Three-dimensional analysis of propeller local scour near a quay wall

Only a three-dimensional (3D) analysis allows the evaluation of the geometric characteristics of the scour hole and of the deposition mound induced by a rotating ship propeller. These are essential for the estimation of the total eroded area (As) and the total eroded volume of sediments (Ve). The centreline longitudinal bed profiles in confined conditions are investigated for different values of the distance between the wall and the propeller face (Xw), by identifying three different scour shapes for the near wall, the intermediate and the far toe clearance fields, respectively. The maximum scour depth at the toe of the quay wall (ds,nw), which can compromise the stability of the structure, is analysed as function of Xw, by showing that it decreases as Xw increases. Moreover, this trend seems to depend on the propeller submergence depth (h0), unlike to those of the other geometric characteristics of the scour hole and of the deposition mound (i.e., As, Ve and the absolute maximum scour depth, ds), which are only influenced by Xw. It is also demonstrated that the maximum deposit height (hd) is not affected by Xw and h0.