Here we can place different blade designs, airflow simulators and wind theory. We could try to get clear what does and what does not work well.
The goal of this section is to capture as much energy from the wind, by reducing speed (making the blade speed up) or deflecting the airflow (moving the blades in relation to the vector of incoming wind and outgoing wind), in the best possible manner, by comparing different size and shapes of blades. Questions that comes in mind are: what is the best width/height ratio, what is the best size in general, how many segments should it have (2 at 90 degree angles is common), or should it be spiral shaped.
A darrius is like a spiral savonius, with nothing near the axis, and a very wide, small blade. They vibrate like hell, and break down easy. They also are visually unacceptable in dense populated areas.
There is not much good free airflow software. One I did find was a slow, mostly not working, 2d airflow simulator. 2d Airflow illustrator, but it is a pain, since I often wait for 15 minutes in vain, but it is capable of uploading a bitmap (width and height have to be faculties of 2, like 4,8,16,32,64,128,256,512 or 1024), where white is air, and black is solid. You can fiddle with some settings, and then request a movie, and hope for a result. But still, a very nice piece of software. Thumbs up, for prof chernyshenko!
So, here, we should try to create a wind capture device, that translates that energy into a rotating, vertical ax, with as much torque times rpm as possible, with as little blade-space as possible. The rotating ax is what we deliver to the boys of engineering at building structure.
