Application of Hydrodynamics and Dynamics Models for Efficient Operation of Modular Mini-AUVs in Shallow and Very-Shallow Waters

Abstract

LONG-TERM GOALSThe long-term goal of this research is to contribute to improvements in design and motion-control of small autonomous underwater vehicles, including multiple-vehicle operations and particularly for missions in wave-energetic shallow and very-shallow waters, based on rigorous dynamic and hydrodynamic analyses and modeling. OBJECTIVESThe objective of the research is to carry out nonlinear dynamics and hydrodynamics analyses of small and modular mini-AUVs and determine their vehicle-stability, -maneuverability and motion-response characteristics for a range of missions, vehicle-configurations and sea states, and thereby contribute to improving the efficacy and reliability of modular AUVs. APPROACHThe research investigates two main aspects of dynamics and hydrodynamics of underwater vehicles; namely, [i] determination of hydrodynamic forces on an underwater vehicle including effects of viscosity, large-amplitude body motion and surface waves, and [ii] analysis of motion response, stability and maneuverability of underwater vehicles subjected to the hydrodynamic forces. The hydrodynamic and dynamic simulations are carried out for a range of ambient and vehicle parameters, in order to identify key factors affecting the performance of underwater vehicles.Computationally efficient and robust algorithms have been specially developed for the present analyses. The hydrodynamic forces are computed by solving the governing nonlinear equations using finite-difference and boundary-integral methods. The inviscid nonlinear wave-AUV interaction problem is solved and wave-radiation and -diffraction forces determined using a boundary-integral method based on the mixed Eulerian-Lagrangian formulation [6][8] [10] . As, in the regimes of validity, linear and inviscid calculations are straightforward and economical, boundary integral methods based on simple source distribution and linearized boundary conditions have also been developed [8] . Approximate linear and inviscid methods, as that based on the Froude-Krylov method [7][9] formulated 1