Newton-Krylov algorithm with a loosely coupled turbulence model for aerodynamic flows

A fast Newton–Krylov algorithm is presented that solves the turbulent Navier–Stokes equations on unstructured 2-D grids. The model of Spalart and Allmaras provides the turbulent viscosity and is loosely coupled to the mean-flow equations. It is often assumed that the turbulence model must be fully coupled to obtain the full benefit of an inexact Newton algorithm. We demonstrate that a loosely coupled algorithm is effective and has some advantages, such as reduced storage requirements and smoother transient oscillations. A transonic single-element case converges to 1 1012 in 90 s on recent commodity hardware, whereas the lift coefficient is converged to three figures in one quarter of that time