Real-time extraction of hydrodynamic flow characteristics using surface signatures

This paper describes a simple and robust engineering approach for the real-time sensing and monitoring of unsteady hydrodynamic loads and moments. Innovative flow diagnostics techniques are used to extract critical flow phenomena such as the state of the boundary layer (laminar, transitional, or turbulent), leading-edge stagnation point (or attachment line), flow separation and reattachment, and vortex pattern and their dynamic characteristics from surface hot-film signatures obtained with multielement, micron-thin surface hot-film sensors operated by a bank of constant voltage anemometers. Unsteady hydrodynamic loads and moments are then obtained as a function of the instantaneous locations of the critical surface signatures. Test results from a few recent experiments are described. The heuristics approach presented here will be useful for the development of closed-loop active control system for advanced autonomous underwater vehicle designs with biologically inspired smart actuators.