I just noticed when driving that wind turbines rotors have a slight bend at the very end of every rotor. Is this a damaged wind turbine or is it intentional?
I just noticed when driving that wind turbines rotors have a slight bend at the very end of every rotor. Is this a damaged wind turbine or is it intentional?
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Turbine blades get quite long. Because it’s long, the wind easily bends the blade inwards which makes the turbine less straight and less efficient. If, however, you pre-bend the blade in the other direction (e.g outwards), the wind will bend the blade straighter during actual operation.
It’s intentional to maintain the local blade section’s angle of attack. The closer along the blade you get to the hub, the slower the blade is moving relative to the ambient air (V = rotational rate * radial distance from center of the hub) compared to the wind velocity. This means the local angle of attack changes, so therefore they twist the blade to compensate.
Wind turbines work best when the blade goes through the air side-on. In the middle “side on” means the side of the blade faces into the wind. At the outside of the blade the blade itself is moving, so adding the wind speed and the blade speed means that the air is hitting the blade from an angle, so the edge of the blade has to twist to match that angle
Think of a windwill as a bunch of wings stuck together. Wings are curved along the top, but because the windmill is a huge circle, if it’s big enough across and in strong enough winds it will spin so fast and with the edges so far from the center that the wind will hit the edge as one shape and the length of the blade as another. So they bend them so the whole thing is the right shape as the wind touches it. Think of each blade in a bent windmill as two wings stuck together to account for this.
Windmills in areas with less strong winds generally have blades without the bend.