Experimental investigation of scour induced by twin-propeller wash

Abstract

Advancement of technology has improved the efficiency of marine trading activities through use of vessels equipped with twin propellers instead of a single propeller. The progression from a single propeller to twin propellers will certainly increase occurrences of scour unless protection measures are studied and designed accordingly. An experiment to model a ship's twin-propeller wash was conducted on a flat noncohesive soil bed for observation of scour. The asymptotic scour profile was defined in the following four stages: (1) initial, (2) developing, (3) merging, and (4) asymptotic. An equation is proposed to relate the densimetric Froude number, clearance ratio, and reference time scale to the predicted maximum scour depth and area. The predicted equations were found to be highly correlated with the observed parameters. © 2016 American Society of Civil Engineers.