Starting OF C++

sisetrun · June 30, 2016, 08:44

Hello everybody,

I would like to learn more about OF programming. I have some basic skills in C++ and python. So, I know that the mission is not that easy but somehow I have to start...

I had a look at the application/test. And that is where my problems already start: "How can I execute such a test case?"

I compiled the case with wmake, changed the Make/file with _USER_ and so on... But I have no clue executing the compiled file.

I am very thankful for every answer!

Thanks a lot,

Best regards

PS: Any additional info for getting used to programming OF is highly appreciated

sina_mech · June 30, 2016, 14:36

This should be helpful:

https://openfoamwiki.net/index.php/H...ure_to_icoFoam

rhythm · July 5, 2016, 06:44

Hi,

Compiling applications/solvers in OpenFOAM is not much different than in regular C++.

Compilation creates a binary file that can be run and in your Make/files you specify where that binary is going to be saved (in your case it's in $FOAM_USER_APPBIN which is a variable inside OpenFOAM environment). After compilation was successful, in your terminal you can type

Code:

ls $FOAM_USER_APPBIN

and you should see a new binary file for the application you've just compiled.

When apps/solvers are compiled into binaries with [i]wmake[/it] they are seen globally on your machine, so simply typing the name of the app/solver inside your terminal should work and it should be run.
Rarely, but sometimes right after compilation your terminal can be temperamental and doesn't see the application even though you can see it's binary file. So either open a new terminal window or type

Code:

rehash

and it should work.

As sina_mech has posted, openfoam wiki is a good starting place to become more familiar with how OpenFOAM framework works.

Hope this helps.
Ben

sisetrun · July 5, 2016, 07:01

Thanks Ben and sina_mech,

I already had a look at the wiki.
Until now, I did some C++ tutorials form youtube and read about C++ in books.
Do you know a tutorial/lecture where C++ is directly linked to OpenFoam examples?
I found some where solvers and applications are modified. But this seems quit complicated to start with.

Thanks so far,
best regards

rhythm · July 7, 2016, 12:23

Hi sisetrun,

Regarding books
You might want to check out 'OpenFOAM Primer' written by Jens Hopken and Tomislav Maric. They worked on it when they were learning to work with OF, so it was tailored for people trying to bridge the gap between CFD knowledge, C++ and how it is done in OF framework.

The link:
http://www.sourceflux.de/book/

Regarding CFD
You might like other CFD books, but you'd have to build that 'bridge' between maths and numerics to C++ and OF framework by yourself. There is an abundance of such books and imho they are all pretty much equivalent (some may be better than others, but in the end it will depend on personal preference). Quick google search will show you the options.

Regarding tutorials/lectures
- I liked the lecture notes from Chalmers University course on OpenFOAM and CFD. I can't remember if it is publicly available, but a quick email to the organisers will help you to find that out.
- At the moment I can't think of any other comprehensive course material publicly available. Having said that, from my experience the best thing is to have a specific question in mind and then see if there's an answer somewhere on the web, because most of the time someone either made a presentation/lecture/paper about it or discussed it here on the forum.

Another note, starting with OF can be a little bit daunting, due to the size of the code, but in my experience the best thing is to start reading the code and getting used to the structure and the way it's written. After some practice it becomes much more clearer as to how mathematics is put to code and then it really is as some people say 'Like playing lego with CFD building blocks'

Hope this helps.
Ben

Jerryfan · July 7, 2016, 14:50

Hi Sisetrun,

I also just started the learning process of this amazing code. I feel like I am gradually into it, although the way ahead is still very long. My suggestion is to install a debug mode version and try to debug the code. Also try to understand the structure of the code, especially the class inheritance relationships. I don't think there is a shortcut.

