Fuel sloshing-induced effects on the dynamic response of a scaled research wing demonstrator

Fuel sloshing inside aircraft wing tanks is not currently considered as a means of passive loads alleviation due to the lack of maturity of modelling tools and overall understanding of vertical sloshing. In this work, a scaled research wing demonstrator is presented, designed for the study of fuel sloshing inside an aircraft wing-representative model. An experimental campaign was conducted to examine the impact of fuel sloshing on the vertical dynamics of a scaled aircraft wing demonstrator, investigating the influence of excitation amplitude, filling level, baffle geometry, spanwise liquid position, and dihedral angle. It was found that the sloshing of the liquid in the fuel tank causes significant energy dissipation following step release excitation, maximized in the 40-60% filling range depending on the dihedral angle. The sloshing-induced damping also varies with the amplitude of excitation, with maximum added damping ratio of 0.038 achieved earlier in the motion at larger excitation amplitudes. The spanwise distribution of the liquid was found to have the strongest effect on the sloshing-induced damping, with the baffles' main impact being through the compartmentalization of the tank. Solid baffles that maintain favorable liquid distribution can increase the damping effect, while perforated baffles are not as effective. This work indicates that by considering the fuel dynamics rather than the fuel equivalent dry mass during the aircraft wing design, the net damping may be increased, leading to lighter wing structure designs.