当吉达塔的框架（设计达到1公里）时，需要对风气候的建议，在地球大气边界层上方约500 m处，他们转向RWDI咨询工程师和科学家。
RWDI的挑战是，风工程分析的标准方法无效。Typically, an engineer develops a model of wind characteristics at the site, based on design wind speeds provided in building codes or generated from historical wind measurements, and then extrapolates up to the building’s height using simplified engineering models of the boundary layer, where wind speeds depend on the roughness of the topography, says Jon Galsworthy, an RWDI principal. But, above the boundary layer, weather is determined by the effects of larger masses of air.
|
|
rwdididn’t think standard practice would be good enough. Instead, it began by using historical data from the Jeddah Airport Metrological Station, including 17 years of wind data from balloons, and extrapolated the data using advanced simulation techniques. But that approach has its limits, says Galsworthy: Balloon data does not accurately represent wind climate in the upper reaches because balloons are launched only twice daily and rarely in storms. To get the hourly resolution needed to model the wind near the tower’s top, RWDI performed mesoscale modeling, using the state-of-the-art Weather Research and Forecast Model, which draws on the expertise and data of many governmental and academic institutions.
“Other wind engineers would have scaled up [from boundary-layer wind data] without even thinking about it,” says Robert Sinn, a principal of the tower’s structural designer, Thornton Tomasetti.
