The effects of sheltering on the flow over two finite wall-mounted circular cylinders immersed in a turbulent boundary layer were experimentally investigated using Union College's water channel. Both the spanwise offset and streamwise spacing between two cylinders were adjusted to investigate how the extent of sheltering the downstream cylinder affects the flow structure in its wake. Both cylinders had a height of 12 mm and a diameter of 4.8 mm resulting in an aspect ratio of 2.5 and were placed in a turbulent boundary layer with a thickness of 60 mm. Five cases of cylinder configuration were investigated including four cases with a streamwise spacing of 6 cylinder diameters (d) and spanwise offsets of 0.25d, 0.5d, 1d, and 2d, and one case with a streamwise spacing of 2d and a spanwise offset of 1d. The flow was measured using a 3D particle image velocimetry (PIV) system. The time-averaged velocity and vorticity were analyzed to highlight effects of streamwise and spanwise variations between the two cylinders. An arch-vortex was present at the trailing edge of both cylinders for all cases investigated. It was found that one pair of counter-rotating vortices exist for all cases at or below a spanwise offset of 1d, whereas two distinct pairs exist for the case with a spanwise offset of 2d. It was also observed for the 0.5d and 1d spanwise offset cases with a streamwise spacing of 6d that the upwash was asymmetric about the centerline of the downstream cylinder. The data suggests this asymmetry may be due to the change in streamwise velocity across the width of the cylinder increasing upwash on one side. It was evident the cases with a lower spanwise offset resulted in greater sheltering capabilities by reducing the velocity deficit region.
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