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This thesis continues previous work conducted on the interactions between a single propeller unmanned underwater vehicle (UUV) and marine vegetation. It attempts to define the asymmetric behavior of entanglement between a single, shroud-less propeller and synthetic eelgrass. A Disposable Reusable Expeditionary Warfare Underwater Vehicle (DREW UV), designed as a low-cost testing vehicle, was fixed at various test conditions in a towing tank. A four-factor full factorial design of experiments that varied lateral separation, depth, vehicle speed, and whether the eelgrass was on the port or starboard side of the vehicle was used to evaluate how these factors changed the likelihood of entanglement with a single strand of eelgrass. Each factor’s impact was assessed as it pertained to which side of the vehicle the eelgrass was on. The tests revealed that significant asymmetry exists in the behavior of entanglement for a single propeller UUV based on the side of passage. The likelihood of entanglement is further reduced or increased based on the other variable factors. Thus, the asymmetry that exists does so on a scale. Certain test conditions can exacerbate this asymmetry and should be given consideration when applied to operational usage. Future work includes further testing to increase fidelity in results, testing to understand the stochastic nature of occlusion events, and work to explore the possibly non-linear effects of propeller flow pattern on the likelihood of entanglement. Lieutenant, United States Navy Approved for public release. Distribution is unlimited. |
