Abstract:

ESDU 85020 is one of a series giving comprehensive turbulence characteristics for neutral atmosphere conditions which includes strong winds. It provides turbulence intensity, Reynolds stresses, probability and spectral density, and integral length scale for longitudinal, lateral and vertical components of wind speed at a single point. The data apply up to heights of at least 1000 ft (300 m) and to a range of terrain equivalent roughnesses, including upwind terrain with roughness changes. The theoretical background to the derivation is given, and uses similarity theory applied to the atmospheric boundary layer and models based on measurements from the most reliable sources. It allows extrapolation of results obtained at moderate wind speeds to much higher wind speeds when, in particular, longer length scales are found. Modified spectral equations are derived that account for anisotropic turbulence near the ground.