June 30, 2016, 08:44	Starting OF C++	#1
sisetrun Member Sebastian Trunk Join Date: Mar 2015 Location: Erlangen, Germany Posts: 60 Rep Power: 11	Hello everybody, I would like to learn more about OF programming. I have some basic skills in C++ and python. So, I know that the mission is not that easy but somehow I have to start... I had a look at the application/test. And that is where my problems already start: "How can I execute such a test case?" I compiled the case with wmake, changed the Make/file with _USER_ and so on... But I have no clue executing the compiled file. I am very thankful for every answer! Thanks a lot, Best regards PS: Any additional info for getting used to programming OF is highly appreciated

July 5, 2016, 06:44		#3
rhythm Member Ben Jankauskas Join Date: Jun 2013 Location: Exeter Posts: 34 Rep Power: 12	Hi, Compiling applications/solvers in OpenFOAM is not much different than in regular C++. Compilation creates a binary file that can be run and in your Make/files you specify where that binary is going to be saved (in your case it's in $FOAM_USER_APPBIN which is a variable inside OpenFOAM environment). After compilation was successful, in your terminal you can type Code: ls $FOAM_USER_APPBIN and you should see a new binary file for the application you've just compiled. When apps/solvers are compiled into binaries with [i]wmake[/it] they are seen globally on your machine, so simply typing the name of the app/solver inside your terminal should work and it should be run. Rarely, but sometimes right after compilation your terminal can be temperamental and doesn't see the application even though you can see it's binary file. So either open a new terminal window or type Code: rehash and it should work. As sina_mech has posted, openfoam wiki is a good starting place to become more familiar with how OpenFOAM framework works. Hope this helps. Ben

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June 30, 2016, 14:36		#2
sina_mech Senior Member SinaJ Join Date: Nov 2009 Posts: 136 Rep Power: 16	This should be helpful: https://openfoamwiki.net/index.php/H...ure_to_icoFoam

July 5, 2016, 07:01		#4
sisetrun Member Sebastian Trunk Join Date: Mar 2015 Location: Erlangen, Germany Posts: 60 Rep Power: 11	Thanks Ben and sina_mech, I already had a look at the wiki. Until now, I did some C++ tutorials form youtube and read about C++ in books. Do you know a tutorial/lecture where C++ is directly linked to OpenFoam examples? I found some where solvers and applications are modified. But this seems quit complicated to start with. Thanks so far, best regards

July 7, 2016, 12:23		#5
rhythm Member Ben Jankauskas Join Date: Jun 2013 Location: Exeter Posts: 34 Rep Power: 12	Hi sisetrun, Regarding books You might want to check out 'OpenFOAM Primer' written by Jens Hopken and Tomislav Maric. They worked on it when they were learning to work with OF, so it was tailored for people trying to bridge the gap between CFD knowledge, C++ and how it is done in OF framework. The link: http://www.sourceflux.de/book/ Regarding CFD You might like other CFD books, but you'd have to build that 'bridge' between maths and numerics to C++ and OF framework by yourself. There is an abundance of such books and imho they are all pretty much equivalent (some may be better than others, but in the end it will depend on personal preference). Quick google search will show you the options. Regarding tutorials/lectures - I liked the lecture notes from Chalmers University course on OpenFOAM and CFD. I can't remember if it is publicly available, but a quick email to the organisers will help you to find that out. - At the moment I can't think of any other comprehensive course material publicly available. Having said that, from my experience the best thing is to have a specific question in mind and then see if there's an answer somewhere on the web, because most of the time someone either made a presentation/lecture/paper about it or discussed it here on the forum. Another note, starting with OF can be a little bit daunting, due to the size of the code, but in my experience the best thing is to start reading the code and getting used to the structure and the way it's written. After some practice it becomes much more clearer as to how mathematics is put to code and then it really is as some people say 'Like playing lego with CFD building blocks' Hope this helps. Ben

July 7, 2016, 14:50		#6
Jerryfan Member Jerry Join Date: Oct 2013 Location: Salt Lake City, UT, USA Posts: 52 Rep Power: 12	Hi Sisetrun, I also just started the learning process of this amazing code. I feel like I am gradually into it, although the way ahead is still very long. My suggestion is to install a debug mode version and try to debug the code. Also try to understand the structure of the code, especially the class inheritance relationships. I don't think there is a shortcut.