Nonlinear Numerical Flight Dynamics of Flexible Aircraft in the Time Domain by Coupling of CFD, Flight Mechanics, and Structural Mechanics

Abstract

Dynamic analysis of flexible aircraft typically involves the separation of rigid body and structural dynamics. This approach is justified, if an adequate distance between the frequencies of the elastic and the flight mechanic modes is present. For aircraft structures characterized by relatively low elastic frequencies (e.g. large passenger aircraft or sailplanes) the combined calculation of the coupled rigid body and structural dynamics becomes evident and the setup of an integrated aeroelastic model of the aircraft is necessary.

This article describes the derivation of the integrated aeroelastic model, composed of governing equations for the translational and the rotational motion. A modal approach is used for the calculation of the elastic deformations of the aircraft, therefore using unconstrained free-free vibration modes from a finite-element analysis. The aerodynamic forces are calculated by a CFD solver. The integration of all involved disciplines is finally done via a weak coupling approach applying a CSS (Conventional-Serial-Staggered) algorithm.