Numerical investigation of a pair of self-propelled AUVs operating in tandem

This paper investigates the influence of the propeller race on upstream and downstream self propelled AUVs. Initially simulations of a self-propelled hull are performed at the Reynolds Number 3.2x10^6 with software commercial RANS code ANSYS CFX 12.1, utilising a body force model to replicate the impact of the propeller utilising momentum source terms. This is then extended to consider a fleet of two self-propelled vehicles operating at a range of longitudinal offset and transverse separations. The results highlight that operation in close proximity to another self-propelled vessel has a significant impact of both the flow around the hull and drag experienced by the vehicle. A propeller race deduction is proposed to account for the increase in vehicle drag due to the propulsors of other vehicles. The propeller race deduction is dependent upon both longitudinal and transverse separation. From a vehicle or mission design perspective, it is important to correctly understand the true propulsive energy budget of the vehicle and its impact on both range and endurance. This study highlights the importance of considering both thrust deduction and any propeller race deductions when calculating the propulsive power consumption of an individual or fleet of vehicles.