Scattering and Directionality Effects of Noise Generation from Flapping Thrusters Used for Propulsion of Small Ocean Vehicles

Flapping-foil thrusters are systems that operate at a substantially lower frequency compared with marine propellers and characterized by much smaller power concentration. These biomimetic devices able to very efficiently, offering desirable levels of thrust required for the propulsion small vessels or autonomous underwater vehicles (AUVs), can be used standalone augmenting ship in waves, alleviating generation noise its adverse effects on sea life, particularly mammals. In this work, we consider flapping foils arranged neighborhood above including scattering hull, which, addition free-surface seabed effects, significantly contribute modification characteristics acoustic field. A Boundary Element Method (BEM) is developed treat 3D problem domain forced monopole dipole source terms associated Ffowcs Williams Hawkings (FW-H) equation. Numerical results presented selected cases illustrating hull geometry properties, as well surface important determination directionality generated affect propagation ocean environment.