An aeroelastic coupled adjoint approach for multi-point designs in viscous flows

• Gekoppeltes adjungiertes Verfahren für den Navier-Stokes basierten aeroelastischen Mehrpunktentwurf

Abu-Zurayk, Mohammad; Gauger, Nicolas Ralph (Thesis advisor); Frank, Martin (Thesis advisor); Behr, Marek (Thesis advisor); Kroll, Norbert (Thesis advisor)

Als Manuskript gedruckt. - Köln : Deutsches Zentrum für Luft- und Raumfahrt (2016, 2017)
Book, Dissertation / PhD Thesis, Report

In: Forschungsbericht / DLR, Deutsches Zentrum für Luft- und Raumfahrt 2017-10
Page(s)/Article-Nr.: xii, 86 Seiten : Diagramme, IllustrationenReport number: DLR-FB-2017-10

Dissertation, RWTH Aachen University, 2016

Abstract

As the wing flies, its structural elasticity interacts with the aerodynamic loads and the wing deforms. This deformation influences the aerodynamic flow over the wing. Hence, besides employing high-fidelity flow equations, considering the structural elasticity is necessary for an accurate prediction of the wing aerodynamic coefficients. Wing shape optimizations that consider high-fidelity aeroelastic effects are computationally costly and therefore the gradient-based algorithms are suitable for them. This study presents an efficient approach for computing the gradients required for such optimizations. An existing viscous flow adjoint approach is extended to include the structural elasticity effects. The contribution of this work is, to differentiate the flow-structure coupling methods and to implement the coupled adjoint equations in order to use it within industrially relevant wing-shape optimizations. The advantages of this coupled aeroelastic adjoint approach are that it computes the gradients accurately and nearly independently of the number of design parameters engaged in the optimization, hence it is possible to use high number of design parameters. This allows high-fidelity multipoint optimizations within acceptable computational time. In this context, it is found that the adjoint approach is saving more than 80% of the computational cost when compared to the conventional finite differences approach for computing the gradients. After successfully validating the gradients obtained with the developed approach, four optimization scenarios are performed on a wing-body configuration in a transonic flow regime. The effects of considering several flight points as well as considering some rough weight constraint are tested and this latter constraint shows beneficial results for aerodynamics as well as the structure of the aircraft.