Influence of propeller clearance on the jet scour process in restricted water

Abstract

Rapid development of inland waterways and marine transportation has resulted in the construction of large ships and an increase in ship speed. Consequently, severe local scour erosion of restricted water beds occurs due to propellers, endangering the surrounding buildings and navigating in the scour area. Thus, investigating bed scouring caused by propeller jets for water-related structures and maintaining navigational safety in restricted waterways is highly important. Therefore, this work combines propeller jet wash flume experiments and dimensionless analysis to investigate the evolution of the three-dimensional (3D) morphology of bed scour with varying clearance heights and the use of noncohesive sediments. The temporal evolution of jet scouring was manifested mainly as the development of the scour area's length, depth, and width, and the entire scouring process could be divided into initial, development, and equilibrium stages. The initial stage occupied more than 60% of the scouring process, and the shape of the center profile of the scour area can be expressed by a third-order function. By analyzing the scour depth variation with time, this study proposed a logarithmic equation for the temporal development process of the maximum scour depth in the scour region, which was used to predict the variation in the maximum propeller depth on the surface of the noncohesive sand bed with time.