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Thrust force with rotor is still
I am using Qblade to simulate a practice VAWT project. I like to learn the thrust force when the rotor is forced to be still in high wind speed. So I set the windspeed at 15 m/s, and I set the rotor speed to zero. The setting is accepted, no issue.
But during the simulation, the software is going to nowhere. It seem to me the software is always at step 1 when the whole procedure finishes. So, the result is invalid.
Is there any good way to simulate the thrust force with still rotor?
Thank you.
Ron Ye
Hi Ron Ye,
I’m not entirely sure I understand your explanation. However, when setting the RPM to zero, you should be able to determine the thrust force for the “locked” rotor.
If you’re simulating using the LLFVW method, I recommend disabling the “shed” and “trailing” vorticity. The induction effect is negligible in this case, and the shedding of wake elements can introduce issues for a locked VAWT, particularly where some blades may experience a constant angle of attack exceeding 180°.
BR,
David
Hi David,
I guess I didn’t ask the question correctly. See the attachment screen shot.
In this picture, I am watching the Ct (Thrust Coefficient). The rotor speed is zero. I see Ct keeps zero. So, I assume the thrust force is zero. But I know the thrust force can not be zero. If the rotor speed is not zero, so the Ct will be some number. I can use Ct to calculate the force. In this case, Ct is zero. How do I calculate the thrust force? Is there anywhere the thrust force is available for me?
Thank you.
Ron
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Hi Ron,
thanks for the clarification.
The reason the Cp and Ct values are zero is that the values you are referring to are the averaged values over one full rotor rotation.
For VAWTs, Cp and Ct vary with the azimuthal rotor position. In the simulation model view, these values are displayed as rotation-averaged quantities. Since your rotor is not rotating in the simulation, the average remains at zero.
To see the instantaneous values, check the ”Aerodynamic Time Graph”, where you’ll find:
- Momentary Power Coefficient [-]
- Momentary Thrust Coefficient [-]
These show the real-time Cp and Ct for the current rotor position, which is likely what you’re looking for.
Best regards,
David
