first steps and many questions

rollmops94 · October 2, 2017, 11:39

Hi,
my name is Jonas and I started using OpenFOAM 4 weeks ago.
I tried some tutorials succesfully, but there are many questions left.

Before using OpenFOAM, i used CFD Motion from Autodesk. It was very simple to create the mesh and start the simulation. With OpenFOAM i have many problems to create the mesh and start the simulation.
I want to simulate the airflow arround a formula 1 front wing. For this I want to create an wind tunnel within the wing. I used Salome Meca to create the wind tunnel and put the wing geometrie inside. I am not sure if everything worked by creating the mesh, but lets say that everything is fine. What are the next steps? I saw in youtube, that everyone copies the folders from the tutorials and changes a bit to start their simulation. But is there no possibility to create all files by myself? Or is there a program witch helps me by creating these?

And I don´t understand if I have to use snappyHexMesh or something else to work with my created Mesh (from Salome). Should I only copie this file (.unv) into my run folder? Or what are the steps after creating the .unv file?

Can anyone please tell me exactly all steps from creating the mesh to start the simulation? Or can you give my some tipps where i can find all these information?

Jonas

windscion · October 4, 2017, 15:34

There are no utilities to create jobs. You have to earn the ability to use OpenFOAM! (I think the entry barrier is intended to drive attendance at training courses.) UserGuide chapter 4 does cover the basics of directory structure, and Chapter 5 the basics of meshing.

What makes the tutorials so unhelpful is the fact that they typically lack the mesh files until you execute ./Autorun (which in turn usually calls blockMesh, not snappyHexMesh). In any case running ./Autorun and looking in constant/polyMesh/ should show you the files which define the mesh.

If you do not have a utility to convert to OpenFOAM, consider using a mesh tool which can export as OpenFOAM or for which you have a tool to convert to OpenFOAM.

Always run checkMesh to verify the mesh, especially when converted from another mesh format.

You need to choose a solver, by which I mean here an executable to run the simulation. There are lots of those under applications/solvers/ in your OpenFOAM install directory. (Do not confuse this with the solvers listed in system/fvSolution which are used to solve PDEs for the velocity, pressure, or other calculated terms.) Different solvers require different fields defined under the 0/ directory. Also, some have specified requirements for properties in files under the constant/ directory. Also, (such fun!) the names of various files depend upon the version of OpenFOAM you are using.

Then you need to magically divine a good choice for dt, use decomposePar to to set up a parallel run (assuming you want to finish this decade) and use something like

% mpiexec -np # name_of_solver -parallel

to run the simulation.

Then use reconstructPar to consolidate the results in one place and use your favorite post-processing utility to view the results.

October 2, 2017, 11:39	first steps and many questions	#1
rollmops94 New Member Jonas Join Date: Oct 2017 Posts: 4 Rep Power: 9	Hi, my name is Jonas and I started using OpenFOAM 4 weeks ago. I tried some tutorials succesfully, but there are many questions left. Before using OpenFOAM, i used CFD Motion from Autodesk. It was very simple to create the mesh and start the simulation. With OpenFOAM i have many problems to create the mesh and start the simulation. I want to simulate the airflow arround a formula 1 front wing. For this I want to create an wind tunnel within the wing. I used Salome Meca to create the wind tunnel and put the wing geometrie inside. I am not sure if everything worked by creating the mesh, but lets say that everything is fine. What are the next steps? I saw in youtube, that everyone copies the folders from the tutorials and changes a bit to start their simulation. But is there no possibility to create all files by myself? Or is there a program witch helps me by creating these? And I don´t understand if I have to use snappyHexMesh or something else to work with my created Mesh (from Salome). Should I only copie this file (.unv) into my run folder? Or what are the steps after creating the .unv file? Can anyone please tell me exactly all steps from creating the mesh to start the simulation? Or can you give my some tipps where i can find all these information? Jonas

October 4, 2017, 15:34		#2
windscion New Member Thomas Evans Join Date: Dec 2015 Posts: 21 Rep Power: 10	There are no utilities to create jobs. You have to earn the ability to use OpenFOAM! (I think the entry barrier is intended to drive attendance at training courses.) UserGuide chapter 4 does cover the basics of directory structure, and Chapter 5 the basics of meshing. What makes the tutorials so unhelpful is the fact that they typically lack the mesh files until you execute ./Autorun (which in turn usually calls blockMesh, not snappyHexMesh). In any case running ./Autorun and looking in constant/polyMesh/ should show you the files which define the mesh. If you do not have a utility to convert to OpenFOAM, consider using a mesh tool which can export as OpenFOAM or for which you have a tool to convert to OpenFOAM. Always run checkMesh to verify the mesh, especially when converted from another mesh format. You need to choose a solver, by which I mean here an executable to run the simulation. There are lots of those under applications/solvers/ in your OpenFOAM install directory. (Do not confuse this with the solvers listed in system/fvSolution which are used to solve PDEs for the velocity, pressure, or other calculated terms.) Different solvers require different fields defined under the 0/ directory. Also, some have specified requirements for properties in files under the constant/ directory. Also, (such fun!) the names of various files depend upon the version of OpenFOAM you are using. Then you need to magically divine a good choice for dt, use decomposePar to to set up a parallel run (assuming you want to finish this decade) and use something like % mpiexec -np # name_of_solver -parallel to run the simulation. Then use reconstructPar to consolidate the results in one place and use your favorite post-processing utility to view the results.