Scouring by Cycloidal Ship Propellers

With high maneuverability and precision in thrust control, cycloidal propellers are an advantageous choice for operations of vessels in proximity to structures like harbor facilities. However, the yet unexamined phenomenon of scouring induced by these propellers can pose potential threats to the stability of quay walls. This article presents an original investigation of scouring by cycloidal propellers, based on laboratory experiments conducted in a 2-m-wide flume operated in still-water mode using a model Voith Schneider propeller. The results show that cycloidal propellers primarily drive scouring via a ground vortex created by propeller suction. The vortex was observed to intermittently entrain suspended sand, while the upward-directed propeller jet remained largely in minimal contact with the sediment bed. These findings highlight distinct scour dynamics compared to screw propellers and underscore the need for further investigations to improve scour prediction and inform design practices for marine infrastructure.