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-   -   how to do a good meshing using unstructured mesh (http://www.cfd-online.com/Forums/fluent/31913-how-do-good-meshing-using-unstructured-mesh.html)

nikita August 1, 2003 00:20

how to do a good meshing using unstructured mesh
 
hello friends,,it seems that i have a problem in meshing since my grid check is always failed.my model is an aircraft which the flow around it..what is the good meshing, i mean what kind of size of meshing that is suitable for my model size:625mm..pls advise

Andrew Garrard August 1, 2003 06:03

Re: how to do a good meshing using unstructured me
 
There are several answers to your question. Here are some of them:

Create a grid who's density is smaller than the smallest flow structures you wish to capture.

Start with a coarse grid and use the FLUENT adapt function to resolve in area of high variable gradient. Although care is needed to ensure the grid is not too coarse to not pick up high variable gradients in the first place and so will have do data to adapt to.

Conduct a grid independance study. This is where you run a simulation with a coarse grid, then refine the grid and run the same simulation and examine the differance in the results. Continue to do this until the results do not alter with incrasing grid density. At this point the simulation is said to be "grid idependant"

nikita August 1, 2003 06:19

Re: how to do a good meshing using unstructured me
 
tq andrew for your good explaination.i just do what u have suggested.but i stil have a problem, i create 2 domains in order to minimise the element number in grid..but then, when i mesh the big domain after i mesh the small domain, the check grid is always failed.If i just mesh small domain, then check grid is done....why then??pls advise

Andrew Garrard August 1, 2003 07:57

Re: how to do a good meshing using unstructured me
 
I am not sure why your grid check is failing. What criteria is it failing on? If the grids are the same, it should not matter which is meshed first as this data is not exported to fluent from gambit.

nikita August 2, 2003 02:45

Re: how to do a good meshing using unstructured me
 
check grid failed because of non-positive face area exist...how to overcome this since i redo meshing many times..but then..the same warning still appear..pls advise

lou zhengquan August 13, 2003 03:04

Re: how to do a good meshing using unstructured me
 
there is a website, a tutorial of airfoil. maybe useful to you.

http://instruct1.cit.cornell.edu/cou...foil/step1.htm

Jim Clancy August 22, 2003 21:06

Re: how to do a good meshing using unstructured me
 
Nikita,

If you still have problem just send me the geometry file ( iges, step or parasolid ) and I will try to mesh it and tell you where is the problem.

Jim


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