Wind tunnel flutter test results comparison with computational results of a half-span wing

Kurzfassung

A half-span wing was designed for wind tunnel test for verification of aeroelastic characteristics in 2017. This wing was quite flexible and fitted with a pylon and a flow thru nacelle, to represent the geometry and mass distribution of real-life aircraft, but without propulsion effects. The wind tunnel used in 2017 for aeroelastic tests was the DNW-HST in Amsterdam, The Netherlands. The test was split in two parts: the first campaign focused on wing deflection for each test point and on how the flexibility affected the flutter characteristics. The second part was dedicated to higher Mach numbers and low angles of attack to verify the effect of both flexibility and shock waves on the aeroelastic characteristics of the system. The wind tunnel test instrumentation included steady and unsteady pressure taps, accelerometers, strain gauges, stereo pattern recognition, and others. All wind tunnel measurements were in good agreement to the computational results, obtained by using traditional tools, such as Nastran. However, for the second entry, considering Mach numbers from 0.75 to 0.90, the behaviour of both damping and frequency are slightly different from the computational analysis, especially for the first five aeroelastic modes. The results were obtained for three different configurations by varying the wing tip mass. Since there are some differences between the experimental and computational results for the transonic regime, further analysis is performed to explore the effects of aerodynamic nonlinearities. To investigate it in more detail, analyses using different computational tools for the transonic unsteady aerodynamics from Embraer and DLR is used in the present paper and compared with the experimental results obtained in 2017. The focus is to use high fidelity methodologies based on coupled CFD/CSM-methods (computational fluid dynamics, computational structure mechanics) for the flexible model to better capture nonlinear phenomena that might be occurring during the wind tunnel tests.