Neuro-fuzzy-based reduced-order modeling for aerodynamic loads computation at high-speed buffet buffeting

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The accurate aerodynamic loads determination at the limits of the aircraft’s flight envelope is essential for reducing uncertainties within the design process and to yield optimized structures with respect to mass and stiffness distributions. The overall goal of this subproject within the research group FOR 2895 is, therefore, to develop a class of neuro-fuzzy-based reduced-order models (ROMs) that can be used for efficient load computation and analysis at transonic buffet/buffeting. These models will be thoroughly investigated concerning their accuracy, robustness and sensitivity against variations of Mach number, Reynolds number and angle of attack. Therefore, the results of the reduced-order models will be evaluated in comparison to experimental and numerical reference data. Particular challenges arise for the training process of the ROMs, which must be adapted to the dominating flow physics effects in order to be able to reproduce the frequency and amplitude related characteristics of the unsteady aerodynamic loads with sufficient accuracy. Hence, the transient aerodynamic load characteristics of a realistic transport aircraft configuration (XRF-1) under high-speed stall conditions can be recorded. With regard to the ROMs, the present subproject focuses on neural networks (“Multi-Layer Perceptron Network”, “Long-Short-Term Memory Network”, “Convolutional Neural Network”), which are used to map unsteady aerodynamic loads as a result of stochastic shock motions combined with local flow separation, thus, representing strongly nonlinear interactions. In the first project phase, it was possible to achieve results of very good accuracy relative to the reference data. This modeling will be continued in the second project phase and supplemented by an extension to consider the influence of vibrations on the flow-physical mechanisms. These investigations are motivated, among others, by the fact that the pressure spectra measured for the wind tunnel model in the ETW showed peaks at characteristic wing structural eigenmodes. Additional experiments in the ETW with targeted excitation of structural vibrations should provide further data on this. The influence of superimposed vibrations on the buffet scenario is thus analyzed by experimental and numerical simulations and ROM methods conditioned by them. In addition, for a further detailed analyses calculations in the form of one-way and two-way couplings for the structural response are carried out in order to represent the dynamic aeroelastic system and, thereby, to develop ROM methods for the coupled system with regard to structural dynamics analyses.