High Lift OVERFLOW Analysis of the DLR F11 Wind Tunnel Model

Abstract

In response to the 2 nd AIAA CFD High Lift Prediction Workshop, the DLR-F11 wind tunnel model is analyzed using the Reynolds -averaged Navier-Stokes flow solver OVERFLOW. A series of overset grids for a bracket-off landing configuration is constructed and analyzed as part of a general grid refinement study. This high Reynolds number (15.1 million) analysis is done at multiple angles -of-attack to evaluate grid resolution effects at operational lift levels as well as near stall. A quadratic constitutive relation recently added to OVERFLOW for improved solution accuracy is utilized for side-of-body separation issues at low angles-of-attack and outboard wing separation at stall angles. The outboard wing separation occurs when the slat brackets are added to the landing configuration and is a source of discrepancy between the predictions and experimental data. A detailed flow field analysis is performed at low Reynolds number (1.35 million) after pressure tube bundles are added to the bracket-on medium grid system with the intent of better understanding bracket/bundle wake interaction with the wing's boundary layer. Localized grid refinement behind each slat bracket and pressure tube bundle coupled with a time accurate analysis are exercised in an attempt to improve stall prediction capability. The results are inconclusive and suggest the simulation is missing a key element such as boundary layer transition. The computed lift curve is under-predicted through the linear range and over-predicted near stall, and the solution from the most complete configuration analyzed shows outboard wing separation occurring behind slat bracket 6 where the experiment shows it behind bracket 5. These results are consistent with most other participants of this workshop.

Simulating Aircraft Wake Vortices with OVERFLOW

“…20 This was tested because it was used in a few OVERFLOW studies involving full aircraft. 21,22 The dissipation levels were nearly the same as the SA DES case, the time to dispersion just slightly longer than SA DES but still much less than SST DES and SSTV DES. …”

NASA ERA Integrated CFD for Wind Tunnel Testing of Hybrid Wing-Body Configuration (Invited)

“…In addition, simulations of high-lift configurations on conventional wings often benefit from various forms of "rotation and curvature" (RC) corrections to the turbulence models 16 . The SA-RC model 17 was evaluated in some simulations, and the RC option was also explored within the SST model for some initial simulations.…”

Recent Developments of the Navier Stokes Multi Block (NSMB) CFD solver

“…and applied to the HiLiftPW-2 by Pulliam & Sclafani105 . Lift coefficient (a) and its amplitude (b) versus the angle of attack for several initial conditions.…”