Aeroelastic analysis of propeller blades at stall flutter onset

Abstract Aeroelastic analyses are part of the design of modern propeller blades. Most of the time, advanced numerical simulations are used, involving computational fluid dynamics. However, the coupling between fluid and structure may be missing. In this paper, two coupled fluid-structure interaction methods are presented, namely the modal time-marching and the quasi-static approach. An in-house aeroelastic tool, analysing an in-house blade design, is used. A limited number of experiments are available, and this was alleviated using new experiments as part of the Numerical and Experimental Study of Propeller Aeroelasticity project. In this work, 3D finite element models (FEM) were used to represent the blade structure. Time-marching and quasi-steady results were compared, and this is the first time that this is reported in the literature. It was found that regardless of the differences in the aerodynamic loads between time-marching and quasi-static computations, the final blade deformations were comparable. Time-marching computations using a modal representation of the blade, obtained from 3D FEM, showed that the blade deformation and vibration were driven by the stalled flow. This observation was verified by comparing the blade response with the flow off-the-blade. The harmonic content of the results includes the propeller blade passing frequency and its natural frequencies, but also additional frequencies related to the flow shedding and vortical content of the stalled part of the blade. To the best of our knowledge, this has not been reported in the open literature.