The effects of the wing skin distortion on the boundary layer of a highly flexible wing are analyzed in a wind tunnel experiment using infrared thermography measurements. Considerable differences in the boundary layer flow are observed when comparing the sections of the wing near the ribs, where the design shape of the wing is preserved, and in between the ribs. At the spanwise locations between the ribs, the sectional wing shape distorts and triggers boundary layer transition close to the leading edge. The differences between the design behavior of the wing and the experimental results of the boundary layer analysis demonstrate the need for considering the skin deformation and its effects on the boundary layer flow when designing highly flexible wings.

@en

The Pazy Wing test case is a benchmark for the investigation of aeroelastic effects at very large deflections. Tip deformations in the order of 50% span were measured in wind tunnel tests which renders this model highly attractive for the validation of numerical aeroelastic methods and tools for geometrically nonlinear, large deflection analyses. The present work is focused on high fidelity aerodynamic and aeroelastic simulations of the wing using RAN and URANS with transition modeling in order to capture nonlinear effects originating from the shape of the wing and the low Reynolds number. Steady and unsteady aerodynamic as well as static coupling simulations with a nonlinear structural model are presented, the impact of the different transition and turbulence modeling techniques is depicted. This work supports the Large Deflection Working Group (LDWG), which is one of the sub-groups of the 3rd Aeroelastic Prediction Workshop (AePW3). The work of NASA to generate a highly accurate geometry file for the generation of the CFD grid based on the scanned outer surface of the TU Delft Pazy Wing is gratefully acknowledged. Furthermore, the help of the members of the Large Deflection Working Group of the AePW3 is appreciated, especially for the setup of the beam model (Cristina Riso and Bret Stanford) as well as the experimental data (Arik Drachinsky and Daniella Raveh). Also the support of the DLR Institute of Aeroelasticity for this work is acknowledged.

@en

The Pazy Wing test case is a benchmark for the investigation of aeroelastic effects at very large deflections. Tip deformations in the order of 50% span were measured in wind tunnel tests, which renders this model highly attractive for the validation of numerical aeroelastic methods and tools for geometrically nonlinear, large deflection analyses. Due to the low flow velocity (up to 60 m/s) and the simple geometry of the wing, simulation programs based on subsonic, linear potential aerodynamic solvers (such as VLM and UVLM) are an ideal basis for static coupling and flutter simulations. However, more comprehensive analyses with focus on aerodynamic nonlinearities such as stall and limit cycle oscillations (which have been observed in several wind tunnel tests) are attractive research topics but call for advanced aerodynamic methods. The present work is thus focused on high fidelity aerodynamic simulations of the Pazy Wing using RANS with transition modeling in order to capture nonlinear effects originating from the particular shape of the wing and the low Reynolds number. It is a collaborative activity of DLR, NASA, and TU Delft and supports the Large Deflection Working Group (LDWG), which is one of the sub-groups of the 3rd Aeroelastic Prediction Workshop (AePW3).@en