# numbering in unstructured grid

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 March 5, 2003, 04:07 numbering in unstructured grid #1 reader Guest   Posts: n/a Hi, when we use a usual structured grid (for example, rectangles in a 2D case), each node (or cell) receives its "natural" number. The unstructured grid looks as a chaotic set of nodes. How it is necessary to number its nodes and cells? Thank. reader.

 March 5, 2003, 05:11 Re: numbering in unstructured grid #2 Madhukar M. Rao Guest   Posts: n/a Unstructured meshes will, usually, not show any "natural" numbering pattern. If you are writing a CFD solver for unstructured meshes, you will have to keep track of the neighbors for each cell, as well as its faces. Madhukar Rao ACRI

 March 5, 2003, 08:26 Re: numbering in unstructured grid #3 Praveen Guest   Posts: n/a When you generate an unstructured grid, the grid generator will number the nodes somehow. You may want to renumber them for efficient cache utilization. See R. Lohner: Applied CFD Techniques, Chapter 15

 March 5, 2003, 10:05 Re: numbering in unstructured grid #4 Nashat Guest   Posts: n/a Here are some references: R. Löhner - Some Useful Data Structures for the Generation of Unstructured Grids; Comm.Appl.Num.Meth. 4, 123-135 (1988). R. Löhner and M. Galle - Minimization of Indirect Addressing for Edge-Based Field Solvers; AIAA-02-0967 (2002). R. Löhner - Applied CFD Techniques; J. Wiley & Sons (2001). Regards,

 March 5, 2003, 10:36 Re: numbering in unstructured grid #5 Nashat Guest   Posts: n/a Lohner, Rainald, "Renumbering strategies for unstructured-grid solvers operating on shared-memory, cache-based parallel machines", Computer methods in applied mechanics and engineering, Elsevier, Vol 163, pp.95-109, 1998

 March 5, 2003, 11:36 Re: numbering in unstructured grid #6 xueying Guest   Posts: n/a I used GAMBIT to generate 10-node tetrahedral mesh. The node numbered well. Say, node 1,3,6,10 are always on the vertex, between 1 and 3 is always 2, between 1 and 6 is always 4, the others are the same.

 March 6, 2003, 03:23 Re: numbering in unstructured grid #7 Rami Guest   Posts: n/a When you generate an unstructured grid, an additional piece of information is required to supplement the node coordinates and numbers, namely a connectivity table. This table lists the node numbers of each cell (or element). For example, in 2D, if the quadrilateral cell No. k comprises of the corner nodes numbered { n1, n2, n3, n4 }, the connectivity table has { n1, n2, n3, n4 } as its k-th row (or coloumn). For structured grid this information is redundant, since each cell indices are related to its node indices. For example, in 2D, cell (i+1/2,j+1/2) comprises of the nodes { (i,j), (i+1,j), (i,j+1), (i+1,j+1) }.

 March 6, 2003, 14:14 Re: numbering in unstructured grid #8 Abhijit Tilak Guest   Posts: n/a Hi, The numbering of cells/nodes in unstructured grid goes beyond efficient memory utilization & reducing band width of the coefficient matrix. An fully explicit will work well with un-ordered mesh. If you want to implement implicit/Semi-Implicit scheme your mesh (cells) must be re-ordered. If you don't do this the scheme reverts to explicit.... since updated value may not be available. The scheme is then at mercy of CFL condition. I was not aware of this until, I had to write a unstructured grid code for simulatin incompressible viscous flows. Intrestingly this is not stated in the literature that I came across. Probably it is implied or too "trivial" to be stated. Abhijit

 March 6, 2003, 14:58 Re: numbering in unstructured grid #9 Nashat Guest   Posts: n/a Some more refernces which might be of interest: D. Sharov, H. Luo, J.D. Baum and R. Löhner - Implementation of Untructured Grid GMRES+LU-SGS Method on Shared-Memory, Cache-Based Parallel Computers; AIAA-00-0927 (2000). Sharov, D. and Nakahashi, K., "Reordering of Hybrid Unstructured Grids for Lower-Upper Symmetric Gauss-Seidel Computations," AIAA Journal, Vol. 36, No. 3, pp. 484-486, 1998. Regards

December 31, 2010, 01:07
numbering in unstructured grid
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 Originally Posted by Nashat ;23498 Here are some references: R. Löhner - Some Useful Data Structures for the Generation of Unstructured Grids; Comm.Appl.Num.Meth. 4, 123-135 (1988). R. Löhner and M. Galle - Minimization of Indirect Addressing for Edge-Based Field Solvers; AIAA-02-0967 (2002). R. Löhner - Applied CFD Techniques; J. Wiley & Sons (2001). Regards,
Hi, I am new to CFD programming. Can anybody explain or send the tutorial on the bin renumbering for 3-Diemension, as Prof. Lohner discussed in Applied CFD Techniques.

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