Assessment of Body-Freedom Flutter for an Unmanned Aerial Vehicle

Abstract

The flutter characteristic of a highly swept flying wing unmanned aerial vehicle (UAV) is studied for the DLR-F19 concept. The compact geometry, based on the SACCON configuration, raises the question whether a coupling between rigid-body and elastic modes, known as “Body-Freedom Flutter” (BFF), is relevant for this configuration to be a critical flutter phenomenon. The important modes contributing to the various flutter mechanisms are identified by means of the average power of the modal unsteady aerodynamics. Furthermore, aerodynamic methods based on potential flow theory (MSC.Nastran DLM and ZAERO ZONA6) and the Euler equations are used to assess the accuracy of fast aerodynamic methods for flutter point prediction of this particular configuration at a low transonic Mach number of 0.8. The BFF phenomenon is further examined by modifying the mass and stiffness distributions of the configuration.