The project will determine the impact that maneuvering propeller-driven vessels have on the transport of sediments and munitions resting on, or just underneath, a local sediment bed. Naval ports may contain remnant underwater unexploded ordnance (UXO) from past military activities. The constant maneuvering of ships at the surface, as they enter and exit the port, likely causes significant particle suspension and consequently the potential undesired motion and transport of UXO. For this project the research team will investigate the potential for UXO motion by addressing (1) the characteristics/magnitude of turbulence and large-scale coherent motions emanating from prop wash and impinging on the sea bed; (2) which flow structures from maneuvering ships are primarily responsible for altering sediment suspension; and (3) the effect of these flow structures on altering the bed shear stress and UXO threshold of motion. These aspects are a first step to inferring the importance of these physical processes on the sea bed. Results may inform military stakeholders on the potential for UXO motion and transport and how to avoid undesired response through modifications of ship trajectories/maneuvers.

The project team will satisfy the objective of this project through a combination of laboratory-scale experiments, theoretical modeling, and field measurements. Experiments will include generating unsteady flow structures near a sediment bed characteristic of maneuvering ships in port; flow measurements will be made using stereoscopic particle image velocimetry and optical measurements will be used to assess particle suspension. Initial field trials will occur at the University of Delaware Marine Operations Station. A docked vessel will provide the prop wash while subsurface and bottom mounted sensors will measure the turbulent flow field and sediment suspension.

These results will directly benefit the Navy and the Department of Defense through knowledge of the unexpected forces prop wash may deliver to the seabed during berthing operations; the potential to exhume and/or transport munitions, and possible strategies to avoid undesired munitions transport. The first aspect of the problem is to quantify the hydrodynamic characteristics. This aspect will develop the understanding of the dominant flow features of maneuvering vessel prop wash, including turbulent and large- scale coherent motions, which features are responsible for sediment suspension, and how these features may lead to motion for UXO.

(Anticipated Project Completion - 2025).