Difference between structured & unstructured mesh

 Register Blogs Members List Search Today's Posts Mark Forums Read

 February 18, 2003, 23:19 Difference between structured & unstructured mesh #1 Andrew Guest   Posts: n/a Hello everybody What's the difference between structured mesh and unstructred mesh? Thanks. Andrew

 February 23, 2003, 22:12 Re: Difference between structured & unstructured m #2 derrek Guest   Posts: n/a Andrew: Typically a structured mesh is comprised of hex (brick)elements (quads in 2D) that follow a unifrom pattern. An unstructured mesh does not follow a unifrom pattern, usually comprised of tet elements (tris in 2D). derrek vivekv8, MANOJ SS, Jason huang and 1 others like this.

 February 24, 2003, 10:39 Re: Difference between structured & unstructured m #3 Robin Guest   Posts: n/a Hi Andrew, A single block structured mesh may comprise of square elements (2D) or hexahedral elements (3D) which are orthogonal in i, j space (2D) or i, j, k space (3D). Although is is also possible to have wedges (3D), triangles (2D) and pyramids (3D) in a structured mesh. Looking at a 2D example, for simplicity, every node in a 2D structured mesh has a corresponding integer i and j index value which is unique. The physical locations of the nodes are stored in a table or are functionally related to the mesh space (ie (x,y)= f(i,j)). It is also implied then that the neigbours of node (i,j) are (i-1,j), (i+1,j), (i,j-1), (i,j+1), (i-1,j-1), and (i+1,j+1). If you are writing a CFD code, a structured mesh makes it very easy to loop through neighbours and can be efficient with memory. A structured mesh has many coding advantages, but it may be difficult to conform a single block to a complicated shape. Code developers have got around this by allowing multiple blocks (multiblock unstructured), but this can make the internal memory strucutres more inefficient. Another way to make the mesh generation simpler, and improve code performance in other ways is to throw away the block structure and replace indices with node numbers and a connectivity table. This is known as an unstructured mesh, because it lacks the i,j,k structure. A common misperception is that a hex mesh is strucutred and a tet mesh is unstructured. It is accurate to say that a tet mesh is unstructured, however a hex mesh can also be unstructred. The difference between a structured hex mesh and an ustructured hex mesh is simply in how the data is stored. Regards, Robin airfoil, therockyy, heidar and 20 others like this.

 February 27, 2003, 21:38 Re: Difference between structured & unstructured m #4 derrek Guest   Posts: n/a Robin: Thanks for the thorough explanation. I should have used the word "typically" a little more forcefully. I didn't mean to imply a definition of structured & unstructured. derrek

 January 3, 2012, 02:44 Structured HexaMesh and Unstructured Hexamesh Different #5 New Member   Jaiganesh S Join Date: Dec 2011 Posts: 8 Rep Power: 6 1.What is the main different between in structured hexa and unstructured hexa?

 January 8, 2012, 20:30 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,638 Rep Power: 98 Structured hex meshes are in a grid, so an element can be identified by and ijk coordinate. Unstructured hex meshes are, well, unstructured.

 February 2, 2012, 17:34 good news #7 Member   heidar jafarizadeh Join Date: Mar 2010 Location: Iran- Tehran Posts: 43 Rep Power: 8 hey guys In fact a mesh is said to be structured if one can found a primitive motif which is regular in space. This implies that for instance node connectivities has a fixed pattern. But the geometry may be not constant, for instance your mesh can be deformed from place to place (for instance to match a specific boundary). The only thing you know for sure when the mesh is regular is that the node (or elements) connectivty is always the same. This may be useful for algorithm design since you always have the same pattern. However unstructured mesh are generally more flexible, since the connectivity pattern is not fixed, at the cost of having to store the connectivity. There is no generic answer to your last question, since it depends strongly upon the application you have in mind. __________________ Best Regards Heidar Jafarizadeh

 April 2, 2014, 10:41 #8 New Member   Masoud Join Date: Feb 2014 Posts: 21 Rep Power: 4 Could you please explain it more? regards

 April 2, 2014, 18:20 #9 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,638 Rep Power: 98 This topic is covered in any CFD text book. I do not fancy retyping text books into forums.

March 21, 2016, 12:16
#10
Member

Join Date: Jul 2012
Posts: 45
Rep Power: 6
Quote:
 Originally Posted by ghorrocks This topic is covered in any CFD text book. I do not fancy retyping text books into forums.
I hope you realize we dont want a retyped Text explanation...
Something like this (quoted below - post by Robin) is much better than that..I'd call that condensed understanding ... and that's what guys mean while asking such questions .. they wish to save some time and effort by learning from a well learned fellow..!
Quote:
 Originally Posted by Robin ;65829 Hi Andrew, A single block structured mesh may comprise of square elements (2D) or hexahedral elements (3D) which are orthogonal in i, j space (2D) or i, j, k space (3D). Although is is also possible to have wedges (3D), triangles (2D) and pyramids (3D) in a structured mesh. Looking at a 2D example, for simplicity, every node in a 2D structured mesh has a corresponding integer i and j index value which is unique. The physical locations of the nodes are stored in a table or are functionally related to the mesh space (ie (x,y)= f(i,j)). It is also implied then that the neigbours of node (i,j) are (i-1,j), (i+1,j), (i,j-1), (i,j+1), (i-1,j-1), and (i+1,j+1). If you are writing a CFD code, a structured mesh makes it very easy to loop through neighbours and can be efficient with memory. A structured mesh has many coding advantages, but it may be difficult to conform a single block to a complicated shape. Code developers have got around this by allowing multiple blocks (multiblock unstructured), but this can make the internal memory strucutres more inefficient. Another way to make the mesh generation simpler, and improve code performance in other ways is to throw away the block structure and replace indices with node numbers and a connectivity table. This is known as an unstructured mesh, because it lacks the i,j,k structure. A common misperception is that a hex mesh is strucutred and a tet mesh is unstructured. It is accurate to say that a tet mesh is unstructured, however a hex mesh can also be unstructred. The difference between a structured hex mesh and an ustructured hex mesh is simply in how the data is stored. Regards, Robin

Super clear explanation btw Robin

 March 21, 2016, 18:07 #11 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,638 Rep Power: 98 Yes, Robin's answer was good and he should be commended for that. But vague questions like "Could you please explain it more?" really don't encourage people to write thoughtful answers as there was little thought put into the question. You will find that to get good answers you need to ask good questions - which means clearly stating what bit you don't understand and explaining what background reading/knowledge you have in the topic. Zaphod'sSecondHead likes this.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post aeroslacker Open Source Meshers: Gmsh, Netgen, CGNS, ... 12 January 19, 2012 04:52 kawamatt2 ANSYS Meshing & Geometry 17 December 20, 2011 12:45 Joe CFX 2 March 26, 2007 18:10 Althea FLUENT 21 February 6, 2001 08:05 Mignard FLUENT 2 March 22, 2000 06:12

All times are GMT -4. The time now is 07:57.