Effect of armor layer on the local scour formation induced by a deeply submerged circular wall jet in confined channels

A series of laboratory experiments was conducted in a confined channel with a multi-size and density particle bed to study the effect of multiple armoring layer. A wide range of particle sizes was utilized to form armor layers and the local erosion downstream of a circular wall jet was measured. The time evolution of scour dimensions was recorded and the scour profiles of the mixed bed were compared with the scour profiles in uniform sand bed with the same particle size. Three regimes were identified as the initial stage , the quasi-steady state, and the steady state. The characteristics lengths of the scour showed a rapid growth at the early stage of scour development and the growth rate decreased until the scour reached the steady state condition. The maximum scour depth, width, and length were measured in the steady-state condition and the results were correlated with the densimetric Froude number.