3D RANS Simulations for Transport Aircraft High Lift Configurations

Abstract

Computations of lift and drag polars for a transport aircraft wing/fuselage high lift configuration using the MEGAFLOW code system are carried out and compared to windtunnel experiments. The main emphasis is laid on a comparison of the block-structured and the unstructured code modules for such type of application. For the block-structured FLOWer code in combination with a k-w turbulence model the numerical results are in good agreement with the available experimental data in the linear CL range. Beyond 150 incidence a strong separation near the flap cut-out is simulated, leading to an underprediction of total lift near CL, max compared to the experimental data. In contrast to this, the results ofthe unstructured TAU code utilizing the Spalart-Allmaras turbulence model are characterized by a nearly constant lift overestimation up to maximum lift without the aforementioned separation tendency at moderate incidences. The lift overprediction in the unstructured results is attributed to the main wing and the slat upperside suction peaks, which are higher resolved by the unstructured grid. Neither code reproduces the lift breakdown beyond CL, max according to the experiments. The use of preconditioning in conjunction with the FLOWer code shows only minor improvement of the accuracy, but considerable deterioration of the convergence properties, requiring improvements for routine use. Further studies will focus on the influence of geometry simplifications at the wing root in the theoretical models and its impact on the experimental evidence.