Please help me with a car project.

Hello to all,

I just installed CAE Linux and have done my first pipe tutorials successfully.. Very nice package of software this CAE Linux is.

Anyway I would like to design a car for a car design contest for the year 2014. The car should be a mesh model
made with Blender and only with open source free software. I have few following questions related to my project:

1. How does Blender co-operate with Salome and OpenFOAM? If I export - say the car - as a .stl mesh can I use
Catmull - Clark subdivide tool to make the mesh more smooth? The file should be first made with a Blender and then
imported to Salome for .med transfare and I would like to know will it work at all? What are the chances that the file transfare will fail?

2. Can I use Saturne for this kind of wind tunnel test? I would like to use Saturne once it has a GUI which is nicer
than OpenFOAM GUI .

3. What kind of preprocessing I should I do for this kind of .stl file in Salome before it works in OpenFOAM or Saturne?

4. Does anybody know a good tutorial for Saturne or OpenFOAM for this kind of wind tunnel test? As you can see from my questions I am
novice and I do not have an engineering background but I am industrial designer by my education. However I see this
CFD as an interesting challenge and I would like to learn a lot about it.

As a consequence I would like to create a design which looks good but is also aero-dynamical. Please help me and thanks in advance.

Hello all,

Here is my first attempt to make a simulation of the sportscar in a windtunnel.

Salome and .med file I can send via email of the windtunnel and the sportscar if you are really interested.

The car is made in Blender and its should be quite a solid modeling.

But Saturne gives me a following warning below.

Please let me know what I am doing wrong here. I am a novice
to CFD so my mistake may be really simple.




/home/tomm
c
.

---

| Code_Sat
|
EC
MED 3
Reading
----
Date
Processo
Memory
Mesh fi
Mesh name
SIGSEGV signal (access to forbidden memory area) intercepted !
Call stack
1: 0x7f2231b532d9 (libc.so.6)
2: 0x7f223247cb6d (libhdf5.so.7)
3: 0x7f2232642a95 (libhdf5.so.7)
4: 0x7f223247c0e0 (libhdf5.so.7)
5: 0x7f223248bbbc (libhdf5.so.7)
6: 0x7f223248c3ed (libhdf5.so.7)
7: 0x7f223247bd8d (libhdf5.so.7)
8: 0x7f2232487e8b (libhdf5.so.7)
9: 0x7f22324882f7 (libhdf5.so.7)
10: 0x7f22321d8104 (libmedC.so.1)
11: 0x7f223217a6ce (libmedC.so.1)
12: 0x7f223215088d (libmedC.so.1)
13: 0x7f223214694d (libmedC.so.1)
14: 0x4304e6 (cs_preprocess)
15: 0x40ebeb (cs_preprocess)
16: 0x409fd0 (cs_preprocess)
17: 0x7f2231ae9c4d (libc.so.6)
18: 0x404209 (cs_preprocess)
End of stack

Ok...

I noticed that it is best not to use too heavy files...so I simplified the car a lot. That helped, my .stl file was buggy.

Anyway now I have a result like this, and it still says this Saturne that preprosessing is somwhow wrong.

/opt/saturne-2.0.2/cs-2.0/bin/cs_preprocess --mesh TheSportscar3.med --case
SAFDG

.

---

.
| |
| Code_Saturne Preprocessor |
| |
`

---

'

ECS version 2.0.2 (Sat 01 Oct 2011 12:26:01 PM EEST)

CGNS 2.5.5 file format support
MED 3.0.3 (HDF5 1.8.7) file format support
Reading of compressed files ('.gz') with Zlib 1.2.3.3



Case configuration

---

Date : Fri 11 Oct 2013 02:16:38 AM EEST
System : Linux 2.6.32-52-generic
Machine : AMDFireGLPro
Processor : Intel(R) Xeon(R) CPU L5420 @ 2.50GHz
Memory : 8188796
User : tommi2 (Tommi P. Laiho)
Directory : /home/tommi2/tmp_Saturne/46Y7J.SAFDG.10110216

Case name : SAFDG
Mesh file : TheSportscar3.med



Reading mesh from file in MED (EDF/CEA) format

---

Mesh file: TheSportscar3.med


Mesh name: Mesh_3


I wonder what is wrong. Please help and thanks in advance.

Many thanks for your info.

I think the use of a compressible or incompressible flow solver is debatable for wind tunnel testing conditions. If the Mach number is greater than 1 a compressible solver should definitely be used but I seem to recall that it is recommended even when the Mach number is lower. One consideration would be whether this Mach number assessment is performed at a location like the inlet where the peak velocity is known but higher velocities will almost surely be observed elsewhere in the model. Therefore a Mach number prediction at the inlet may underpredict this quantity. I am not very familiar with the use of compressible solvers so it may also be that the physical phenomenon of compressibility is significant at Mach numbers much less than 1.

Since the speed of sound in air is ~340 m/s the mach number at 100 km/h (~28 m/s) is fairly low (Ma = approx. 0.1).

OpenFOAM is a good choice since it will mesh 'automatically' (after proper definition of the mesh dictionary) using nothing more than an STL model of the car. There is even a tutorial for a motorcycle which should be fairly easy to adapt. I was not aware that Code Saturne can use a mesh of a boundary to generate a mesh of the fluid. Forgive me if I am mistaken as I do not follow CFD solver development very closely.

Motorcycle tutorial:
www.vespalabs.org/index.php?title=Projec...M_Motorbike_Tutorial
www.cfd-online.com/Forums/openfoam/72124...orbike-tutorial.html

In CAELinux the files are by default in opt/openfoam***/tutorials/incompressible/simpleFoam/motorBike
They may also be in other folders perhaps for a separate tutorial on a different solver.

I have a couple of tutorials I am very slowly developing for OpenFOAM and Code Saturne:
www.caelinux.org/wiki/index.php/Contrib:BondMatt

Good luck and have fun!
- Matt