Investigation of the relation between bridge pier scour depth and vertical velocity component

Local scour around bridge piers and its consequences can be considered as an important engineering problem. this study was conducted in a 18 m long and 70 cm wide rectangular flume with sediment median diameter of 0.43 mm by using two bridge piers having diameters of 6 cm and 9 cm. the duration of 5 experiments were limited to 4 hours. during the experiments, the evolution of scour depth (𝑑𝑠) and the three-dimensional velocity at 4 cm above the bottom and 6 cm upstream part of the bridge pier was recorded as a function of time. the relationship between the vertical velocity component (𝑉𝑧) and scouring depth was investigated and an equation for the dimensionless forms of these parameters was proposed. it is observed that the proposed relation is in accord with the limited data found in literature.