rotors are moving around and are not fixed in place

[Omar Sanhaji]

Hey I ran two propellors, but they seem be spinning around each other as they rotate the blades. How do i get them to stay in place?

Also is there a way where i can set the desired CT, CP,  solidity, and twist and it make the propellor for me instead of me manually moving the chords around? Because it defaults to a CT of 0.6 and i need it to be 0.005.

[Cibin Joseph]

There's a bug when you use symmetry with propellers. You could duplicate (copy + paste) a single propeller geometry (using the Cut, Copy, Paste buttons in Geom Browser) and change the Y value to -Y as a workaround to create symmetric propellers. Would have to reverse the direction of rotation and adjust the phase angle of one of the props. See attached file. 

Side note: Sometimes VSPAero reports 'the mesh is not closed' after completing the simulation. The window freezes and the viewer cannot be opened. Closing and restarting the OpenVSP window allows the VSPAero viewer to be opened without re-running the solver as the solutions are already written to file.

That second part of your query sounds like a geometry optimization problem. I don't think OpenVSP has that provision-at least not available for frontend users. You'll probably have to set it up using the OpenVSP python API in addition to an external optimization package like IPOPT.

Also, those CT values differ by two orders of magnitude. Are you sure you are using the right convention when computing CT and CP? Note that helicopter and propeller conventions are different.

Cibin

On Wed, Dec 6, 2023 at 12:28 AM Omar Sanhaji <omar.sa...@gmail.com> wrote:

Hey I ran two propellors, but they seem be spinning around each other as they rotate the blades. How do i get them to stay in place?

Also is there a way where i can set the desired CT, CP,  solidity, and twist and it make the propellor for me instead of me manually moving the chords around? Because it defaults to a CT of 0.6 and i need it to be 0.005.

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[Omar Sanhaji]

Thank you so much. It works now. Also I was using the helicopter definition for Cp and Ct which I didn't know was completely different. 

[Omar Sanhaji]

How did you change the rotation direction and change the blade so that it would run correctly?

[Rob McDonald]

Define the propellers as separate props, not as symmetrical versions of a single prop.

No, if you do rotating blades, then you have to design the number of blades, chord distribution, twist distribution, pitch angle, etc.  I suggest you use a stand-alone blade element tool to design the rotors you need.

If you just want to specify CT, CP, then use the actuator disk mode (not unsteady rotating blades).

Rob

[Cibin Joseph]

Yup, besides duplicating the propeller geometry as a separate prop and not using planar symmetry, you need to change the rotation direction.

See screenshot below.

Inside the PropGeom window, in the Design tab , there is a little button that says "Rev" which reverses the direction of prop rotation.

For adjusting the phase angle (or starting angle) of the propeller, you need to change the value of "Rotate" right next to that "Rev" button.

Cibin

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