Interference Drag Modeling and Experiments for a High-Reynolds-Number Transonic Wing

Multidisciplinary Design Optimization (MDO) studies show the Strut/Truss Braced Wing (SBW/TBW) concept has the potential to save a significant amount of fuel over conventional designs. For the SBW/TBW concept to achieve these reductions, the interference drag at the wing strut juncture must be small compared to other drag sources. Computational Fluid Dynamics (CFD) studies have indicated that the interference drag is small enough to be manageable. However, the RANS formulation and turbulence models used in these studies have not been validated for high Reynolds number transonic junction flows. This study assesses turbulence models by comparing flow separation characteristics obtained from experiment and CFD. The test model used is a NACA 0012 wing of aspect ratio 2 at Mach number of 0.76 and a Reynolds number of 6 million with varying angle of attack. The CFD study involved an 18.8 million cell structured grid of the wind tunnel test section using the ANSYS Fluent 12.0 solver. The k-ω SST turbulence model was the main turbulence model employed. Experiments were conducted in a high Reynolds number transonic Ludwieg tunnel. The wing was tested at different Mach numbers and inlet conditions to account for some of the experimental variations. Porous walls eliminate shock reflection across the tunnel. Surface oil flow visualization is used to indicate the interference flow patterns. The assessment shows CFD overpredicts separation and therefore interference drag, likely due to deficiencies in the turbulence model. Nomenclature