Flow around object, fine meshed but fails even slow flow

Hi, I’m tired of wasting core hours. It is time to ask here. I am modeling incompressible flow around a rigid object, a Helicopter. I have created the mesh surrounding the helicopter, and everything is fine there.

The execution fails for many different “slow” inflow conditions. I have been trying slow flows to be sure the execution won’t fail and later jump to higher air flows…

Not sure if the link will drive you to my project, but here I share it [SimScale]

Do you have any ideas on how to solve the issue? Thank you.-

Hello @arvaldez , and thanks for posting your question on the Forum.

The project link isn’t working, but I found one of your projects named ‘Helicopter.’ I noticed that the length of the helicopter exceeds 10,000 meters, which led me to suspect a scaling issue. When encountering such scaling problems, computing the Reynolds number becomes crucial, and turbulence parameters cannot be computed sensibly. I would first recommend checking the model’s scale.

Thanks, Kaan

Hi @kaany, I completely agree with you the CAD import ( at least in my case) always imports kilometric values… Can you point me to where to scale the CAD file? I tried doing that outside, like in Solidworks, but the Simscale import changes to 10e3 factor…

Thank you.-

Hello again @arvaldez !

You will find an option in the CAD Mode called “Scale”, that should be helpful to re-arrange your model.


Best wishes, Kaan

Hello @kaany, it gets better but is still enormous

200m Helicopter can possibly fly near Jupiter, lol

It would be something spectacular to see though! :slight_smile:

You should be able to reduce the scaling factor even more by typing the scale factor next to the sliding bar.

Best, Kaan

The scalling still fails to reduce the size of the object… I can’t go forward. Do you know why?

Interesting! I directly used 0.001 as the scaling factor to begin with, and it works just fine.


Another approach you can try is to setting unit to millimeter when importing your model. This will automatically re-scale model with a factor of 0.001 too.

Thanks for the help. I was able to rescale it. I’m generating the new mesh and will soon run the latest simulation. I’ll keep you updated, if the simulation fails…

Scaling succeded. But the solver still fails to converge… Do you have any suggestions?