Flutter prediction correlations with wind tunnel measurements on a T-tail flutter mock-up

ifasd2024 Tracking Number 104

Flutter computations on a T-tail aircraft hold challenges as flutter behavior is significantly driven by specific aerodynamic phenomena. Interactions between tail surfaces have to be computed correctly to predict flutter accurately. Developments were performed at DASSAULT-AVIATION to improve in-house solvers for these specific configurations. To validate numerical tools, some reference experimental data are required. To do so a wind tunnel test mock-up has been designed and manufactured in the frame of CleanSky2 project in cooperation between DASSAULT-AVIATION, ONERA and RUAG. This mock-up was tested in 2016 for U-tail configurations. A second wind tunnel test campaign took place in 2022 in ONERA S2MA pressurized wind tunnel. The second campaign allowed testing different T-tail configurations and gathering data for subsonic, transonic and high transonic domains. Flutter curves have been measured up to the flutter point thanks to an efficient safety system that allowed reaching flutter boundary numerous times without structural damage. The tests, conducted up to Mach 0.925, have shown good repeatability leading to a high confidence in the measures. To help numerical restitution the model was extensively instrumented with pressure sensors, accelerometers and strain gauges. The mock-up dynamic behavior was measured through ground vibration tests, allowing the tuning of the Finite Element Model of the mock-up. Configurations tested consisted in several incidence settings of the horizontal tail plane to cover various lift forces and a dihedral effect. Both effects are of prime importance when computing flutter. Thus the need for validation of the numerical predictions for those effects. This paper presents correlations between experimental data and numerical computations. The methods used by DASSAULT-AVIATION for the numerical restitution are linearized Navier-Stokes CFD and enhanced Doublet Lattice Method - taking into account rolling, yawing and spanwise in-plane motion in addition to the regular pitching and plunging motions. Good correlations are obtained as depicted in Figure 2. This article shows that DASSAULT-AVIATION tools allow an accurate prediction of flutter behavior thanks to accounting for all the particular phenomena of T-tail configurations.