An alternative simulation approach for the ONERA aerodynamic model and its application in the nonlinear aeroelastic analysis of slender wings with pylon-store system

Abstract

The ONERA aerodynamic model is a nonlinear aerodynamic model which includes the effects of dynamic stall. With the strip theory, the ONERA model is usually used in the aeroelastic analysis of slender wings. To the classical approach for the ONERA model, the circulatory and nonlinear parts are all described by using aerodynamic elements and the simulation cost may be very high. In this paper, an alternative simulation approach is proposed to simplify the calculations for the ONERA model, in which the circulatory part of the ONERA model is solved analytically by using Duhamel integral method. In this way, the corresponding aerodynamic loads can be directly expressed in the modal space of the wing motion through only introducing two additional variables. For a slender wing model, the new simulation approach is used to analyze its nonlinear aeroelastic responses. In the simulation, the number of the state variables for the system using the proposed approach is reduced modestly comparing with that using the classical approach. In addition, for a slender wing with a pylon-store system which includes a free-play gap, both the proposed approach and the classical approach with the same number of aerodynamic elements are used to analyze the nonlinear dynamic behaviors of the system. Simulation results are given to show that the pylon-store system with a free-play gap can lead the occurrence of sub-critical Hopf bifurcation for a slender wing. Additionally, some nonlinear dynamic phenomena about the wing-pylon-store system are observed by using the new approach. But these phenomena cannot be predicted by employing the classical approach with the same number of aerodynamic elements used in the new approach. The peak of the post-critical responses obtained from the classical approach are larger than those obtained from the new approach in most range of free-stream velocity. The nonlinear flutter velocity predicted by using the classical approach is lower than that predicted by using the new approach.