Investigation on the hydrodynamic load fluctuations through passive flexible leading edge

Abstract

The study presents a numerical investigation of two-dimensional partly flexible plate dynamics. The structure is immersed in a turbulent fluid flow with a Reynolds number based on its chord of 104. The plate is animated by a forced pitching movement. The flexibility effects of the plate's leading edge are analyzed, as it deforms under the hydrodynamic loads. The fluid–structure interaction effects are considered by solving a coupled problem using a strong implicit procedure. Both fluid and solid dynamics are solved. The numerical results of the present study are validated with experimental ones with a good agreement between both approaches for the lower reduced frequencies. Differences are observable for high frequency that could be imputable to the three-dimensional aspects of the experiment. It has been shown that with an appropriate choice of the rigidity of the structure, it is possible to mitigate the unsteady load fluctuations without affecting the load mean values too much. Indeed, at low pitching frequency (drag mode), the leading-edge vortex generation is impacted by the flexible leading edge. As a result, it tends to decrease the hydrodynamic force fluctuation amplitude without really impacting the mean force value. Conversely, at high pitching frequency (propulsive mode), it was found that a flexible leading edge tends to increase both the magnitudes of the hydrodynamic forces and their mean values. Finally, it is shown that the load fluctuation mitigation, or amplification, is maximum for a specific flexibility value depending on the pitching frequency.