Nonlinear aeroelasticity
Nonlinear aeroelasticity is a subject of high interest and activity. In this paper the authors aim is to provide a faithful account of the topic with an emphasis on key ideas and results which demonstrate our community's current theoretical, computational and experimental capabilities. The particular results and methods described will reflect the authors' knowledge and experience, but the authors have made an effort to be comprehensive in terms of ideas and representative results from others. The paper provides a discussion of generic nonlinear aeroelastic behavior especially as it relates to limit cycle oscillations (LCO); then the important studies that come from flight experience with LCO are noted which have stimulated additional research. A summary is provided of the primary physical sources of fluid and structural nonlinearities that can lead to nonlinear aeroelastic response. An account of unsteady aerodynamic models is given as well as a critique of the results obtained to data via various methods. The authors provide correlations between theory and experiment or alternative theoretical models. Flutter boundaries and limit cycle oscillations are each considered. For limit cycle oscillations (1) airfoils with stiffness nonlinearities, (2) delta wings with geometrical plate nonlinearities. (3) very high aspect ratio wings with both structural and aerodynamic nonlinearities, (4) nonlinear structural damping and (5) aerodynamic flows of large shock motions and flow separation are each discussed. A brief discussion is also made of recent studies of active control of nonlinear aeroelastic systems. The authors conclude with a summary of major lessons learned by the research and development community to date and offer a few suggestions for future work.
