Aerodynamic deployment mechanism of Vortex Generators with innovative actuators based on “Smart” materials

This PhD thesis focuses on the numerical analysis of an adaptive vortex generator actuated by shape memory alloy (SMA), its structural feasibility, and the definition of a dedicated experimental validation campaign. Vortex generators are small aerodynamic devices designed to improve the performance of an aircraft wing by controlling the boundary layer, reducing flow separation phenomena, and enhancing overall lift and drag characteristics. Within the RADAR project, "contRollo Attivo Del flusso AeRodinamico," funded by the Greening PRORA 662 program, the goal was to develop vortex generators with innovative features. Specifically, the vortex generator developed is adaptive, meaning it is activated during flight phases where it significantly improves the aircraft’s aerodynamic performance. It is powered by an SMA actuator, which provides high performance in terms of actuation frequency and actuator miniaturization, preserving space. In addition to the previously mentioned benefits, the adaptive vortex generator performs two distinct aerodynamic functions. In high-speed flight conditions, the vortex generator is actuated in a spoiler configuration, fulfilling the load alleviation function. When actuated in a vane configuration, it serves as a stall avoidance device under high-lift conditions. Starting from Computational Fluid Dynamics (CFD) simulations using advanced turbulent models to accurately capture the complex physical phenomena associated with vortex generators, preliminary geometric dimensions were established before proceeding to the structural numerical model. The structural numerical model is nonlinear due to the presence of a material (SMA) that undergoes a phase change, from austenite to martensite and vice versa, due to heating. This results in significant deformation variations, leading to geometric nonlinearities and complex contact interactions. The study includes a parametric analysis of the dimensions, shape, positioning, and angle of incidence of the vortex generator, to identify optimal configurations for various operational conditions. Results demonstrate that the adaptive vortex generator can function during the flight phases in which it is activated, withstanding aerodynamic loads. Its mode of operation is highly innovative, as no similar devices in the literature can simultaneously fulfill both described functions. The AVG can adopt two shapes: symmetric, in the spoiler configuration relative to the airflow, and asymmetric, in the vane configuration. The action of the vortex generators can reduce induced drag without excessively penalizing parasite drag, thus improving the overall efficiency of the aircraft and reducing fuel consumption. Based on purely numerical simulations (CFD and nonlinear FEM), **a detailed design of the adaptive vortex generator has been developed, including considerations for its integration as a demonstrator in the PT1 wind tunnel at CIRA (Italian Aerospace Research Center). No physical prototype has been manufactured to date, and no laboratory or wind tunnel tests have been performed; instead, a comprehensive experimental plan has been defined for future validation of the numerical predictions. Keywords: Adaptive Vortex Generators, SMA Actuators, Active flow control, Vortex Generators Dual Functionality.