Questions on Windfarm Assessment Tool

Which Wöhler coefficient to use in WAT?

When investigating the safety of a particular component you must select the Wöhler number for the material it is build of. When verifying the safety of the entire turbine you should select the highest Wöhler number of all components – usually that of the blades. A Wöhler number of m = 10 is a slightly conservative value for glass fiber, but please check with the manufacturer.

Measured turbulence intensities in WAT?

At the moment WAT has no support for measured turbulence. The reason is that calculation of effective turbulence needs the 90% confidence levels of the TI at all wind speeds, all wind directions, all turbine sites, and all seasons. Such detailed measurements are difficult to obtain, and we have not found a procedure for reliable extrapolation of measurements from site to site. WAT imports TI estimates from the file produced by the WASP Engineering script 'WAT 2(Excel)’. One way to include local measurement could be to edit this file, but please remember that WAT assumes the input TI to correspond to neutral conditions.

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