Gust Encounter of a Supersonic Fighter Aircraft using CFD Methods

Kurzfassung

The gust encounter of a supersonic fighter aircraft is investigated with the CFD code SU2 and the aerodynamic panel methods VLM and ZONA51. The interaction of the elastic aircraft, the flight controller and the gust is captured in a closed-loop time domain simulation. The comparisons show a moderate agreement between aerodynamic panel methods and CFD in terms of section loads, which has multiple reasons: first, the two aerodynamic methods yield different pitching moment characteristics, which have an influence on the flight mechanical reaction of the aircraft and the reaction of the flight controller. Second, due to the increase of the effective angle of attack during the gust encounter, vortices develop, which are not present in the horizontal level flight condition. Because of the large suction peaks due to the vortices, the surface pressure distribution changes significantly, an effect that is missed completely by the aerodynamic panel methods. The section loads predicted by the CFD based approach are higher, which eventually influences the structural sizing of the aircraft. Also, there is a significant structural dynamic reaction, which shows that for fighter aircraft, a transient gust analysis including structural elasticity is essential for the aircraft design.