Fluid structure interactions of a rotor with flexible blades in water

Adding flexibility to rotating structures has been shown to improve their efficiency and reliability as well as their compliance to external flow perturbations (V. Cognet et al. 2017, 2020). Here, we investigate experimentally the problem of a propulsive rotor submerged in water with flexible blades in both spanwise and chordwise directions : when subjected to an incoming flow, the blades bend upstream and twist. We report measurements of both forces and associated blade deformations and give predicting scaling laws. A simulation of the full system using blade element momentum theory shows good agreement with the experiments. This simulation also reveals the existence of regions in the parameter space where the efficiency of flexible blades outperforms that of rigid ones.