An Improved Smooth Rotation Correction for the Spalart–Allmaras Turbulence Model for Better Off-Body Vortex Prediction and Vortex–Vortex Interaction Effects

This work presents a new modification of the Spalart–Allmaras (SA) turbulence model, named SA-R23, to improve the capture of off-body vortices in the flow by means of a smooth Rotation correction. The new rotation correction has the same basics as the one of Dacles-Mariani et al. (SA-R) (Dacles-Mariani et al. 1995. “Numerical/experimental Study of a Wingtip Vortex in the near Field.” AIAA Journal 33 (9): 1561–1568), but has more favourable numerical properties especially for high-order Navier–Stokes solvers. The key mission of the -R models is to prevent the intense dissipation of the cores free vortices by the Spalart–Allmaras model; other eddy-viscosity models have similar issues. This makes Delta and similar wing configurations excellent cases for validation, which is facilitated by recent three-dimensional experimental measurement systems. The tightened vortices also have a favourable impact on commercial-airplane high-lift systems, helicopter and open-rotor blade-vortex interactions, vortex generators, cavitation and contrails. This paper also shows the ability of metric-based anisotropic mesh adaptation combined with the -R models to accurately capture complex off-body flow physics. The approach is challenged on a particularly complex test case: a generic military aircraft with varying leading-edge sweep at high angle of attack. Detailed flow-field comparisons are shown, as well as the mesh convergence of aero coefficients and force polars.