[maka]

Hi!

How can I introduce a 2*Pi symbol in block mesh file?

Thanks.

[maka]

Here is some explanation:

usually in channel flow dimensions are specified in terms of Pi and delta. But Pi only shows itself in the periodic directions (x,z), which means we can not just added to convertToMeter as a scale and we have to introduce its in each point dimesion. This will require at least a 6 (may be more) digit accuracy in every x and z coordinate for all points.

One can enter it by hand but its a tiring process especially if you have multiple blocks. I there any way to introduce a symbole and a multiplication operator in blockMesh file.

ex: 2*Pi

Thanks.

[henry]

The best way we have found to do this is to use the m4 macro pre-processor inconjunction with gawk or perl to do the maths. Imply write a blockMeshDict.m4 as an input file to m4, run m4 on it and output the blockMeshDict for blockMesh. m4 allows you to define variable, evaluate expressions etc. etc., with a bit of effort it makes generating complex meshes with blockMesh much easier.

[eugene]

Or if you're not keen on m4 you can just use the transformPoints utility to scale all your x and z dimensions by Pi after you have run blockMesh.

[chris]

Perhaps incorporate PI into the converToMeters field of the blockMeshDict - it is just a fixed scaling:
http://www.opencfd.co.uk/openfoam/do...ml#dx31-165018

[eugene]

Another good idea would be to alter blockMesh to use a vector instead of a scalar scaling factor. That way you would be able to scale by PI in the x and z directions but not the y direction.

This is very easy to do. You need to alter 2 files:
blockMesh.H: line 65
change
scalar scale_
to
vector scale_

createPoints.C: line 62
change
] = scale_*blockPoints[blockPointLabel];
to
] = vector
(
scale_.x()*blockPoints[blockPointLabel].x(),
scale_.y()*blockPoints[blockPointLabel].y(),
scale_.z()*blockPoints[blockPointLabel].z(),
);

To accommodate this you need to modify your blockMeshDict:
convertToMeters <somenumber>;
convertToMeters (<num> <num> <num>);

Recompile and you are ready to go.

[billy]

Is there an example of using blockMeshDict.m4 to define variables in the current OpenFOAM release?

[eugene]

Here is an example of an m4 macro I used during my PhD. The foam formatting is probably out of date now, since I used it with Foam2.2.

If you get it working, please post the script to the Wiki so everyone can benefit from it.

meshDescription.m4

[billy]

Is it possible to use standard math functions such as sin and cos?

[maka]

vector scale_

I followed the steps for redefining scale_ as vector and compiled, sourced but when I run blockMesh I get the following message:

file: /home/maka/OpenFOAM/marwan-1.2/run/tutorials/icoFoam/cavity/constant/polyMesh/bl ockMeshDict::convertToMeters at line 26.

From function operator>>(Istream&, scalar&)
in file primitives/scalar/scalar.C at line 94.

it seems that there is convertToMeters is read at another location where we need to modify the defined input operator to:

operator>>(Istream&, vector&)

I did grep and found scale_ in :

blockMesh.C: scale_(readScalar(meshDescription.lookup("convertT oMeters")))

Should not readScalar be readVector?
can any body help?

Regards,
Maka

[maka]

compiler errors:

It turned out that, the compilation did not go well after I did the changes. Here is the message: any hint on what to do to make it work:

+ cd mesh
+ ./Allwmake
+ cd generation
+ ./Allwmake
+ wmake blockMesh
make: Nothing to be done for `allFiles'.
make: `Make/linuxGcc4Opt/dependencies' is up to date.

SOURCE_DIR=.
SOURCE=blockMesh.C ; g++ -m32 -Dlinux -Wall -W -Wno-unused-parameter -Wold-style-cast -O3 -ffast-math -DNoRepository -ftemplate-depth-30 -IcurvedEdges -I/home/marwan/OpenFOAM/OpenFOAM-1.2/src/meshTools/lnInclude -I/home/marwan/OpenFOAM/OpenFOAM-1.2/src/dynamicMesh/lnInclude -I/home/marwan/OpenFOAM/OpenFOAM-1.2/src/OpenFOAM/lnInclude -IlnInclude -I. -fPIC -pthread -c $SOURCE -o Make/linuxGcc4Opt/blockMesh.o
blockMesh.C: In constructor 'Foam::blockMesh::blockMesh(Foam::IOdictionary&)':
blockMesh.C:51: error: no matching function for call to 'Foam::Vector<foam::scalar>::Vector(Foam::scalar)'
/home/marwan/OpenFOAM/OpenFOAM-1.2/src/OpenFOAM/lnInclude/VectorI.H:79: note: candidates are: Foam::Vector<cmpt>::Vector(Foam::Istream&) [with Cmpt = Foam::scalar]
/home/marwan/OpenFOAM/OpenFOAM-1.2/src/OpenFOAM/lnInclude/VectorI.H:69: note: Foam::Vector<cmpt>::Vector(const Cmpt&, const Cmpt&) [with Cmpt = Foam::scalar]
/home/marwan/OpenFOAM/OpenFOAM-1.2/src/OpenFOAM/lnInclude/VectorI.H:59: note: Foam::Vector<cmpt>::Vector(const Cmpt&, const Cmpt&, const Cmpt&) [with Cmpt = Foam::scalar]
/home/marwan/OpenFOAM/OpenFOAM-1.2/src/OpenFOAM/lnInclude/VectorI.H:51: note: Foam::Vector<cmpt>::Vector(const Foam::VectorSpace<foam::vector<cmpt>, Cmpt, 3>&) [with Cmpt = Foam::scalar]
/home/marwan/OpenFOAM/OpenFOAM-1.2/src/OpenFOAM/lnInclude/VectorI.H:45: note: Foam::Vector<cmpt>::Vector() [with Cmpt = Foam::scalar]
/home/marwan/OpenFOAM/OpenFOAM-1.2/src/OpenFOAM/lnInclude/Vector.H:62: note: Foam::Vector<foam::scalar>::Vector(const Foam::Vector<foam::scalar>&)
make: *** [Make/linuxGcc4Opt/blockMesh.o] Error 1

Thanks,
Maka

[hjasak]

Yes: read the message, readi it carefully and then read it again:

blockMesh.C:51: error: no matching function for call to
'Foam::Vector::Vector(Foam::scalar)

It says: on line 51 of the file blockMesh.C you are attempting to create a vector out of a scalar.

Hope it is now clearer :-)

Hrv

[maka]

readVector,

I tried to replace readScalar by readVector I got the following error. Sorry if it looks easy but this is my first attempt to modify a file of the code.

blockMesh.C: In constructor 'Foam::blockMesh::blockMesh(Foam::IOdictionary&)':
blockMesh.C:46: error: 'readVector' was not declared in this scope

Thanks

[hjasak]

scale_(meshDescription.lookup("convertToMeters")),

[maka]

Thanks.

[andrewfedosov]

I use the Windows OpenFOAM 1.5. Can I run the .m4 file in order to construct a blockMeshDict file?

Maybe, someone can give a link to the tutorial for the m4 language (for instance, can I have if-statements in .m4 file)?

Thanks in advance