Performance of wall-modeled LES for external aerodynamics in the NASA Juncture Flow

Abstract

The use of computational fluid dynamics (CFD) for external aerodynamic applications has been a key tool for aircraft design in the modern aerospace industry. CFD methodologies with increasing functionality and performance have greatly improved our understanding and predictive capabilities of complex flows. These improvements suggest that Certification by Analysis (CbA) -prediction of the aerodynamic quantities of interest by numerical simulations (Clark et al. 2020) may soon be a reality. CbA is expected to narrow the number of wind tunnel experiments, reducing both the turnover time and cost of the design cycle. However, flow predictions from the state-of-the-art CFD solvers are still unable to comply with the stringent accuracy requirements and computational efficiency demanded by the industry. These limitations are imposed, largely, by the defiant ubiquity of turbulence. In the present work, we investigate the performance of wall-modeled large-eddy simulation (WMLES) to predict the mean flow quantities over the fuselage and wing-body junction of the NASA Juncture Flow Experiment (Rumsey et al. 2019).Computations submitted to previous AIAA Drag Prediction Workshops (Vassberg et al. 2008) have displayed large variations in the prediction of separation, skin friction, and pressure in the corner-flow region near the wing trailing edge. To improve the performance of CFD, NASA has developed a validation experiment for a generic full-span wing-fuselage junction model at subsonic conditions. The reader is referred to Rumsey et al. (2019) for a summary of the history and goals of the NASA Juncture Flow Experiment (see also Rumsey & Morrison 2016;. The geometry and flow conditions are designed to yield flow separation in the trailing edge corner of the wing, with recirculation bubbles varying in size with the angle of attack (AoA). The model is a full-span wing-fuselage body that was configured with truncated DLR-F6 wings, both with and without leading-edge horn at the wing root. The model has been tested at a chord Reynolds number of 2.4 million, and AoA ranging from -10 degrees to +10 degrees in the Langley 14-by 22-foot Subsonic Tunnel. An overview of the experimental measurements can be found in Kegerise et al. (2019). The main aspects of the planning and execution of the project are discussed by Rumsey (2018), along with details about the CFD and experimental teams.To date, most CFD efforts on the NASA Juncture Flow Experiment have been conducted using RANS or hybrid-RANS solvers. Lee et al. (2017) performed the first CFD analysis to aid the NASA Juncture Flow committee in selecting the wing configuration for the final experiment. Lee et al. (2018) presented a preliminary CFD study of the near wing-body juncture region to evaluate the best practices in simulating wind tunnel effects. Rumsey et al. (2019) used FUN3D to investigate the ability of RANS-based CFD

Non-Boussinesq subgrid-scale model with dynamic tensorial coefficients

“…Previously, comparisons between surface streamlines of skin friction from the LES have been compared with experimental visualizations to qualitatively study the nature of the flow structures [20,22,34]. For this flow, Williams et al [55] performed clay-kerosene mixture based visualizations and observed a pair of counter-rotating vortices in the aft section of the bump.…”