Free-Air Simulation Sensitivities on NASA’s High-Lift Common Research Model

Abstract

To reduce the time-to-market of future aircraft, it is crucial to predict the flight envelope accurately before building prototypes for flight tests. The High-Lift Prediction Workshop series aims to assess the numerical prediction capability of current computational fluid dynamics technology considering the high-lift version of the NASA’s Common Research Model. The present work contributes to these collaborative efforts, quantifying sensitivities for Reynolds-averaged Navier–Stokes (RANS)–based steady, unsteady, and hybrid RANS/large-eddy-simulation scale-resolving approaches. Uncertainties associated with the choice of turbulence model, initialization strategies, grid resolution, and iterative convergence at free-air conditions are covered. Near stall, a large spread of RANS results was observed for different turbulence models and initialization strategies, while iterative convergence appeared less crucial for the present simulations. Steady and unsteady RANS simulations were unable to predict the correct flow physics near [Formula: see text], even for large grids. Delayed detached-eddy simulations (DDES), however, showed good accuracy compared with wind-tunnel experiments and predicted [Formula: see text] with an error of around 5%. Compared to steady RANS, the computational cost of DDES was a factor of 10 higher. Lessons learned and potential best-practice strategies are shared to aid future studies. While warm-started RANS simulations using Spalart–Allmaras models are recommended at lower angles of attack, scale-resolving methods are required near stall.