Local scour by submerged offset jets

In this paper an effort is made to understand the scour caused by submerged offset jets impinging on a cohesionless sand bed. A square cross-section nozzle and a two-dimensional (2D) nozzle spanning the width of the flume were used to generate the jets. The 2D offset jet experiments were conducted at two values of the densimetric Froude number (F0 = 5·5 and 10) and two receiving water depths corresponding to shallow and deep tailwater conditions. The square offset jet tests were conducted at F0 = 10 and correspond to deep tailwater conditions. Velocity measurements were conducted using a laser Doppler anemometer. For both jet types, at a given densimetric Froude number, progressing from the start of the test towards asymptotic conditions, the geometric parameters used to describe scour were found to be sensitive to the offset distance. Offset refers to the vertical distance between the nozzle invert and the initial sand bed and an asymptotic state refers to the situation where no significant change in the...