Torodial propeller

hello there, so i am trying to calculate the efficiencies of my toroidal propeller , but for some reason my generated thrust force is negative while the moment is positive, I’ve tried changing the directions etc… but then my moments are negative and the thrust is positive , I’ve even changed the design a little bit but still getting the same results

can someone please tell me where i went wrong , I’m a newbie to cfd and im not sure how to share the link

check the public projects in the name of " torodial propeller by sai amith pc"

and do let me know my mistake

1 Like

Hi @samith, thanks for posting on the forum :slight_smile:

To share a link to your project, just copy the URL on your browser once you open it and paste it here! At any rate, here is the link to your project: SimScale Login

I’m taking a look at your project and will answer you by tomorrow!

In the meantime, make sure to check out these resources:


Hi again @samith,

As I understand it, different from the forces plot, the moments plot will be highly influenced by the point around which it’s being calculated. Choosing diferent points, for instance:



We get very different moments plots for the exact same boundary conditions.

All of that to say that the moments plot is dependent upon the chosen point, so what you need to do is evaluate if the moments for a given axis are not as expected considering the point around which they are being calculated.

That said, why do you think negative moments wouldn’t be expected? Let us know for further discussion!


@igaviano Thanks for your response. I’m designing this propeller for a drone and wanted to know if having negative moments is acceptable. Initially, I was very confused because I thought only positive forces and moments were acceptable. I was also unsure if my boundary conditions were correct or wrong , but now it’s all clarified. After some research, I’ve learned that negative moments can be acceptable if the drone is adjusted accordingly. I really appreciate your input.

Hello Samith, I may be wrong, but as far as I know opposite signs on a propeller, rotor or any kind of blade suggests that “it requires power” to sustain the movement, which is your case. If you were designing a turbine, you would expect the signs to be equal, given that the system “takes power” from the medium, instead of “supplying power”