Dynamic Response and Stability of Flexible Hydrofoils in Incompressible and Viscous Flow.

Abstract

It is important to understand and accurately predict the static and dynamic response and the stability boundary of flexible hydrofoils to ensure their structural safety, facilitate the design and optimization of new and existing concepts, and test the feasibility of using advanced materials and control concepts. In particular, with recent advancements in material and computational modeling and design, it is possible to take advantage of advanced materials and the fluid-structure interaction response to improve the hydrodynamic and structural dynamic performance of flexible hydrofoils. The study of aeroelasticity has been the focus of aerospace and wind engineering structures, where the fluid density is much smaller compared to the solid density, and hence the effects of fluid inertia or damping forces are relatively small. However, for the hydroelasticity of marine and naval structures, the effect of fluid inertia and hydrodynamic damping can be much greater than that of solid inertia and damping, and the loading can be much more complicated due to viscous effects, hydrodynamic cavitation, and proximity to the free surface. As interest in maritime applications of lightweight, flexible hydrofoils increases, understanding the flow-induced vibration response and stability becomes more important to ensure structural safety and to optimize performance and control. Hence, the objectives of this dissertation are the following: 1) to derive and validate the FSI response and stability boundary of flexible hydrofoils in incompressible and viscous flow; 2) to investigate the influence of inflow velocity, angle of attack, and relative mass ratio on the flow-induced vibrations of flexible hydrofoils; and 3) to investigate the influence of the flow-induced bend-twist coupling of flexible hydrofoils.