Characterizing wind tunnel fans for large-scale turbulence generation

Wind tunnel testing requires the accurate replication of natural flow characteristics. In wind engineering and wind energy research the generation of realistic wind conditions is needed to capture the system dynamics. In particular, large vorticose structures can induce correlated forces on bridges and high-rise buildings, potentially leading to dangerous instabilities. Traditional passive turbulence generation methods, such as grids and spire elements, are limited in turbulence scales and intensity. Active techniques like moving grids, while more effective, struggle to generate low-frequency components and often come with high installation costs. A promising, cost-effective alternative is the active control of the facility's fans, which can inject energy into the low-frequency range of the turbulence spectrum, allowing the study of transient phenomena, reproducing non-synoptic winds and other flows with custom characteristics. This study presents a straightforward methodology for characterizing wind tunnel fans as turbulence generators, offering insights into their potential and limitations.