Experimental and numerical investigation of the fluid-structure interaction on a flexible composite hydrofoil under viscous flows

This research investigates the fluid-structure interaction and hydroelastic response of a composite hydrofoil using an innovative joint experimental and numerical method. The main novelties are, first, the use of a state-of-the-art strain measurement technique, via a fully-distributed-optical fiber sensor directly embedded within the composite plies. This method allows for a finer representation of the structural deformations under hydrodynamic loading. Second, a tightly-coupled high-fidelity fluid-structure interaction numerical model taking into account the turbulent effects in the flow and the ply-by-ply modelling of the composite, is compared to the experimental results. A composite profile is specifically designed as a trapezoidal hydrofoil and is tested for moderate Reynolds number and pre-stall and post-stall incidences. High-speed imaging of the hydrofoil tip and vibrometer measurements are carried out to determine the experimental tip displacements and hydrofoil's vibrations. The numerical and experimental results show a very strong hydroelastic response, with a structural resonance even for low Reynolds numbers due to the high flexibility of the structure. Strong coupling of the fluid and the structure, with lock-in of the von Karman vortex-shedding to the structure for small incidences, and an excitation of the structure by leading-edge vortex-shedding for higher incidences, are also observed.