POA * ONLINE SUBSCRIPTION ONLY

ESDU 83045 gives a method for estimating the variation of the expected maximum gust speed with height above the ground for any gust averaging time greater than about 1 second. The method takes into account the roughness of the site terrain and also any roughness changes that occur upwind. The roughness of the terrain affects the hourly-mean wind speed and its turbulence component. Theoretical methods were used to account for these effects and the results combined into a simplified method that is presented in the form of convenient calculation sheets and equations for the data. A gust factor approach is used to relate the maximum gust speed to the corresponding hourly-mean wind speed given by ESDU 82026.The gust factor dependence on averaging time is derived using the spectral density of the fluctuating component of wind speed. The approach assumes an extreme-value distribution that provides an estimate of the maximum value of the fluctuating component and hence the gust speed for any averaging time and time interval within which the wind speed is observed. Gust factors derived using this approach are presented graphically and in simplified equation form. A practical worked example illustrates the use of the data. The full methods for estimating the effects on gust speed of terrain roughness changes, height above ground and averaging time are built into the computer program VIEWpac E0108 described in ESDU 01008.