Eventos Anais de eventos
DINAME 2017
XVII International Symposium on Dynamic Problems of Mechanics
STRUCTURAL NONLINEARITIES EFFECT ON AEROELASTIC BIFURCATION PHENOMENA IN AIRFOILS
Submission Author:
Flavio D. Marques , SP , Brazil
Co-Authors:
Daniel de Almeida Pereira, Carlos Renan dos Santos, Flavio D. Marques
Presenter: Daniel de Almeida Pereira
doi://10.26678/ABCM.DINAME2017.DIN17-0012
Abstract
Nonlinear aeroelastic behavior can be originated from aerodynamic and/or structural dynamics, therefore leading to several problems such as instabilities, limit cycle oscillations, bifurcations, and chaotic behavior. The objective of this work is to analyze and identify the dynamic response of a typical aeroelastic with structural hardening and free-play nonlinearities acting simultaneously. The effect of hardening corresponds to a smooth nonlinear increasing in restoring structural loading for a given displacement. This effect is modeled here by means of rational polynomial function, while the free-play is represented by hyperbolic functions combination. Aeroelastic responses are analyzed from computational and experimental results. The numerical model is based on the classical theory for the linear unsteady aerodynamics with corrections for arbitrary motions coupled to typical aeroelastic section model. Hopf bifurcations are identified and diagrams of amplitudes versus airspeeds are used to investigate the conditions in which the system is supercritical or subcritical. Higher-order spectra analysis is also used to check on frequency couplings, thereby allowing the identification of quadratic- and cubic-like nonlinear behavior. The study of the phenomena associated with the hardening, free-play and their intensity variation effects provide ways to mitigate or circumvent any undesired responses to those behaviors. This contributes to determine safety margins for aircraft even with these nonlinearities, as fully linear systems represent major challenges to achieve, and results in very high costs.
Keywords
Aeroelasticity, subcritical bifurcation, hardening, free-play, higher-order spectra analysis
