Propeller jet flow scour around a pile structure

Abstract

In this study, the scour induced by a propeller jet around a single pile was examined experimentally on four different non-cohesive sediment beds. The initiation of scour formation was found to be related to the densimetric Froude number (Frd), propeller diameter (Dp), and the gap of the propeller (G), which is defined as the vertical distance between the centerline of the propeller and the undisturbed sand bed. Three types of scour profiles were defined that can be classified according to a) the scour depth at the upstream toe of the pile (So), and b) the scour at the downstream section of the pile (Sd). Scour profiles were also found to be highly dependent on the densimetric Froude number (Frd) and pile diameter (do). Scour profiles and scour depths at the toe of the pile (So) were investigated at different distances between pile locations and propeller face (X), pile diameter, sediment bed material size, propeller diameter, speed, and gap. New empirical equations were proposed for the estimation of scour depth at the toe of the pile. The locations of the pile (X) were also investigated to assess whether the predominant scouring mechanism was the propeller jet or the pile mechanism.