A 3-D Unsteady Hydrodynamics Design Methodology for Underwater Vehicles and Appendages

Underwater vehicles, and particularly unmanned underwater vehicles (UUVs), are becoming increasingly identified as safe and cost-effective solutions for a wide range of applications including environmental monitoring, facilities and vessel inspection, and exploration, often in hazardous environments or conditions. To address the growing need for UUV operations in hazardous environments, designs of unconventional, mission-specific platforms are being investigated in larger numbers. Operational performance requirements, such as precise hovering and very low speed maneuvering in currents and under waves for in-shore operations, demand a vehicle capable of rapid response to a changing environment by production of the proper time-varying balance of lift and thrust. In these highly dynamic flow fields, standard steady drag and moment curves are not valid models. Also, standard semi-empirical methods for coefficient estimation based on linearized Taylor Series expansions are not available for these systems, as neither full-scale nor model-scale performance data exist, except possibly in the case of torpedo-like hulls. This lack of existing data and modeling capability for unconventional systems led us to pursue the development of a high-fidelity direct computational method as a starting point to inform the designs and estimate performance in a highly nonlinear flow regime.