Power of three: Can anyone explain the design of modern wind-powered machinery? The ubiquitous three-bladed turbine that wind farms use suggests that this is the optimum shape but doesn鈥檛 the air that flows between the blades without restraint represent lost energy? Why three blades, and not two or twenty? Low-pressure turbine blades in aero engines or hydroelectric stations have a large number of blades spanning the entire circumference, and so do traditional windmills. Surely the many years of widespread use suggests this must be a very efficient design, so why is it not used in wind farms?
Airless: I regularly ride my light motorbike in a tunnel section of motorway and have often wondered why air resistance in the tunnel is much less than in the open country, all other conditions such as road incline temperature and wind being equal.
In the smoke Major Asian cities such as Manila and Bangkok have a terrible reputation for traffic congestion and environmental pollution. I have noticed that many commuters in these areas cover their noses and mouths with handkerchiefs and the traffic police are issued with dust masks. Does this actually provide any significant health benefits, or is it simply cosmetic and psychological?
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