The Near- and Intermediate-Wakes of Cylinders Under the Influence of Freestream Turbulence

A circular and a square cylinder were subjected to four different freestream turbulence (FST) inflows to investigate their impact on the spatial evolution of the wake. These turbulence intensities spanned from 1.1 to 13.8%, while the Reynolds number based on the cylinder diameter D was \(Re_D \approx 3.3 \times 10^4\) . The wake flow fields were captured using an expansive 2-D planar particle image velocimetry (PIV) set-up, offering a physical field of view extending nearly 1 m in length, or 20D downstream of the cylinder. Elevated FST triggers an earlier onset of apparent self-similar behaviour in both the wake centreline velocity deficit \(U_s\) and the wake half-width \(\ell \) . Moreover, the rise in FST leads to a reduction in the average number of coherent vortices linked to wake vortex shedding, underscoring how the introduction of freestream turbulence disperses the spatial propagation of these vortices.