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Aircraft configurations with deployed control surfaces are increasingly in the limelight of aerodynamic investigations using high-fidelity based Computational Fluid Dynamics to possibly reduce the conservatism in the design process. So far, most applications focus on static control surface deflections. To close the gap towards future simulations of entire flight maneuvers, including gust encounters, the dynamic motion of the control surfaces and their transient impact on the aircraft configuration need to be taken into account. Hence, extending the application range of its flow solver TAU is of strategic interest for the Institute of Aerodynamics and Flow Technology of the German Aerospace Center (DLR). To support these numerical activities DLR developed a wind tunnel model with an active spoiler. In collaboration with German-Dutch Wind Tunnels, the aerodynamic performance of this model has been examined in two wind tunnel campaigns in 2016, focusing on static and dynamic spoiler deflections. The present paper gives an overview on the motivation of this work and highlights the experimental setup as well as exemplary results. The data will later be used to further validate the DLR flow solver TAU.

A summary about the DLR, German Aerospace Center results from the fourth AIAA Computational Fluid Dynamics Drag Prediction Workshop is presented. Compared to the investigations in the previous three workshops, the latest workshop had a stronger focus on drag and trim drag predictions as well as pitching moment calculations. Therefore, the new Common Research Model developed by NASA's Subsonic Fixed Wing Aerodynamics Technical Working Group and tested in NASA wind tunnels is used. It represents a state-of-the-art transonic transport aircraft configuration, and in contrast to the configurations previously taken, it includes an optional horizontal tailplane with three different tail settings. DLR has defined three objectives for its activities in the fourth drag prediction workshop. At first, investigations should identify solution accuracy and grid convergence behavior using prismatic element dominant grids for boundary-layer resolution in comparison to hexahedral element dominant grids. Second, the influence of turbulence models of increasing complexity is of interest regarding transonic pressure distributions and flow separations. Therefore, the one-equation turbulence model of Spalart and Allmaras, the two-equation Menter kω-shear-Stress-transport model, and the Speziale-Sarkar-Gatski/Launder-Reece-Rodi-ω Reynolds-stress model are applied. The third objective is to analyze what differences in the calculated pitching moments and horizontal tailplane trim angles can be expected for the Common Research Model with different horizontal tailplane settings when grids are regenerated for each setting or when they are deformed iteratively based on the grid for the initial setting. All investigations are performed with the grid generation software Solar and Centaur™ and the Reynoldsaveraged Navier-Stokes solver TAU. Recently, selected experimental data have been released by NASA and are used here for comparisons.

A numerical study was carried out to assess the interference effects between the wake of a transport aircraft and several generic cargo bodies during the early stage of an airdrop scenario. DLR carried out extensive wind tunnel airdrop investigations between 2006 and 2012. Based on the experimental data and preceding numerical simulations distinct positions of the trajectory being subject to strong interference effects were statically reproduced. The flow field around the bodies was experimentally investigated using stereoscopic Particle Image Velocimetry and compared to steady and unsteady Reynoldsaveraged Navier-Stokes (RANS) computations. The latter were carried out using the unstructured DLR TAU code. The primary focus is to assess the suitability, accuracy and the limitations of RANS methods in such challenging flow conditions. Therefore, the influence of several turbulence models was investigated and compared to experimental field velocity data. In addition, an exemplary unsteady RANS simulation was conducted to highlight the differences to the steady approach. Although deviations in the wake of the bodies were observed, the qualitative agreement between the steady simulations and experiment was very good. Quantitatively, however, the steady approach leaves room for further improvements. The gap to the experimental data could partially be reduced in applying unsteady RANS methods.

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