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Computational Transonic Flutter Solutions for Cranked Wings by the Direct Eulerian-Lagrangian Method

  • Author(s): Mellquist, Erik Charles
  • Advisor(s): Bendiksen, Oddvar O
  • et al.
Abstract

In this dissertation, a three-dimensional computational aeroelastic simulation for cranked, highly-swept wings is developed, and solutions are presented for several wing models. The computational model is a fully nonlinear coupled fluid-structure simulation based on the Direct Eulerian-Lagrangian coupling methodology. The wing is modeled using nonlinear modified von Karman plate finite elements. Large deformation is accounted for through the use of element-attached local coordinate systems referenced to a single global coordinate system. The fluid is modeled using the mixed Eulerian-Lagrangian formulation of the classical Euler equations and is discretized using a Galerkin finite element approach on an unstructured tetrahedral mesh. The fluid and structural models are coupled by the Direct Eulerian-Lagrangian method where the finite-element shape functions and the local element coordinate systems are used to describe the fluid-structure boundary without approximation. Time synchronization and spatial accuracy are maintained to ensure accurate exchange of energy between the fluid and the structure.

The computational solutions exhibit multiple types of aeroelastic response including transonic limit cycle flutter at a wide range of dynamic pressures, subsonic and supersonic bending-torsion flutter at higher dynamic pressures and a wide range of Mach numbers, and limit cycle oscillation dependent on both Mach number and angle of attack. Shock motion dependent on wing deformation is shown to play a major role in determining the response of the wings, and, depending on the flow conditions, can either stabilize or destabilize the response. Results from the simulations correlate closely with observed wind tunnel test responses.

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