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-   -   Simulating a Car with rotating rims (http://www.cfd-online.com/Forums/openfoam-solving/98356-simulating-car-rotating-rims.html)

lovecraft22 March 8, 2012 17:08

Simulating a Car with rotating rims
 
Hi all;
could anyone give me some tips about how to simulate a car with rotating rims (with spokes) please?
I don't want full detailed instructions, just the basics:
- solver
- mesh requirements
- …

Thank you!

akidess March 9, 2012 03:57

I'd compare the rims to a mixer: You'll need a solver than can handle a dynamic mesh wish a sliding interface. If you google for "Openfoam mixer", which gives you e.g. this.

lovecraft22 March 11, 2012 14:43

Thank you Anton;
I don't know if that's my case… From what I read that's actually a rotating mesh, isnt'it?
I'd probably only need a rotating reference frame or the wheels…

What do you think?

akidess March 12, 2012 04:32

If you want to simulate the car with the rims, then you need a dynamic mesh. If you just want the rims alone, then maybe you can get by with a moving frame of reference.

elvis March 12, 2012 05:40

There is a tool that was made for automotive industry (and so on)
have a look at icon´s demo and you get an idea how these simulations can be performed
http://www.iconcfd.com/en/services/f...o-process-demo

in that demo they use MRF for the wheels

lovecraft22 March 12, 2012 10:10

MRF stands for moving reference frame, is that correct? So they are not moving the mesh but they do have a moving reference frame for the wheels only, right?

It also seems that they have a volume which encloses the rims…what's that for?

Thank you!

elvis March 12, 2012 11:10

multiple reference frames (MRF)

is implemented in OF since version 1.4

lovecraft22 March 13, 2012 18:49

So Elvis, you are basically saying that I use a MRF on a portion of my domain such as a whee and not on the rest of it (such as the body of the car), correct?
How do I choose a part to be subjected to a MRF?

Thank you for your help.

Ralph M March 14, 2012 04:58

Lore,
you can also go for the simpleFoam solver and then apply a rotating-BC on the wheels. No need for rotating meshes; just define the wheels as a separate patch and of you go!
Don't know the exact name for the BC, but I'm sure you'll find the name on this forum (another method is to use the BC "bananas" in your U-files. When running the case an error shows up with all the suggested BC's)
Regards,
Ralph

lovecraft22 March 14, 2012 06:15

Thank you ralph.
My problem is that the tyres can be rotating parts and that's easy to achieve… The problem is related to the rims which cannot be just rotating surfaces…

lovecraft22 March 15, 2012 09:42

Hi all;
I enclosed my rims inside a surface called rotatngCells.stl

Now I think I should run cellSet and setsToZone, and eventually these will be entered inside my MRFZones, is that correct?

Should I have the rotatingCells.stl part inside my snappyHexMeshDict and have it meshed?

Thank you!

elvis March 16, 2012 03:42

Dear Lore,

I did not do any car aerodynamic simulation so I do not know the nescessary steps to make a reasonable simulation.

I can tell you that someone in this forum knows it very well, as he worked in the past for Icon maybe Ries Bouwman http://www.cfd-online.com/Forums/members/m9819348.html
is willing to tell you a bit how VW do openfoam car simulations concerning rotating rims.

I listened to some automotive cfd engineers and I think to remember that the design of the rim and even the design of the tire tread has an huge impact on aerodynamics, there is a lot of potential on rim and tread to make good or bad car aerodynamics

lovecraft22 March 16, 2012 04:58

Thank you Elvis. I think I probably found a way on my own to do that. I'll try and run it today and in case it works ?ll post a detailed tutorial.

lovecraft22 March 16, 2012 14:16

I'm still struggling…
I created a cylinder which encloses the rims but what should the boundary conditions be for this surface?

I'm using the k-OMEGA model.

Thank you!

lovecraft22 March 17, 2012 13:54

I managed to get it running.
Now I need to understand what I did and also whether what I did was correct or not…

I set one wheel only to rotate and for sure its wake is quite different from the other wheels…

Maybe tomorrow I'll post a detailed list of what I did and possibly also a tutorial later on…

madact October 23, 2014 01:10

Quote:

Originally Posted by lovecraft22 (Post 349998)
I managed to get it running.
Now I need to understand what I did and also whether what I did was correct or not…

I set one wheel only to rotate and for sure its wake is quite different from the other wheels…

Maybe tomorrow I'll post a detailed list of what I did and possibly also a tutorial later on…

So... I know it's a very old thread, but did you ever get to doing that list or tutorial? Or perhaps there's some other resource for this problem that you could point me to? Ta :)


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