CFD for dummies

Fruit · May 6, 2013, 16:27

Hello

Is there a simple CFD system? I mean really simple. By the way it should be free.

In fact, I'm not entirely new to CFD. When studied in university I even wrote a very simple 2D NS-solver for laminar flows (theoretically, for turbulent too, but it was a direct solver using an explicit scheme so you can estimate time needed to solve a problem with Re far from 1). But I didn't go any deeper and haven't been working with CFD for a long time. I often can't understand if simulation aborted due to wrong CFL number, relaxation factors (I even can hardly recollect what do these magic words mean), erroneous boundary conditions or bad mesh.

At the moment I'm designing a fiction supersonic aircraft. I do it just for fun. But I want to make an airplane which looks like an airplane able to fly - there are many pictures made by artists without any limitations representing aircrafts with absurd, impossible forms. I don't want to make another flying saucer or X-wing. So I want to test my aircraft in some CDF system.

First I tried FlowVision. It's a Russian system with Russian documentation and so as I'm Russian myself, I tried it. All was good until I proceeded from tutorials to real problems. There was no person who could help me to find a mistake. In addition demo version of FV is limited by 15000 cells so I turned to other software. OpenFLOW seemed to be a good choice even though it was for *nix systems but it's too complicated. I can learn new meshing software, OpenFOAM config files and ParaView and I will do it if there will be no other choice but I want something easier. I tried Caedium and it was good. But when I replaced a sphere with a cone it started generate bad mesh. And yes, it's only trial. I found information about some NASA solvers but they are only for americans. I found SU^2 but, again, it needs external meshing tool and postproc...

So. As far as I understood, it is only a miracle that can help me to find easy software. Maybe someone of you is a wizard's friend? If not, would you please give me some advice about what combination of tools to choose? Which is simpler to learn, OpenFOAM with its standard tools or SU^2 (with which mesher)? Or maybe there is another combination "preproc - solver - postproc" which is simpler than either OpenFOAM or SU^2?

JR22 · May 6, 2013, 16:34

You can try OpenFoam via Helyx-OS (GUI tool). That's a good entry point. Once you grow out of Helyx-OS, you can start diving deeper into OpenFoam. The one caveat is that you have to install it in Linux (preferably Ubuntu 12.04). I installed it inside a Virtual Box and works well. After you get it installed, here is a video that runs you through an external aerodynamics simulation:
http://www.youtube.com/watch?v=yJbFnFzDLqo

Martin Hegedus · May 7, 2013, 01:55

OpenFOAM is not a coupled solver therefore it will not converge for transonic steady state solutions. Someone can correct me if I'm wrong. You'll need to focus on SU2 or Overture, http://www.overtureframework.org/.

Edit: I'm not sure if Overture implements turbulence models.

May 6, 2013, 16:27	CFD for dummies	#1
Fruit New Member Join Date: May 2013 Posts: 1 Rep Power: 0	Hello Is there a simple CFD system? I mean really simple. By the way it should be free. In fact, I'm not entirely new to CFD. When studied in university I even wrote a very simple 2D NS-solver for laminar flows (theoretically, for turbulent too, but it was a direct solver using an explicit scheme so you can estimate time needed to solve a problem with Re far from 1). But I didn't go any deeper and haven't been working with CFD for a long time. I often can't understand if simulation aborted due to wrong CFL number, relaxation factors (I even can hardly recollect what do these magic words mean), erroneous boundary conditions or bad mesh. At the moment I'm designing a fiction supersonic aircraft. I do it just for fun. But I want to make an airplane which looks like an airplane able to fly - there are many pictures made by artists without any limitations representing aircrafts with absurd, impossible forms. I don't want to make another flying saucer or X-wing. So I want to test my aircraft in some CDF system. First I tried FlowVision. It's a Russian system with Russian documentation and so as I'm Russian myself, I tried it. All was good until I proceeded from tutorials to real problems. There was no person who could help me to find a mistake. In addition demo version of FV is limited by 15000 cells so I turned to other software. OpenFLOW seemed to be a good choice even though it was for *nix systems but it's too complicated. I can learn new meshing software, OpenFOAM config files and ParaView and I will do it if there will be no other choice but I want something easier. I tried Caedium and it was good. But when I replaced a sphere with a cone it started generate bad mesh. And yes, it's only trial. I found information about some NASA solvers but they are only for americans. I found SU^2 but, again, it needs external meshing tool and postproc... So. As far as I understood, it is only a miracle that can help me to find easy software. Maybe someone of you is a wizard's friend? If not, would you please give me some advice about what combination of tools to choose? Which is simpler to learn, OpenFOAM with its standard tools or SU^2 (with which mesher)? Or maybe there is another combination "preproc - solver - postproc" which is simpler than either OpenFOAM or SU^2?

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May 6, 2013, 16:34		#2
JR22 Senior Member Jose Rey Join Date: Oct 2012 Posts: 134 Rep Power: 17	You can try OpenFoam via Helyx-OS (GUI tool). That's a good entry point. Once you grow out of Helyx-OS, you can start diving deeper into OpenFoam. The one caveat is that you have to install it in Linux (preferably Ubuntu 12.04). I installed it inside a Virtual Box and works well. After you get it installed, here is a video that runs you through an external aerodynamics simulation: http://www.youtube.com/watch?v=yJbFnFzDLqo

May 7, 2013, 01:55		#3
Martin Hegedus Senior Member Martin Hegedus Join Date: Feb 2011 Posts: 500 Rep Power: 19	OpenFOAM is not a coupled solver therefore it will not converge for transonic steady state solutions. Someone can correct me if I'm wrong. You'll need to focus on SU2 or Overture, http://www.overtureframework.org/. Edit: I'm not sure if Overture implements turbulence models.