Coupled CFD-CSM Analyses of a Highly Flexible Transport Aircraft by Means of Geometrically Nonlinear Methods

Abstract

The ever lasting race towards increased efficiency in the aircraft industry has resulted in excessively slender and lightweight airframes. Utilising the anisotropic characteristics of specifically tailored composites is one key driver, enabling structural concepts which were impossible a few decades ago. The results are highly flexible aircraft structures, pushing geometrically linear methods to their limits. One example of such a concept is the Boeing 787 which reaches wing tip displacements of approximately 10 % of the wing half span already during cruise flight. Thus, loads and flight dynamics analyses have to be developed which are accurate in the context of large deflections. By utilising a coupled CFD-CSM analysis in combination with a highly flexible long range jet transport model, this paper aims to establish the groundwork for a high fidelity geometrically nonlinear loads framework. In this publication, a general methodology to compute static manoeuvre cases with deflections of up to 25 % is presented. Furthermore, by computing rigid and elastic polars as well as calculating pull up and push down manoeuvres, the differences between geometrically linear and nonlinear simulations are illustrated with respect to aerodynamic parameters, cut loads, and strains.