Here a framework is given to estimate streamwise turbulence strength (𝜎𝑢, the standard deviation of wind speed) using a combination of microscale and mesoscale data. Via derivation from the mean turbulent kinetic energy budget, a form for mean 𝜎𝑢 in terms of shear exponent (𝛼), stability (Obukhov length), wind speed, and parameters describing the terrain is provided. In particular, microscale map data and a microscale flow model provides complex terrain information such as RIX or flow-inclination angle, to estimate the effect of excess terraininduced turbulence; further, a microscale flow model can be used to get the local 𝛼 per wind direction, while a mesoscale model such as WRF can be used to obtain the wind speed and Obukhov length.
Towards satisfying the IEC 61400-1 standard, this estimate of mean 𝜎𝑢 is extended to give forms for the representative turbulence (90th percentile) as well as its linear variation with wind speed.
|Place of Publication||Risø, Roskilde, Denmark|
|Publisher||DTU Wind Energy|
|Number of pages||18|
|Publication status||Published - 2020|
|Series||DTU Wind Energy E|