Mat_Saad_whole_thesis.pdf (7.38 MB)
The hydrodynamic effects on a smaller underwater body in close proximity to a larger moving body
thesisposted on 2023-05-27, 10:48 authored by Mat Saad, KA
Today's underwater vehicles are extensively used in the marine, offshore, and defence industries for a range of tasks, including surveillance, intelligence data gathering, and maintenance. The hydrodynamic interactions between underwater vehicles operating in close proximity were investigated to determine the interaction mechanism and quantify the influence of varying parameters on the interaction effects. During their mission, Unmanned Underwater Vehicles (UUVs) are sometimes required to operate in close proximity to larger vehicles or bodies that can create complex flow patterns adversely affecting the smaller vehicle. Due to significant differences in size and speed, the latter is required to navigate through rapidly varying flow and pressure regimes, which can cause it to lose position and trajectory, resulting in mission failure and possible loss of vehicle. This project investigates these effects through numerical modelling and experimental work. This consists of modelling the behaviour of the smaller vehicle in close proximity to a larger vehicle using Computational Fluid Dynamics (CFD) in order to understand the interaction between the two vehicles under different configurations and conditions. Given that the smaller vehicle is more susceptible to the interaction effects, its behaviour is the focus of this thesis. The CFD results are validated through captive model scale experimental work in the Australian Maritime College towing tank using the forces and moments on the smaller vehicle due to the interaction. The work further investigates the issues involved in related numerical modelling and experimental techniques, and presents the approaches undertaken to address these issues. The research focuses on the hydrodynamic characteristics which are pressure distribution and flow regime generated between the two vehicles as they operate in close proximity to identify the behaviour and trajectory of the smaller vehicle. Once the interactions between the underwater vehicles are determined, the magnitudes and trends of the forces and moments action on the smaller vehicle as it moves relative to the larger vehicle are quantified. This enabled the establishment of a safe operational envelop for the smaller UUV to operate around the larger vehicle, including low risk options to approach and depart the latter.
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