Migrating scour depth around a spur dike with downward seepage using multiscale characterizations

Abstract

The current work uses an experimental method to analyse a multiscale statistical assessment of scour depth surrounding the spur dikes with downward seepage. The experiments used three T-shape spur dikes arranged in three series and provided outward from the channel's bank. A no-seepage condition and two distinct seepage velocities, VS1 = 0.09 mm/s and VS2 = 0.18 mm/s, were used in the experiments. Seepage from a channel affects the morphological behaviour and stability of the channel's bed, leading to changes in its hydrodynamic characteristics. In addition, downward seepage movement shifts the flow near the channel boundary and weakens the particles' stability. Thus, the streamwise velocity and Reynolds shear stress increase near the bed. As the seepage velocity increases, the local scour formation also rises relative to the channel's bed until the channel reaches a state of equilibrium. The celerity of scour depth for both time and length scales depends on the amount of downward seepage. Initially, higher seepage leads to faster changes in the scour depth, but over time, this rate decreases until it becomes constant. The bedform elevations' tails are thicker initially, but they become thinner and closer to the Gaussian distribution curve over time.