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I answer my own question and give a good thanks to DavidPh, who has not really gave the answer, but in fact, it was impossible for him to give it. Here is "why": I'm French, so I've many fire hydrant data but from France. And when applying them to the formulas, the result was wrong... In fact, the problem is not the formula but the way we measure the ...


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The discrepancy is that the pressure as measured by the Pitot tube is not just the kinetic energy term of the pressure, but instead is a combinaiton of static pressure and the kinetic energy term. See if pages 16-34 of the following reference are helpful, though not metric: http://www.southsaltlakecity.com/uploads/documents/%5E_Fire_Flow_Calculations.pdf ...


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If the tips of the propeller blades are moving near the speed of sound a shock wave can form. Supersonic flow has very different character than subsonic. A propeller designed to operate at subsonic speeds will be inefficient at supersonic ones due to shock waves. In general, shock waves cause a loss of efficiency. You might have noticed that subsonic ...


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The highest wind speed ever measured outside of a tornado was 113m/s, approx. one third the speed of sound. Needless to say, no wind turbine will be operational at that wind speed, let alone operate with its wing tips close to supersonic mode. Smells like the pseudoscience it is.


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The statement in the first paragraph "In fact, today’s standard turbines are based on the same physical principles as 18th century windmills." is marketing hooey. They are hanging their hat on the fact that the windmills were unducted props and most of today's turbines are the same, which is true. The airfoils used today are not 18th century designs. They ...



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