The effects of freestream turbulence on the near- and mid-field wake of circular and square cylinders

Cylindrical objects often appear in both natural and artificial environments, and are often subjected to turbulent incoming flows. Furthermore, they are often found in groups, where the flow field around any particular element will interact with other elements. Thus, it is crucial to understand how the wake behind these cylinders is influenced by different incoming turbulent flows, particularly in the near- to mid-field regions, where interactions with other elements can be expected and do not necessarily follow universal laws. Using planar PIV, we investigated the wake of a circular and a square cylinder up to 20 cylinder diameters downstream, or 1 m in physical length. Four different inflow conditions are generated with an active grid, with the freestream turbulence intensity levels ranging from 2% to 13%. The Reynolds number is approximately 50 000. Preliminary analysis shows that the coherent structures in the wake are suppressed with increasing freestream turbulence level, and that mean velocity recovery in the wake is promoted. The centreline velocity deficit and the wake half-width follow their expected power-laws in the streamwise direction. Subsequent analysis will focus on how the self-similar behaviour of the wake are influenced by the freestream turbulence.