Abstract:
The prediction of scour evolution at bridge foundations is of utmost importance for
engineering design and infrastructures’ safety. The complexity of the scouring inherent flow field
is the result of separation and generation of multiple vortices and further magnified due to the
dynamic interaction between the flow and the movable bed throughout the development of a scour
hole. In experimental environments, the current approaches for scour characterization rely mainly
on measurements of the evolution of movable beds rather than on flow field characterization. This
paper investigates the turbulent flow field around oblong bridge pier models in a well-controlled
laboratory environment, for understanding the mechanisms of flow responsible for current-induced
scour. This study was based on an experimental campaign planned for velocity measurements of
the flow around oblong bridge pier models, of different widths, carried out in a large-scale tilting
flume. Measurements of stream-wise, cross-wise and vertical velocity distributions, as well as of
the Reynolds shear stresses, were performed at both the flat and eroded bed stages of scouring
development with a high-resolution acoustic velocimeter. The time-averaged values of velocity
and shear stress are larger in the presence of a developed scour hole than in the corresponding flat
bed configuration.
