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Let me preface this by saying that I did my research and have r̶e̶a̶d̶ skimmed a lot of papers on new blade profiles for vertical-axis wind turbines (VAWTs).

What I have yet to read about is a blade profile that is optimized with the recognition that in a VAWT (in contrast to airplanes and HAWTs) the blade is constantly rotating around its vertical axis.

To be fair, my intuition might be wrong here, but a blade that rotates a tiny bit along its circular path is still subject to basically the same conditions it was a mere moment before (ie the air molecules have not had time to move far across the profile). Surely this must have an influence (?), but simulation programs (like xfoil) only simulate independent moments in time and do not capture this continuity.

So ... are there blade profiles that are optimized to constantly travel on a circular path?

fho
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  • Also note that I don't want to "solve VAWTs" ... it's just that this seems like an interesting detail that I have not yet seen people talk about. – fho Oct 06 '22 at 13:27

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I am not aware of a publicly available VAWT airfoil library. Yes there are likely optimizations that can be made, but they would be harder to generalize than the lift/drag plots of standard airfoils.

There are two main regimes of vertical access wind turbines:

Darrieous wind turbines have blades that operate at a velocity in excess of the wind speed. These blades use symmetrical airfoils which are well documented in various airfoil databases. When the cord is 1/30th or less of the circumference of travel there would likely not be any optimization advantages. However, as the circumference of travel is reduced (if there are any design advantages for doing this) the rotation may become appreciable and CFD optimization would be beneficial.

Savonius wind turbines use asymmetrical drag and are typically not considered an airfoil. Hybrids do exist however and CFD would be required to optimize.

I modeled a proprietary VAWT design in OpenFOAM for a client back in 2010. OpenFOAM has come a long way since then and would easily be able to handle the analysis if you are looking to investigate further.

ericnutsch
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  • I dabbled in OpenFOAM several times, but never reallt got further than running the examples. – fho Oct 08 '22 at 22:30