Sweep and anisotropy effects on the viscous hydroelastic response of composite hydrofoils

摘要

Composite materials have become prevalent in hydrofoil design due to their favorable characteristics. Both material anisotropy and planform sweep are factors that affect hydrofoil performance. However, the interplay between these two factors has not been studied systematically. This paper investigates this interplay in the viscous hydroelastic response of linearly tapered composite hydrofoils with a modified NACA 0009 cross-section using high-fidelity hydrostructural simulations. The simulations are based on a Reynolds-averaged Navier-Stokes solver coupled to a structural finite-element model. Both sweep and off-axial fiber layup reduce the bending-mode natural frequencies due to the decrease in bending rigidity. Sweep reduces the form drag by suppressing trailing edge separation, but it can increase the lift-induced drag by causing the spanwise load distribution to deviate away from the ideal elliptical distribution. The spanwise load distribution can be tailored to reduce the induced drag and delay cavitation inception using sweep-induced geometric, material-induced bend-twist coupling, or both. Nevertheless, a poor combination of sweep and material configurations can accelerate static divergence, early separation, cavitation, noise, and material failures. Besides changing the structural response and resultant fluid-structure interaction, the material failure inception load and failure location depend directly on the fiber orientation due to the anisotropic characteristic of composites.