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SHABAH March 20, 2001 07:25

Problem in creating .geo file
 
When I used two blocks(2-D) to furnished the geometry, geo. File was created. But when I used three blocks to create this geometry after suitable structured meshing, on running analyses errors were displayed mentioning that apperantely inconsistent no of elements, nodes on the faces of the solids. Meshing is done by ensuring structured meshing .When I used the same mesh on two blocks there is no error at the time of running analyses and geo. File was created. How I can removed these errors so that I can use three blocks instead of two.The size of one block is very small as compared to others.

James Date March 20, 2001 08:27

Re: Problem in creating .geo file
 
Hi there, I think you might have failed to set the correct K direction on one or more of the blocks. It must always be set so it points in the third dimension (i.e. Z-Direction), when solving two-dimensional flows in CFX-4.3. This must always be done when you use the >>CFX4>>OPTION>>TWO DIMENSIONS command in the .fc file. Hope this helps.

James

Cath Noakes March 21, 2001 06:12

Re: Problem in creating .geo file
 
Hi,

I've had similar errors which were caused by an incorrect global tolerance. If your error message also says 'may need to equivalence more nodes', try changing the value of the tolerance.

Cath

Budi March 28, 2001 14:48

Re: Problem in creating .geo file
 
I agree with Cath, my tips is, Try increase your Global Tolerance step by step but keep it smaller than the smallest distance between two nodes in your model. This should cure the problem.

Please note, CFX-Build creates for every block/solid their own nodes. At the joining face between two solids, there are two nodes at every node point. In Analyse, "Equivalencing" should delete one of those nodes. This is done by deleting other nodes which is lying within the distance set up by global tolerance.

Right from the start, if you know what the smallest distance between two nodes in your model would be, set the global tolerance by 1 or 2 digits smaller than that. This should suffice and stick with it.

Cheers Budi

Drona April 17, 2001 06:59

Re: Problem in creating .geo file
 
Hi James,

I also use Build to create geometries. Could you please tell me how to define grid coordinate directions while creating the mesh?

i.e. how can you tell CFX-Build to put K in the direction of Z, for example?

Thanks

Li Xinfeng April 17, 2001 08:01

Re: Problem in creating .geo file
 
In cfx, The grids direction is define by cfx,and the longest is set to I, then J, and the shortest is set to the K, But I think there are not effect to your calculation. You only be able to modify the direction I,direction j,direction k.for example change the direction of I from one side to other side of line. I know the gridgen can do this thing u need.

Drona April 17, 2001 09:48

Re: Problem in creating .geo file
 
Hello,

Thanks. Yes, it doesn't affect the calculation, but sometimes can be useful to assign grid aligned initial guess. If you can get the grid coordinates as you want, then it's easy to assign grid aligned initial guess. My problem is a multiblock volute and the Build puts the grid direction randomly. So I can not use the grid aligned initial guess, I have to use cylindrical coordinates.

I hope I could make my point clear

Cheers

Drona

Li Xinfeng April 17, 2001 21:43

Re: Problem in creating .geo file
 
Perhaps you can use the Gridgen to do it.I know this software can do it and get CFX4's geo file.

SHABAH April 23, 2001 02:42

Re: Problem in creating .geo file
 
can we use the geometry created in Gridgen directly in cfx4. Gridgen can make .geo file ? can we import geometry from any other softare along with the meshing and other information required for the geo file ?


Li Xinfeng April 23, 2001 04:55

Re: Problem in creating .geo file
 
you said:can we use the geometry created in Gridgen directly in cfx4. The answer is OF COURSE. The gridgen can get the CFX4's geo file directly when you ouput a mesh file. But You can only import the iges file to gridgen. It's can do anything as the cfx-build .

Shabah April 24, 2001 06:45

Re: Problem in creating .geo file
 
Thankyou Li Xinfeng

Actually I want to make spherical geometry, but Iam facing difficulties in meshing.Because we need

four edges surfaces.To creat four edges surfaces is very difficult for spherical part of the body. I am using cartesian coordinates. Is there any thing like Zero connector in Gridgen ? in CFX_4

Li Xinfeng April 24, 2001 09:10

Re: Problem in creating .geo file
 
I don't understand what difficult you met. In my means,It's very easy to creat a spherical geometry in build. Could you told me some detail, perhaps I will find what difficult you met.

Shabah April 25, 2001 01:02

Re: Problem in creating .geo file
 
When I create the hemi- spherical part of the geometry by revolving the curve to make a surface. The surface produced have three edges. When I go for the meshing , it give the message that the meshing will not be structured on that surface. I am using CFX-4, so I use the Isomesh option not the Paver

Li Xinfeng April 25, 2001 02:22

Re: Problem in creating .geo file
 
I have found the question. you can't do the hemi- spherical as that. 1, do what as you do. 2, project a small surface to the delete the hemi- spherical surface you do before. , so you will find there are have four line in the hemi- spherical surface. 3, break the curve of the bottom of the hemi- spherical to four part. 4, connect the point of the small surface with the point of the bottom line. 5, delete the hemi- spherical surface you do before. so you will found you get some lines and be able to creat six surfaces and every surface have 4 edges(five parts of the hemi- spherical and a bottom surface).but that is not end. 6, do a half of cube in the spherical and use surfaces of cube to make a solid with a part surface of the hemi- sphericals, you will get six solids. 7, then you will get a good O-gird. I hope it's clearly enough.


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