mesh from ANSA to OpenFOAM
 

hi at all!
my problem is the following: i generated a mesh for my complex geometry with a CFD algorithm in ANSA (its a surface mesh). now i heard that i should create a big cube around my geometry to get a volume mesh and openfoam will cut everything outside of my model with blockMesh. is that correct? actually i'm don't really know how to realize to get from a mesh in ansa to a volume mesh in openfoam that can be calculated with.
additionally i'm not really sure at what point a define my boundary conditions... already in ansa or later in an openfoam file?

best greets!

Hi there.

If you have created a good surface mesh in ANSA, why not
create the Volume mesh also there, specify the boundary conditions
and output a complete case for OpenFOAM?

Which version of ANSA are you using?

hi! thanks for your reply. i think i'll go two ways to compare them!

1) defining just a surface mesh of triangles without improving it. just output as a STL and volume-meshing will be done by blockMesh and autoHexMesh respectively.

2) as you said: creating a surface mesh in ANSA, improve it (skewness <0.6 (FLUENT) - is that a good criteria?) followed by creating the layers and volume-mesh.

actually i'm not really sure how thick my boundary layer should be and where to use volumemeshing (just there where the fluid passes or everywhere in the geometry?). also i don't know how to specify the boundary conditions in ANSA. is it just be done by creating PIDs?

best wishes!!

PS: i use ANSA 13.0.3

edit: i found the way to specify boundary conditions. what should i choose for my inlet and my outlet? just "patches"?
and why isn't possible to define my walls? they are listed in the prop.manager but are not visible in my model like the other PIDs...

Hello again,

I suggest you have a look at tutorial
PIPE BEND – Case setup and morphing for OpenFOAM
accessed from Help - ANSA documentation index

You will see first how to start ANSA for CFD, important
so that you get all the correct settings by default
and then how to setup the boundary conditions for
inlet outlet and walls and setup and OpenFOAM case.

Hope this helps

thanks for your advice...i looked for the tutorial you mentioned but unfortunately it is written in gray letters so i cannot access... :( too bad

Hi,
ansa does have at least a OpenFOAM Menu-Deck as presentation by Beta CAE System shows!
They were a Conference Sponsor of http://opensourcecfd.com/conference2008/ 2008 and they had a booth at the conference http://www.opensourcecfd.com/confere...y/dsc_0101.jpg. I did not attend the conference but ansa supports OF!=>Read:
Advanced Pre-processing Solutions For OpenFOAM®
V. Skaperdas, S. Saltiel, C. Kolovos
Beta CAE Systems S.A., Greece
Slides 30-37 are OF-related but I do not know how much they charge for this functionalty?

elvis

Like every functionality or module in ANSA there is no additional charge.
They all come together as one.

thanks a lot for your help!
after a week working with ANSA i got a better understanding for the handling and now i think i'm able to create a volume-mesh and write an openfoam output file thanks to the missing cfd tutorial file i requested from ANSA support.

I am glad to know this!

how to setup boundary conditions in ANSA
 

Hi, could you share your experience on how to setup boundary conditions in ANSA?

Thanks
Houghston

Hello Houghston,

Are you already using ANSA or thinking of doing so?

I am asking in order to know if I can use ANSA terminology to explain.

In general though boundary conditions are specified through the property card for each property (zone) of your model.
You set the type (wall, patch, symmetry etc) and then the
flow values (say U fixed value, or p zero gradient etc)

You can also specify the solver controls (controlDict, fvSchemes, fvSolution etc) or use predefined ones.

Let me know if you have any specific questions.

Vangelis

Thanks
 

Vangelis,

Thanks for the information. I am learning ANSA now by going through the user guide.

Houghston

Houghston,

I suggest you also check out the CFD tutorials, under
Help>ANSA Documentation/Tutorials and Examples
There is one for OpenFOAM also.

You can also find the corresponding files in the installation directory.

Vangelis

Hi Vangelis,

I use ANSA and am quite familiar with it. I start learning OpenFoam and thought of creating my background mesh and geometry with ANSA. In order to use snappyHexMesh.

But it would be more easy if could create a mesh with ANSA, without the need to convert to OF format.

What I can do is create a solid mesh and read it out. It create 7 files in the polyMesh folder: boundary, cellZones, faces, faceZones, neighbor, owner and points. So it seems to work correctly.

But what I could not find out yet: How can I define boundaries? Within "Auxilleries" there is a button "Interfaces", but it asks for a patch and a shadow patch. I guess, this is to be used when connecting two seperate meshes.

Can anyone help me out? Thanks!

Hi Ay82,

The boundaries are defined from the ANSA Property List.
Each ANSA PID is one boundary.
If you edit the Property card you can see the OpenFOAM boundary Conditions

Hope this helps

Best regards

Vangelis

PS. I assume you start ANSA in CFD mode from the launcher so that all
settings are predefined for CFD work

Hi,

I will check if its opened in CFD mode but I guess it is. I can switch to openFoam environment so I guess, it is CFD mode.

Anyhow, I do create PID's for the inlet, outlet and wall. Then I apply it on shells. Alltogether, these shells create a volume, so I can create a solid mesh. The shells are released.

When I output the mesh, these BC's only appear in the boundary file:

FoamFile
{
version 2.0;
format ascii;
class polyBoundaryMesh;
location "";
object boundary;
}
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/

3
(
WALL
{
type wall;
startFace 4572;
nFaces 200;
}
INLET
{
type patch;
startFace 4772;
nFaces 25;
}
OUTLET
{
type patch;
startFace 4797;
nFaces 25;
}
)

I expect them to appear also in some of the other files, right?

I would also expect to define the BC's on the solidfacets of the solid mesh. Or do you define it on shells with nodes that are equal the corresponding node on the solid mesh?

If you start ANSA and you see the OpenFOAM icon at the top right next to Mesh Button then you are in CFD mode.

Indeed you specify the BCs on the shells. You do not need to assign them on the volume element facets.
ANSA will do all the rest correctly.

The BCs appear in boundary file
the exact boundary conditions will appear in /0/<variable file>

Ok, thats great! Thanks a lot!

I actually just want to create my mesh and do the rest with text editor.

fair enough!

you are welcome