the spatial domain of interest into more than one regions, each of which can be more easily mapped into an independent computational block. Just as the blocks are adjacent in physical space, they are also adjacent (connected) in computational space. However, the overall agglomeration of computational blocks may not be rectangular (i.e. they might be L-shaped or even more complex). Sometimes there are practical reasons for using a multiblock strategy as when you have different materials or fluids that are easily identified by putting them in their own block, boundary condition assignment, or any of several other reasons including something as mundane as the requirements of your flow solver. Hope this helps. granzer likes this. __________________ John Chawner / jrc@pointwise.com / www.pointwise.com Blog: http://blog.pointwise.com/ on Twitter: @jchawner

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August 20, 2009, 15:21		#2
harishg Senior Member N/A Join Date: Mar 2009 Posts: 189 Rep Power: 17	Check the book on grid generation by Thompson, available online.

October 28, 2009, 15:51		#4
faudiS8 New Member Fariborz Soroush Join Date: Oct 2009 Location: Tehran, Iran Posts: 14 Rep Power: 16	Hi I'm student and try to learn grid generation for my course of CFD. but a question today made me confused.I thought that if i want to grid the area around an airfoil I've to make a domain made by a half circle around it and a rectangle in the continue to see the back effects.[I think it would better to know you that I work with gambit].and then make a multiblock domain consist of a half circle with deleted airfoil in it and one or two rectangle at the back so we can see a grid of C type,isn't it? but today my friend who works with gambit from 1 year ago told me that he can make a single block domain with high quality grid. this made me confused....how? does he define a special type of points (corner,side,etc)in the domain at the vertices in the domain? thanks for your guide.