Flutter analysis of a large aircraft model for wind tunnel tests

In the framework of the GRA low noise domain, the WENEMOR project was launched to carry-out aero-acoustic measurements on a wind tunnel test model representative of different aircraft configurations equipped with rear-fuselage open rotor systems, operating in both pusher and tractor modes. Due to the large scale of the test model (1:7.5 of the actual dimension), to its elasticity and to the fully powered propulsive system, it was considered mandatory to address aeroelastic instability analyses in order to assure tests safety. Rational approaches were implemented in order to simulate the effects induced by variations of design stiffness and damping values, especially for the engines/pylons connection; reliable aeroelastic models and advanced computational strategies were properly implemented to enable fast flutter analyses covering several configuration cases in terms of power plant installation and tail empennages layout. Flutter and divergence clearance was finally demonstrated up to four times the maximum flow speed expected during wind tunnel test campaign.