Author(s): C. Adduce; G. Sciortino; P. Mele
Linked Author(s): Claudia Adduce
Keywords: Velocity measurements; Turbulence measurements; Wall jet; Local scour
Abstract: Velocity and turbulence measurements downstream of a sill followed by a rigid apron were performed. Three runs were conducted at different scouring stages: flat bed, 50% of the maximum scour depth and 100% of the maximum scour depth. For all the scouring stages, the vertical distribution of the horizontal velocity component, measured over the rigid apron, was found to be similar to a wall jet. When the bed is flat, the wall jet velocity distribution changes into a free surface velocity distribution, as the distance from the apron increases. When a scour hole develops downstream of the apron, the wall jet velocity distribution changes into an “asymmetric free jet” velocity distribution, till the abscissa of the maximum scour depth. Turbulence intensities, along both the vertical and the horizontal axis, were found to decrease as the distance from the sill increased, for all the scouring stages. A similar behavior was observed for dimensionless Reynolds stresses over a flat bed. When a scour hole develops downstream of the apron, dimensionless Reynolds stresses show positive values close to the bottom both inside the scour hole and downstream of the dune.