Читать книгу Wind Energy Handbook - Michael Barton Graham - Страница 118

Inflow turbulence interacts with the blades and generates noise due to the unsteady blade forces that arise as a result. This noise source is generally found to be a less strong source than the blade's self‐induced noise, although this is not always so. The only obvious method of alleviating the inflow noise is through a control system to mitigate the unsteady loading of individual blades due to the turbulence. Distributed control capable of operation at frequencies high enough to affect the audible noise spectrum is not yet a feature of wind turbines. Inflow noise intensity is mainly only at a level to be of concern in high, gusty winds where, because there is so much wind noise from other sources in the environment, the additional turbine noise is less significant. There is a long history and a great deal of theory developed for the prediction of rotor blade noise due to turbulent inflow because of its importance in noise radiation from aircraft turbojet engines and rotorcraft. The method originated by Amiet (1975) based on prediction of unsteady blade loading taking into account compressibility was originally developed for aero‐engines. It has been further developed and is still current as a prediction method for wind turbine rotors but involves fairly extensive computational effort. Moriarty et al. (2005) have produced a simpler model based on parameterised results for standard blade geometries.