Strong winds in the atmospheric boundary layer. Part 1: hourly-mean wind speeds.
Abstract:ESDU 82026 provides methods for estimating the variation of strong hourly-mean wind speeds in the atmospheric boundary layer. The data are particularly applicable in calculations of wind loads on buildings and structures. The range of applicability includes heights between ground level and the edge of the Earth's boundary layer (500-3000 m) over various types of terrain including those where step changes in surface roughness occur upwind of the site.The methods described, and summarised in calculation sheets, start with a known reference wind speed applicable for a specified terrain and height such as taken from a map of extreme wind speeds. Factors are then given by which this value must be multiplied to account for the terrain roughness at the site in question, for changes in terrain upwind of the site and for different heights above the ground. Separate statistical factors are given to account for return periods and risk of exceedance other than those applicable to the reference wind speed. Guidance on topographical effects is given such as those produced by embankments and escarpments. For the UK a map of the once-in-50-year hourly-mean wind speed is provided, together with factors giving the equivalent directional extremes in 30 degree sectors. Sources are provided of extreme wind speed data in other countries.The full methods for estimating the effect on mean wind speed of terrain roughness changes, height above ground (and topography) are built into the computer program VIEWpac E0108 described in ESDU 01008.
|Data Item ESDU 82026|
The graphs listed below are available only to subscribers.
|Figure 2||The Factor KN|
|Figure 3||Zero-plane displacement height|
|Figure 4||The Factor Ks*|
|Figure 5||The Factor Ks|
|Figure 6 - Part 1||The Factor Kz* = Vz*/u* (equilibrium boundary layer)|
|Figure 6 - Part 2||The Factor Kz* = Vz*/u* (equilibrium boundary layer)|
|Figure 7 - Part 1||The Factor Kz* = Vz/V10 (equilibrium boundary layer)|
|Figure 7 - Part 2||The Factor Kz* = Vz/V10 (equilibrium boundary layer)|
|Figure 8a||The Factor Kx for z ≤ hi. z0 > z01|
|Figure 8b||The Factor Kx for z ≤ hi. z0 < z01|