Turbulent flow and vortical structures past two low-aspect-ratio wall-mounted finite cylinders at various configurations

Planar particle image velocimetry (PIV) and volumetric particle tracking velocimetry (PTV) were used to investigate the flow over two low-aspect-ratio wall-mounted finite cylinders positioned in close proximity to each other and immersed within a turbulent boundary layer. The effects of the configuration of the two cylinders were studied across a wide range of streamwise spacings, spanwise offsets, and height ratios (defined as the ratio of the upstream cylinder height to the downstream cylinder height). In all cases, the downstream cylinder was positioned at the same location and occupied ~20% of the incoming boundary layer thickness. The flow measurements were made at a Reynolds number of 60,000, based on the boundary layer thickness and freestream velocity. Within the streamwise-wall-normal plane coincident with the center of the downstream cylinder, the planar PIV results highlight the boundary layer perturbation, velocity deficit, and wake turbulence as a function of the cylinders' configuration. The volumetric PTV results highlight the effects of sheltering by the upstream cylinder at the various configurations on the coherent vortical structures past the downstream cylinder.