Experimental study of propeller and ducted propeller’s wake inducted scour

Abstract

This study investigates the scour profile, scour hole depth, deposition mound height, and the positions produced by the propeller and the ducted propeller that vary over time. The terrains produced by the Ka4-70 propeller and the Ka4-70 propeller + No. 19A duct are obtained using a linear laser three-dimensional terrain scanning system. Compared with the Acoustic Doppler velocimetry (ADV) and other approaches, the system presented here could efficiently and precisely capture the terrain. The principle and system layout are elaborated in this work. Notably, the system can perform underwater scanning. Moreover, compared with the ADV, our system is more efficient and has a smaller data interval. The scour profile, max scour depth and height, and their positions over time are analyzed. The development of the ducted propeller scour is faster than that of the propeller. The ducted propeller scour has a longer, narrower, and shallower influence range compared to the propeller scour. The scour hole range is bigger than that of the scour deposition mound. The general trends of the propeller and ducted propeller development are similar. In each development, the terrain is also morphologically similar at different phases. In addition, the relationship between the max deposition mound position and the max scour hole depth is analyzed, and a scour classic formula is used to fit the scour data on a time scale.