Evolution of downburst-like flows produced by an active-controlled multi-blade facility

The intricate dynamics of vortex structures within the downburst outflow region present significant challenges in studying flow evolutionary features, which are crucial for understanding the effect of such flow on various structures. This study aims to reveal the evolutionary features of downburst-like winds produced by an active-controlled multi-blade (AMBS) facility, using the particle image velocimetry tests and the large-eddy simulation (LES) studies. The numerical simulation indicates that the wind velocity profiles, nonstationary wind velocity time history, and the transient flow patterns of the downward flow impinging on the ground can be well simulated by the LES method. For stationary winds, a series of columnar vortices are produced, and the vortices tend to be more organized as the maximum velocity appears at a lower height. The proper orthogonal decomposition analysis manifests that the primary vortex region is affected by multiple modes of the fluctuating wind field. In addition, the primary vortex structures of the AMBS-generated flow present apparent evolutionary features. During the downward flow impinging on the ground, the nose-shaped wind velocity profile gradually forms at the turntable center and is well developed when the maximum velocity is reached. This observation is in accordance with the findings in available full-scale measurement campaigns.