Qualitative and quantitative study about hull-propeller interaction for an X-fin AUV by different propeller models

This study is aimed at using fully viscous RANSE simulations in StarCCM+ with the use of the SST k-$\omega {-} \gamma$ transitional model to determine the effective wake of the propeller behind an axi-symmetric AUV hull. This low drag hull design, named the DIVE 2020E, was optimized optimized for its cruise speed to facilitate laminar flow up to a favorable axial position before naturally transitioning to turbulent flow. The flow characteristics are to be described qualitatively in terms of transition, vortex formation, interaction of flow around appendages, and acceleration through the propeller. The propeller, chosen from the Wageningen-B series is modelled in full (as a rotating body) and as a momentum source. The longitudinal position of the propeller is chosen in such a way that the thrust deduction is minimized. The effective wake and efficiency are calculated for each method of propeller modelling, namely the rotating-propeller method and the momentum-source method. The nominal wake, effective wake, thrust deduction, and effective inflow obtained for the two different models are compared to highlight the applicability of these methods to study the optimum propeller longitudinal positioning and sizing. It is observed that the implementation of this procedure with a virtual disc is not sufficiently accurate, since an reduction of about 10% in thrust deduction fraction and 10% in effective wake fraction is registered with respect the rotating propeller model.