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Modelling and simulation of gust and atmospheric turbulence effects on flexible aircraft flight dynamics

Castells Marin, Pau. Modelling and simulation of gust and atmospheric turbulence effects on flexible aircraft flight dynamics. PhD, Dynamique des fluides, Institut National Polytechnique de Toulouse, 2020, 139 p.

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Abstract

The prediction of the aircraft response to gust and turbulence is of major importance for different purposes. Gust load analysis is an essential part of aircraft design and certification. The effect of gust and turbulence on aircraft flight dynamics is also of interest. Models able to capture relevant effects at these conditions in early design phases are essential in order to anticipate and assess the aircraft response and flight control laws in realistic atmospheric disturbances before flight test. This work proposes a modelling strategy to capture relevant physics when simulating the aircraft response to gust and turbulence for flight dynamics investigations. The model provides accuracy at a low computational cost as well as consistency with gust loads analysis enabling multidisciplinary design. The approach is based on the integration of a nonlinear quasi-steady flexible flight dynamics model with an unsteady aeroelastic model linearized around a nonlinear steady state. The gust-induced forces have a significant impact on aircraft flight dynamics. Low computing times are required to cover several flight conditions and aircraft parameters. A computationally efficient multipoint aerodynamic model, which captures both unsteady aerodynamic and gust propagation effects, is generated from linearized Computational Fluid Dynamics (CFD) simulations in the frequency domain. The model is identified through a rational function approximation allowing for time domain simulations. A reduced number of additional aerodynamic states is sufficient to capture the main effects at low frequencies for flight dynamics analysis. The impact of dynamic flexibility on the response is also evaluated. Only the most energetic flexible modes are retained to reduce the number of states and ensure a low computation time. The approach is applied to simulate the vertical and lateral response of a passenger aircraft to theoretical disturbance profiles as well as realistic atmospheric turbulence at different flight conditions. Aerodynamic nonlinear effects, such as local stalls due to shock motion, in transonic conditions may appear. The linearized model is able to capture the global aircraft response at these conditions with low amplitude shock motions. Results are compared and validated with a CFD simulation based approach, coupled with a structural dynamics and flight mechanics solver. Measures from flight test are also used to assess the modelling approach. The effect of uncertainties on the response is analysed, in terms of the turbulence variation along the wingspan. Simulation results show that relevant aerodynamic effects due to gust and turbulence are captured in the frequency range of interest for flight dynamics investigations.

Item Type:PhD Thesis
Uncontrolled Keywords:
Institution:Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
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Research Director:
Braza, Marianna
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Deposited On:30 Mar 2021 13:17

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