Understanding the feasibility of vectored thruster using CFD as a design tool

Rishika Patel, Lakshmi Madhavan Miller, Daniel J. Stilwell

Abstract

This study explores the feasibility of integrating a gimbaled thruster into the VT-690 Autonomous Underwater Vehicle (AUV). Typically, AUVs are equipped with either open or ducted propulsion systems, providing either self-propulsion or active control. Introducing a gimbaled, vectored thruster offers an advanced form of active control that removes for multiple moving fins. Using computational fluid dynamics (CFD) as a design tool, this study evaluates the feasibility of this significant design modification. The research involves analyzing forces and moments generated by the vehicle when equipped with a ducted momentum source, and comparing it to those produced by stationary and moving fins. This design shift introduces dynamic factors, such as maneuverability and stability, which are complex to assess solely through CFD. Results from these simulations are used as quantifiable surrogates to determine the design feasibility of replacing fins with a gimballed thruster. The scope of this study does not consider the mechanical implementation of the vectored thruster. Maneuverability and stability are critical to the operation of AUVs. Fins are crucial in achieving these goals. Moving fins are used for deflection and thus direct generation of turning forces and moments along all three axes. Fixed fins are typically offer advantages in flow and stability. Replacing such a system of fins with a capable vectoring thruster configuration is desirable due to simplicity in construction and efficiency and maneuvering. There is considerable interest in using gimbaling or vectoring thrusters to reduce the reliance on mechanical components like moving fins. This approach eliminates the weight, cost, and wear associated with such parts, ultimately reducing the risk of failures by minimizing the number of moving components.
Therefore, this research compares the forces acting on the craft, including those generated by moving and fixed fins, with those produced by a deflected, ducted thruster. This comparison helps assess the effectiveness of vectoring in place of fins.

Acknowledgement
This effort is funded by Office of Naval Research.