Implementation and Investigation of a Local Correlation-based Transition Model in a Parallel Newton-Krylov-Schur Algorithm

Aircraft with significant regions of natural laminar flow provide the opportunity for reduced fuel consumption. However, many conventional computational fluid dynamics algorithms assume that the flow is fully turbulent, which limits the development of natural-laminar-flow designs. A three-dimensional Reynolds-averaged Navier-Stokes flow solver has been expanded to include the prediction of laminar-turbulent transition. This was achieved by coupling the Spalart-Allmaras turbulence model with the γ - Reθt local empirical correlation-based transition model. The stability and robustness of the solution algorithm was optimized in order to obtain efficient and reliable convergence. The performance of the algorithm was investigated through application to several two-dimensional verification and validation cases, including flat-plate test cases, natural-laminar-flow airfoils, and a multi-element high-lift airfoil configuration. The results demonstrate the ability of the model to predict locations of transition in complex flow regimes which match experimental results for cases involving natural and separation-induced transition.M.A.S