Unexpected Upward Velocity Vectors in Drone Hover Simulation

[ceckert]

Hi,
https://www.simscale.com/workbench/?pid=3923271815672441018

I’m trying to simulate the velocity fields of multi-copter drones in a hover state, out of ground effect. I’ve followed all the relevant tutorials I could find on the topic. I double-checked the rotation directions of the propellers, using negative values for counterclockwise rotation and positive values for clockwise.

Unfortunately, the results show the velocity vectors going upwards instead of downwards, which is not what I expected. As a SimScale newbie, I’m not sure where I went wrong. I’ve already double-checked all the small tweaks I’m aware of that could potentially cause this upside-down behaviour.

I’d really appreciate any help or advice from community members with more experience in airflow simulations for drones.

Thanks in advance!
Christian

[shenoy]

Hey @ceckert ,

Some observations comparing to a similar tutorial we have,
The atmosphere boundary condition would be set up differently with zero gradient to visualize results purely from blade rotation. The following settings that are currently being used would not mean a zero-gradient flow through the domain.

Since you are not using Symmetry boundary condition, you would have to assign all outer faces to this custom boundary condition as follows:

For the direction of blades, I suggest you try to reverse the direction of the blades and check if that gives you the results you want. Everything from a solver and boundary condition perspective looks good other than the previous point I made. Let us know how it works out.

Best,
Satvik