Description
When an obstacle is placed in a flow on an erodible bed, a scour hole forms at the footing of the obstacle. On river beds, this phenomenon typically occurs in the vicinity of bridge piers and/or abutments, often leading to the structure collapse.
The movie shows the scour activation at a rectangular abutment (vertical plate). The experiment was performed in the Politecnico di Milano, in a pressurized duct filled with plastic sediments. Erosion of the bed commences at the abutment nose (where the maximum erosion depths are typically measured at the beginning of the process), then the area with high sediment motion enlarges both upstream and laterally. Observation of the sediment motion highlights the effect of the turbulent flow field upstream of the abutment, and the presence of the recirculating wake downstream of it.
Additional notes
More movies can be found on the web site of the Hydraulic Engineering Dept. of the Politecnico di Milano:
http://www.diiar.polimi.it/idra/progetto.asp?id=5.
