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Session: Low/high order methods 2
Session starts: Thursday 20 June, 11:00
Presentation starts: 11:30
Room: Room 1.6

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Michael Pitzal (Institute of Aircraft Propulsion Systems, University of Stuttgart)
Johann Groß (Institute of Aircraft Propulsion Systems, University of Stuttgart)
Patrick Kopper (Institute of Aerodynamics and Gas Dynamics, University of Stuttgart)
Andrea Beck (Institute of Aerodynamics and Gas Dynamics, University of Stuttgart)
Malte Krack (Institute of Aircraft Propulsion Systems, University of Stuttgart)

Abstract:
The motivation for this work originates from an experimental campaign of an aero-elastically unstable NACA 0010-65 airfoil. Two configurations of the elastically suspended uniform wing were considered, one without and one with impact absorbers. In the former configuration limit cycle oscillations (LCO) saturated by nonlinear aerodynamic forces occurred, as well as coexisting solutions on different amplitude levels for the same flow velocity. In the latter, the impacts dissipate enough energy to significantly reduce (or almost annihilate) the vibration level in the analyzed flow velocity range. In this work we present a nonlinear FSI method, which accurately predicts both LCO and flutter suppression by impact absorbers in accordance with measurements. To this end, strong coupling between fluid and structural dynamics is established in time domain, which is required to capture the complex vibration regimes. The computational domains are still treated separately, such that the proposed method is conceptually not restricted to any particular choice of CFD or structural dynamics solvers as well as modelling approaches. For this particular case, we obtain the fluid dynamics using 2-dimensional Euler equations, solved by Discontinuous Galerkin Spectral Element Method framework FLEXI (written in FORTRAN). The mechanical system (implemented in MATLAB) is described by rotational and stroke motions of the airfoil while the contact interaction of impact absorbers with the airfoil is approximated using the Hunt-Crossley model. Data exchange between the two computational domains is realized via Python. To modern aircraft, wing flutter denotes one of the major design constraints. This work contributes to accurate prediction of wing LCO and development of effective flutter suppression devices, which are indispensable for the increase of engineering design space and, thus, efficiency of future aircraft.