Generation of downburst outflow in a traditional wind tunnel using multi-blade flow control device

The thunderstorm downbursts impose a great threat to civil engineering structures and the experimentation for such nonsynoptic winds plays a significant role in the characterization and quantification of relevant aerodynamic loading. This study focused on the generation of downburst outflows in the conventional boundary-layer wind tunnel with a multi-blade flow control device. The installed device in the test chamber of the wind tunnel redirected the flow with the rotation of the blades to generate the wind velocity profile of downburst-like outflows. The blades were controlled to be rotated in an independent manner (e.g., various rotation angles of blades) to generate the acceleration effects and facilitate the misture of the flows, resulting in desirable wind velocity vertical profiles. Additionally, the downburst flows with different length scale could be reproduced by different combinations of the blade rotation, which could be applied to the wind tunnel experiments of the downburst wind-induced effects on the structures with various scales. A series of wind tunnel experiments and numerical simulations were conducted to validate the replicating of downburst outflows, and the results exhibited a similar profile to that of full-scale downburst events.