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-   -   Arc sometimes ignored (http://www.cfd-online.com/Forums/openfoam/74714-arc-sometimes-ignored.html)

Wedge April 7, 2010 04:46

Arc sometimes ignored
 
Hi,

I am quite new to Openfoam and I have a few question that I wasn't able to answer so far.
My first problem is concerning a piece of pipe. It is supposed to look like a quarter of a pipe or a quarter of a cake but it doesnt. The "arc" is just neglected.
This happens when I try to connect the points 0 - 1 and 3 - 4.
Other points are connected with arc if I try. Just those two ones I need aren't.
I know that it is a very bad way of producing a grid for such a case (better would be o ring or wedge, ...) but it just bugs me that it still doesn't work even so it should!?
In another thread someone wrote that the grid would be quite screwed but blockMesh shouldn't care about that fact.

Hopefully someone can help!

Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                |                                                |
| \\      /  F ield        | OpenFOAM: The Open Source CFD Toolbox          |
|  \\    /  O peration    | Version:  1.5                                  |
|  \\  /    A nd          | Web:      http://www.OpenFOAM.org              |
|    \\/    M anipulation  |                                                |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version    2.0;
    format      ascii;
    class      dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
convertToMeters 0.001;
 
vertices
(
    ( -200.00  300    0)              //  0
    ( -200.00  0  300)                //  1
    ( -200.00    0.00    0.00)      //  2
    (    0.00  300    0)                //  3
    (    0.00  0  300)                //  4
    (    0.00    0.00    0.00)      //  5
);
 

edges
(
arc 0 1 (-200 212.13 212.13)
arc 3 4 (0 212.13 212.13)
);
 

blocks         
(
    hex (5 2 1 4 3 0 0 3) (15 20 1) simpleGrading (1 0.1 1)
);

patches
(
);
 
mergePatchPairs
(
);
 
// ************************************************************************* //


RBJ April 14, 2010 05:57

You are trying to make a kind of wedge mesh with circular top right?
How did you define your boundary conditions?

They should be wedge @ 2 5 3 0 & 2 1 4 5 (not necessarily in the right direction)

Why do you choose your local x-axis in negative x-direction?

bunni May 27, 2010 13:37

one thing
 
One obvious thing that strikes me is that you're trying to make an arc between pts 3 & 4. it should be curved in the z-direction, but you've only allowed for 1 section (the 3 numbers you type in after the hex definition. Try something like hex (....)(20 20 20). That'll give you 20 sections to make your curve.


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