Impact of Swirl on the Round Wake

Abstract The influence of swirl on axisymmetric wakes is a critical area of study, with significant implications for both practical applications, such as wind turbine wakes, and fundamental fluid dynamics research, where even small changes in the mean flow can lead to substantial alterations in turbulence characteristics. Despite its importance, this topic has received limited attention in the literature. This study examines the influence of swirl on the downstream development of a controlled, rotationally symmetric wake. The wake was generated using a rotating porous disk mounted in a wind tunnel, and the flow field was measured using stereoscopic PIV across various swirl strengths. The results suggest that swirl begins to influence the wake at swirl numbers around 0.07, with its effects saturating at swirl numbers exceeding 0.2.