Wind tunnel simulation of wind flows with the characteristics of thousand-meter high ABL

The accurate simulation of wind flow in the boundary layer wind tunnel is very important for the relevant research on the environmental and structural wind engineering. Due to the earth's rotation, an Ekman spiral shaped wind direction profile would be generated, which is a common phenomenon in the thousand-meter high atmospheric boundary layer (ABL). However, the simulation of wind direction was overlooked in previous studies. In this study, based on the objectives of wind profiles determined by the field measurement, two twisted wind flows (TWFs) with the characteristics of thousand-meter high ABL are successfully simulated using the modified passive simulation technology, i.e. a combination of a self-developed vane system and the traditional passive simulation facilities. In the two TWFs, the wind speed profiles follow the power-law. The maximum wind twist angles are 24.2 degrees and 14.7 degrees respectively, and the variations of wind directions follow the Ekman spiral. The turbulence intensities fluctuate within the stipulations in Chinese Load Code, indicating that the results obtained in the wind tunnel test are reasonable. The power spectra of wind speed show good agreement with the von Karman spectrum. In order to evaluate the effect of TWF, the simulation of multi targets equivalent straight wind flow (SWF) is achieved. Then, the effect of TWF on the wind loads of megatall building is discussed so as to illustrate the importance of accurate simulation of wind flow. It is found that due to the existence of wind twist angle, for any specified wind direction, the wind force that acts on a thousand-meter high building is no longer a specific value, but varies with the total wind twist angle.