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Question regarding the design of a HAWT blade
Thank you, David.
The problem were just solved.
I have 6 graphs displayed.
But the alpha and Cl/Cd graphs are not displayed.
What should I do?
Bob
Hi Bob,
check out the documentation: https://docs.qblade.org/src/user/guigraph/guigraph.html#graph-functionality
Best,
David
Hi David,
After importing an Airfoil from Clipboard, I used Airfoil module analysis, but, It didn’t work.
And I got
– Polar should have at least 10 points (currently: 0)
– At least 5 data points in the range 0 < alpha < 20 needed (currently: 0)
” in the Polar extrapolation section.
Sometimes the message doesn’t shows depending on the Airfoils which I import.
Could you manage that?
I appreciate your kindness.
Bob,
Hello,
are you saying that the XFoil analysis is not working properly for an airfoil? Could you explain the issue more precisely and maybe share a screenshot of the issue?
At least 5 data points in the range 0 < alpha < 20 needed (currently: 0)
” in the Polar extrapolation section.
The above error message is shown when you try to extrapolate a polar that does not have enough data or is empty – so this is normal if XFoil fails.
BR,
David
Hello,
I have designed a forward wing, but the efficiency exceeds the Betz limit.
Why is this?
If you don’t mind, please advise.
Thank you for all your replies.
Bob
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Hi,
your simulation is not converged yet. Opposed to a imple steady BEM both the unsteady BEM and the Lifting Line take into account the unsteady wake dynamics (or wake development). This means that it takes a couple of rotor rotations until the CP value has reached a steady state value. In your case you need to either simulate for a longer time or set the “Convergence Acceleration Time” to some time larger than zero so that the rotor reaches its steady state faster.
Best,
David
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I appreciate your reply.
I have tried setting the “Convergence Acceleration Time” to 10, 100, and 1000, and the efficiency is 0.56, which is still greater than Betz’s limit.
Bob,
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Hey Bob,
the Betz limit is around ~59%, so it should be ok…
Best,
David
Hello David,
I have two questions.
The first is that the analysis result of Cp of “rz_0.3_6” in the attached file “final” is 1.17, which exceeds the Betz limit. Why is this? I think the values are converging.
Second, what is the difference between the Cp in the BEM and the Cp in the simulation with the icon of the rotating windmill and vortex? Sorry I have not read the manual properly.
Bob
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