Author(s): Giuseppe Curulli; Andrea Antonella Graziano; Nadia Penna; Roberto Gaudio

Linked Author(s): Giuseppe Curulli, Andrea Antonella Graziano, Nadia Penna, Roberto Gaudio

Keywords: Propeller scour; Quay wall; Confined condition; Photogrammetry technique

Abstract: The increasing in global maritime trade requires the use of large ship propellers that can create damages inside harbour basins, such as structural failure of quay structures due to the erosion of the bed induced by the propeller jet. Hamill et al. (1999) examined the scour hole due to propeller jet with and without a quay structure (confined and unconfined conditions), providing equations to evaluate the maximum scour depth. The scour hole is not symmetric with respect to the propeller longitudinal axis, as recently demonstrated by Wei et al. (2017) and Penna et al. (2019) in confined and unconfined conditions, respectively. Furthermore, analysing the confined condition with two propeller diameters, three rotational speeds and three wall distances from the propeller face (X_{w}), Yüksel et al. (2019) found that the presence of a perpendicular quay wall produces a deeper scour depth then in unconfined condition. However, there are limited works regarding the three-dimensional (3D) analysis of the scour hole induced by the propeller wash in confined condition. Only the 3D analysis of the bed surface allows a detailed description of the main geometric characteristics (e.g., maximum scour depth, length, width and eroded and deposited sediment volumes). In this study, the maximum scour depth at the toe of the quay wall, as well as the other geometric characteristics, were investigated under a constant propeller rotational speed (480 RPM), eleven distances from the propeller and two elevations of the propeller from the bed surface (h_{0}). The scour profiles along the longitudinal propeller axis and at the wall were measured at predetermined time intervals using an Acoustic Doppler Velocimeter (ADV). The photogrammetry technique, combined with the use of a 3D Terrestrial Laser Scanner (TLS), was applied to acquire the equilibrium bed surface and create a high-resolution Digital Elevation Model (DEM). The comparison between confined and unconfined longitudinal profiles at equilibrium shows that the scour hole is highly influenced by X_{w}, which causes three different shapes of the equilibrium scour profiles depending on its value: the near, intermediate and far toe clearance fields. Finally, new equations among the involved variables are proposed, by focusing on the eroded area (A_{s}) and eroded sediment volumes (V_{e}) versus X_{w}. References Hamill, G.A., Johnston, H.T., Stewart, D.P. (1999). Propeller wash scour near quay walls. Journal of waterway, port, coastal, and ocean engineering, 125(4), 170-175. Penna, N., D'Alessandro, F., Gaudio, R., Tomasicchio, G.R. (2019). Three-dimensional analysis of local scouring induced by a rotating ship propeller. Ocean Engineering, 188, 106294. Wei, M., Chiew, Y.M. (2017). Influence of toe clearance on propeller scour around an open-type quay. Journal of Hydraulic Engineering, 143(7), 04017012. Yüksel, Y., Tan, R.I., Celikoglu, Y. (2019). Determining propeller scour near a quay wall. Ocean Engineering, 188, 106331.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022151

Year: 2022