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72

The vane has to be designed so that it has a preference to point in the right direction. In the example that you included, this is implemented by the flag at the back providing a broader cross section than the arrow head and also by the rooster standing slightly to the back half of the arrow. You are correct that if the vane became perfectly anti-aligned to ...


13

When the wind blows perfectly parallel to the wind vane's long axis, there is no rotational force on the wind vane. When the wind direction is not parallel to the long axis of the wind vane it will exert a turning force on the vane until the wind vane is parallel to the wind direction. The force of the wind on any part of the wind vane depends on its (...


7

When we model aerodynamic forces like this, one of the very useful tools is a "center of pressure." The center of pressure is a point where you can pretend all of the aerodynamic forces are exerted on that point and get the correct behavior. It can move as the angle of attack (AoA) changes, meaning the angle between the vane and the wind, but at any ...


7

While it's possible to analyze this in terms of least energy, it's not very straightforward. That's because it's not the weather vane's energy that is being minimized, but the wind's. The wind does work on the weather vane, which then causes friction, converting the energy to heat. Suppose the weather vane starts out perpendicular to the wind and rotating. ...


3

In everyday life the word drag tends to mean quadratic drag, and this is a complex process involving turbulent flow. The quadratic drag equation isn't a fundamental one but instead is an approximation. This makes it a poor example for your question. It's easier to see this if you consider just the force when you make a fluid flow as this is nice and simple. ...


2

Wind vane will always point to the direction from which the wind is blowing. I.E., if wind is blowing from East to West, then the arrow of the wind vane points to 'East'. The pointed end of the arrow offers least resistance to wind. Therefore, the arrow achieves the state of equilibrium by pointing itself against the wind (Direction from which the wind ...


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