In this paper, we present the preliminary results of an extended experimental campaign conducted over both unworked (UW) and water-worked (WW) beds using a non-intrusive Particle Image Velocimetry (PIV) system. The main objective of this study was to explore the differences between the two cases in terms of double-averaged (DA) streamwise velocities, DA normal velocities, DA Reynolds shear stress, form-induced stresses, DA Reynolds normal stresses, form-induced normal stresses, total shear stresses, ratio of form-induced stresses to DA Reynolds shear stresses. This study leads to the conclusion that the flow and turbulence characteristics in wall-shear layer of a WW bed are different from those of an UW bed, while they are almost indifferent in the outer layer of flow. Hence, the results from UW bed experiments need to be treated with caution if applied for the analysis of the near-bed flow field.
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