Insights on the unsteadiness and stall effects on the characteristics and responses of continuous wing-based systems

Abstract

The effects of the aerodynamic loads on continuous wing-based systems can be represented using a quasi-steady or a fully unsteady reduced-order modeling. Frequently, the quasi-steady formulation is used to model the aerodynamic loads at small reduced frequency values. This approximation, unlike the unsteady formulation, does not account for any lag between the unsteady oscillations and its effect on the aerodynamic loads which might lead to over or under predicting some crucial information related to the system studied, particularly concerning the onset of flutter or type of instability. To this end, in this effort, a comparison of the effects of different aerodynamic formulations on a wing-based system is conducted. A linear analysis considering the influence of each noncirculatory term in both formulations is inspected individually, and the results generated from both aerodynamic formulations are compared while depicting the effects of the structural damping on the linear flutter speed and frequency. A nonlinear analysis is then performed to investigate the stall effect on the system’s response as well as the impacts of different nonlinearities including inertial and geometric. The system’s behavior is examined using higher modes in the Galerkin discretization to make sure that it is accurately modeled and that the number of modes selected does not fail to correctly portray its aeroelastic response. The results of this study show the importance of using the unsteady fluid–structure interaction with stall modeling for continuous wing systems even for small angles of attack and reduced frequency values.