Dynamic Mesh with Rotating Wheels touching the Ground
 

Hello everybody,

for my bachelorthesis I was given the task to develop a meshing process in order to do simulations with rotating bodies (DynamicMesh) in OpenFOAM.

As a testcase we have taken a car with rotating wheels because my company is very interested in car simulations. In order to simplify the testcase we let a small gap between the wheel and the moving ground.
(that´s not what happens in reality, but the first aim was just to develop the process and show that calculations with OpenFOAM can be done).

Meshes were created separately (similar like it´s described in another thread).

Everything went fine and we can do DynamicMesh simulations now.

But now we´re thinking about to do the next step and want to realize more realistic simulations. The main problem to face with Dynamic Mesh in car simulations is the contact between the wheel and the ground because normally the wheels are cut in aerodynamic simulations in order to consider the wheel deformation.

At the moment it seems quite difficult to me to get an idea how something like that could be realized with rotating meshes.

Another idea to do DyM simulations with the tire touching the ground would be a simulation in which you just rotate the rims and do an mrf calculation or another steady-state approach for the car tire. Has anybody already gained experience with that? Or has anybody advice how that could be realized in OpenFOAM.

I hope I could explain you my problem. Feel free to ask further questions.




Greetings

Chrissi

Hi Chrissi,

I would go for the second approach and use the tire with the rotatingWallVelocity boundary condition. You can use this boundary condition if the tire has all it's faces tangential to the rotation. You would than indeed have the rim in a cellzone that is moved using a dynamic mesh approach, but your tire is in the stationary mesh, but does have velocity (like a spinning disc).

Regards,
Tom

Hi Tom,

that was also my first intention. But it seems a little bit difficult to me how to define the AMI Interface between the Tire and the Rim because there is no mesh between these bodies. And normally i need two meshes (one on each side of the AMI) to define this Interface.

I already read about the ACMI but the appropriate tutorial case doesn´t really catch my problem

Do you have any idea how to deal with this problem? Or is there a special strategy for this?


Greetings

Chrissi

Well I think you can define an interface that has the entire rim encapsulated and ends somewhere on the tire. This is your AMI, it is only an interface between volume cells on the different sides of the interface, there is no connection between vertices on both sides of the interface. I might be able to give you an example, but at the moment this takes a bit too much time.

Hello Tom,

that would be very nice if you gave me a short example. So you would define a cylinder which ends on the tire and surrounds my whole rim? But how can i mesh that? Because my cylinder then is cutting my tire?!

In addition to that I will need two separate parts (rim+tire) or at least two separate regions in my STL file, or am I wrong?

Thanks for your help

Chrissi

Hi,

Finally managed to get an example for you. Most of the time I will not use snappy, so I am not quite sure how everything works for that, but I would suggest looking at one of the AMI tutorials that use snappy (propeller example in pimpleDyMFoam maybe?).

The final case would look something like you can find here (please note that the link will be valid for about 1-2 weeks):
Example case.

This is a case that should have all the ingredients schematically for what you want to do: A wheel, with rims, and an AMI interface that allows the wheels to rotate, but have the tire stagnant that touches the road, but with a rotatingWall boundary condition in order to include the rotation.

Note that it is just an example case (Domain is not split in inlet and outlet, mesh is way too coarse and has no boundary layer mesh etc.) I checked that it ran for a couple of time steps, but it may fail at some moment. For an actual case I would probably have made a fillet or something similar between the road and the tire to mimic a contact patch and loose the sharp edge between them.

So, this case should give you an idea, but you should need to find a way to do this with snappy.

Good luck,
Tom

propller domain meshing
 

hi 2 all
I'm new user of ansys that want to use ansys cfx for a ducted propeller.
i can't mesh my model as good as that my solver give me best results.
how can i mesh my model with boundary layers that have fine meshes near propeller and duct and meshes grow slowly linearly with distance from the duct?
I work with ansys workbench and fluid flow(CFX).
thanks:(

Hello Tom,

could it be that you have forgotten to attach the blockMeshDict respecitvely the createPatchDict? I can´t find them in the file you have uploaded.



Thanks for your help.

Hi Chrissi,

Like I said, I did not use blockMesh/snappyHexMesh to make the mesh, I used a commercial mesher (hence the tetrahedral meshes). It was just meant to give an example. Therefore I do not need to modify it. Please examine the way it was set-up, including the boundary conditions for the wheel/rim/spokes etc.

I think you could recreate this in snappy, just make sure you have the AMI patches as refinement surfaces, STL would probably be best and snap to them from both sides. However I am not really an expert on snappy.

Good luck,
Tom

Hello Dear Tom

And now also need to do the rotating wheels with dynamic mesh . I find your messages here is really very good and helpful .could you also send me the example case, it would be really nice that i could lernen a lot from that.)
Thank you so much

Hi Louvel,

You just caught me during a rather long holiday, so unfortunately I could only respond today. I have created a dropbox so I do not have to use links that expire.

For anyone else reading this thread, the example can be found in my Dropbox.

thank you so much! got it!
and happy new year!
best regard!