Verification of the γ-Reθt Transition Model in OVERFLOW and FUN3D

Abstract

The findings of the recent AIAA and NATO workshops on transition modeling have underscored the importance of verifying the transition models that are based on Reynolds-averaged Navier–Stokes. To that end, the present work aims to verify the Langtry–Menter (LM2009) transition model coupled with Menter’s shear-stress transport (SST) turbulence model. Specifically, the SST-2003-LM2009 model, as implemented in the OVERFLOW structured overset solver and the FUN3D unstructured solver, is applied to both natural and bypass transition scenarios on a flat plate and to natural and separation-bubble-induced transition on the NLF-0416 airfoil. The Richardson extrapolation method was used to analyze and report the grid convergence of integrated and local load coefficients upstream, within, and downstream of the transition region, based on solutions obtained using the two solvers on identical grids. Reasonable agreement is obtained between the two codes for both global and local surface load coefficients when further refining the workshop mesh series, although with a grid-convergence index for the local friction coefficient that may exceed 1% in certain cases. The study also highlights the solution sensitivity to the choice of turbulence inflow boundary conditions and model options, along with the necessity to unambiguously specify this information for benchmark exercises.