Numerical investigation of a fleet of self-propelled AUVs

This paper investigates the influence of the propeller on the drag of twin self-propelled AUVs, firstly, to examine the fleet performance for various propulsive conditions of leading and following AUV and, secondly, to study the parametric influence of transverse separations and longitudinal offsets on the fleet’s drag. A series of CFD RANS-SST simulations have been performed at the Reynolds Number 3.2× 106 with a commercial code ANSYS CFX 12.1. Mesh convergence is tested and validated with experimental and empirical results. The RANS-HO and RANS-UT propeller models are selected to estimate the time averaged thrust and torque of the propeller. The results show that the self-propelled vehicles experience an additional drag which is dominated by the thrust distribution of the propeller rather than torque. The drag of the following AUV is increased due to the upstream propeller, defined as a propeller race deduction. For the parametric studies, the results show that increasing the spacing results in a lower drag. The two sources of self-propelled drag increment are the viscous interaction and a direct result of proximity to the propeller race upstream. The result highlights the importance of considering both thrust deduction and any propeller race deductions when calculating the propulsive power consumption.