6DOF Propeller Analysis
 

Hello everyone, I'm currently trying to theory craft how to do a 6DOF analysis of a propeller attached to a body.

Does anybody has any kind of experience on this, for example using Sliding Mesh inside a overset or using some sort of nested oversets?

any source of resources which I can read/access to would be highly appreciated. I did already check users guide - theory guide and some forums

thanks

If your propeller is fixed in one place and rotating, you probably won't need overset or 6DOF. You just need a separate cell zone that's rotating.

6DOF is usually for fine mesh that sticks to a body that translating in coarse mesh space, liker free fall.
Anyways, you know your project the best. There is some example on using multiple overset mesh online, just create a bunch on gradually refined mesh and append them all. https://www.youtube.com/watch?v=jukm6w3vMXc

If you can explain the physics of your problem and how overset or 6DOF fits then I can help you more here.:)

Thanks Indra!
The reason I want 6DOF is to observe the movement of my object that is tied to an impeller. For this purpose, I'm currently trying a sliding mesh inside an overset mesh, which is again inside a much coarser mesh as you suggested.
The properties of propeller is 1 DOF Rotation with respect to the body, and 6 DOF Rotation with respect to the global domain.

Also, I did a pretty heavy research on YouTube as well regarding this topic, and unfortunately couldn't found no similar case :(

So i'm guessing you'll need a non-conformal mesh inside the overset mesh for your propeller roatation using sliding mesh. Other than that everything else is more or less the same. I believe if you use mesh motion, you wouldn't need 1DOF for propeller. You obkect on the other hand could be a 6DOF wrt global domain. I personally haven't done this kinda mix of sliding mesh in overset I guess it'll take you a couple of tries to get this right. If you apply 1DOF to propeller wrt body, it could work but I'm not sure what kind of problems you'll face. You'll need to try it first. Try a simple geometry with fan with 6DOF and overset and try to get you methodolody right. Go about it one at a time. Try 6DOF first and then implement overset.

So, I currently solved some of my problems without using UDF's. Here is my updates for anyone interested.

- Currently my propeller has 1 DOF wrt the body's geometry, and the body has 6DOF itself. This is defined by the GUI of Fluent, 22R1.
- While testing with some force on the body and radial velocity on the propeller, I can see both movements are what I wanted. This is done by Preview Mesh Motion.
- Body of my object has an Overset Mesh, with a Sliding mesh domain inside for the propeller.
- When I run the simulation, I see no movement for the body. I'm guessing this is because the forces on the propeller is not transmitted to the body itself. Trying on some fixes for this like a scheme execute command or another UDF.

Hi Anan,

I am working on a problem similar to yours. I have a rotating fan attached to a static body. The fan is enclosed in 1D rotating overset zone.

To make 3D overset mesh, I introduced a small gap b/w fan and the body. The overset boundary seems reasonable - with no orphan cells.

My problem is exactly like yours, the fan is not giving any roll angle. Neither does it record any rolling moment.

Did you happen to solve your problem? What worked?

Hi aykay,
The problem I was facing has a dynamic body with 6DOF characteristics which has a propeller attached to it. I managed to solve it by attaching a MRF zone which contains the propeller, inside the overset domain, which has 6DOF movement. After this, giving the MRF zone 0 angular and axial movement by setting it's dynamic mesh properties all to zero, with respect to the overset domain.

Thank you for the response. One more question please:

In one of your comments, you mentioned "When I run the simulation, I see no movement for the body. I'm guessing this is because the forces on the propeller is not transmitted to the body itself. Trying on some fixes for this like a scheme execute command or another UDF."

Did you find a fix and eventually saw movement of the body with 6DOF?

Hi Anan I would like to connect with you on this I am also facing same issue.
What do you mean by MRF zone inside overset domain.
Are you creating two cell zones for propeller ?