Altering the mesh

alejo · February 16, 2006, 07:04

Hi all
I´m new openFoam user. I´m doing a very simple mesh and I read about using m4 for change the points by defining the points. It is possible to change the mesh by using equations in m4? How should I proceed?.
Thanks.
Alejandro

hemph · February 16, 2006, 07:21

Hi Alejandro
You can let perl do the calculations if you add the command
define(calc, [esyscmd(perl -e 'printf ($1)')])
in the header of your m4-file. You can then use the newly defined calculator by calling calc(expression)
example:
define(CX, calc(R*cos((PI/180)*45)))
would assign to CX, the x-value of a point at a distance R, with an angle of 45 degrees.
//Rasmus

alejo · February 16, 2006, 08:06

Thanks Rasmus,
I was trying to doit, but I have to say that it is the first time that I heard about m4, and less about m4 files. Im using kDevelop c/c++ to change set the mesh manually, and then the blockMesh utility. I do not understand how to use the m4 command. If u have some comment about I would appreciate it.
Thanks again.

hemph · February 16, 2006, 08:15

you have to be careful then, apparently m4 can take over your life...
(http://www.gnu.org/software/m4/manua...tro.html#Intro)
There is a section in the WIKI on how to use m4 to generate a blockMesh. Did you see it?
http://openfoamwiki.net/index.php/HowTo_blockMesh _with_m4

February 16, 2006, 07:04	Hi all I´m new openFoam user.	#1
alejo New Member Alejandro Arrieta Join Date: Mar 2009 Location: Dortmund, Dortmund, Germany Posts: 5 Rep Power: 17	Hi all I´m new openFoam user. I´m doing a very simple mesh and I read about using m4 for change the points by defining the points. It is possible to change the mesh by using equations in m4? How should I proceed?. Thanks. Alejandro

February 16, 2006, 07:21	Hi Alejandro You can let perl	#2
hemph Senior Member Rasmus Hemph Join Date: Mar 2009 Location: Sweden Posts: 108 Rep Power: 17	Hi Alejandro You can let perl do the calculations if you add the command define(calc, [esyscmd(perl -e 'printf ($1)')]) in the header of your m4-file. You can then use the newly defined calculator by calling calc(expression) example: *define(CX, calc(Rcos((PI/180)45)))* would assign to CX, the x-value of a point at a distance R, with an angle of 45 degrees. //Rasmus

February 16, 2006, 08:06	Thanks Rasmus, I was trying	#3
alejo New Member Alejandro Arrieta Join Date: Mar 2009 Location: Dortmund, Dortmund, Germany Posts: 5 Rep Power: 17	Thanks Rasmus, I was trying to doit, but I have to say that it is the first time that I heard about m4, and less about m4 files. Im using kDevelop c/c++ to change set the mesh manually, and then the blockMesh utility. I do not understand how to use the m4 command. If u have some comment about I would appreciate it. Thanks again.

February 16, 2006, 08:15	you have to be careful then, a	#4
hemph Senior Member Rasmus Hemph Join Date: Mar 2009 Location: Sweden Posts: 108 Rep Power: 17	you have to be careful then, apparently m4 can take over your life... (http://www.gnu.org/software/m4/manua...tro.html#Intro) There is a section in the WIKI on how to use m4 to generate a blockMesh. Did you see it? http://openfoamwiki.net/index.php/HowTo_blockMesh _with_m4

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