Dynamic Nonlinear Aeroelastic Analysis of the Joined Wing Configuration

Abstract

The unsteady vortex lattice method (UVLM) is coupled via OpenFSI with MD Nastran's dynamic nonlinear structural solver to study the aeroelastic response of the joined wing configuration in a subsonic regime. Initially, a number of static nonlinear structural analyses are performed on the nonlinear beam model to investigate the nonlinearities associated with the structure. The primary reason for the investigation of the structural nonlinearities is to make intelligible the aeroelastic response of the structure. After a successful validation of UVLM.OpenFSI, a panel based aerodynamic model is splined with the structural model for accurate transfer of forces and displacements at every time step via OpenFSI. A new boundary value problem is solved for the modified aerodynamic model at every time step. Evolution of the wake and its aerodynamic effects are well accounted for. Time domain responses of the lift generated by the joined wing configuration under various loading conditions is obtained. The flutter boundary of the joined wing configuration is calculated by interpolating between the dampings values evaluated for stable and unstable time domain responses. Also presented is the time domain response of the joined wing configuration when subjected to external excitations, predicting the onset of flutter and the post flutter behavior.

Phenomenology of Nonlinear Aeroelastic Responses of Highly Deformable Joined-wings Configurations

“…Unfortunately, is it not possible to automatically extend this approach to the aerodynamic forces, since the simultaneous dependence on acceleration, velocity and displacement does not make straightforward the use of a unique convex combination: it would be an open question which value between α f and α m should be used on this regard. In this effort, both the option t+α f ∆t P ext , namely: (15) and the one previously introduced in eq. (11), have been used.…”

“…Very few results have been proposed for different layouts of Joined Wings [15], and a lack of understanding of the physics of the phenomenon is evident: additional studies are then necessary.…”

“…Recalling section B, there were different options for the time integration, leading to different options for the evaluation of the aerodynamic contribution, namely eqs. (15) and (11). With the expression outlined in eq.…”

“…To the best of authors' knowledge, nonlinear aeroelastic dynamic analysis was pursued only in a few efforts, i.e. references [14,15]. The first of these preliminary studies showed how the flutter speed prediction varied when using a nonlinear modelling of the structure, whereas the second studied a limit cycle oscillation.…”

Challenges, Ideas, and Innovations of Joined-Wing Configurations: A Concept from the Past, an Opportunity for the Future

“…Reference [21] introduced a framework (OpenFSI) to couple the unsteady vortex lattice method (developed at Virginia Tech) and MD NASTRAN. The wake roll-up was modeled and the compressibility effects taken into account with corrections (for the steady case using Prandtl-Glauert correction, for the unsteady case Morino's approach).…”