Analysis of Unsteady Viscous Flows Past Pitching Airfoils on Unstructured Meshes

A 2-D Navier-Stokes flow solver is developed for the simulation of unsteady, high Reynolds number flows on unstructured meshes. The solver is based on a cell-centered finite-volume method with Roe's flux-difference splitting. In order to relieve the numerical inaccuracy in evaluating the fluxes on hi씽Y-stretched, high-aspect ratio triangular cells, a hybrid mesh is used. The Spalart-Allmaras and turbulence models are employed in order to model the effect of the fluid turbulence in the mean flow equations. The governing equations and the turbulence model are integrated in time using an implicit time-marching method. The point Gauss-Seidel relaxation and a dual-time stepping method have been incorporated. The numerical method is applied to a low angle-of-attack oscillatory airfoil motion and ramp motions. The results are compared with experimental data for validations.