Computation of Trailing-Edge Separation Using an Accelerated, Updated Bluff-Body, Interacting Boundary-Layer Algorithm

Abstract

An interacting boundary algorithm is developed to efficiently solve for high Reynolds number flow past realistic airfoil geometries. The algorithm is fully asymmetric, although only symmetric profiles are addressed in this study (primarily the NACA00xx series). The interacting boundary layer algorithm is based on a bluff-body formulation that linearizes the thin airfoil integrals about some known exact inviscid baseline solution. The present formulation solves for the baseline inviscid flow using Theodorsen’s method and allows updating of the baseline solution. An acceleration scheme is developed which allows an extrapolation to the final converged solution from information obtained early in the iteration cycle. It is found that separation bubbles of up to 35% of chord in length can be accurately calculated on fine grids in under 40 global iterations. Furthermore, both the updating of the baseline coordinate curve and the FLARE approximation are found to have a large impact on the solution — arguing against the accuracy of thin-airfoil based interacting boundary layer models for separation bubbles above 5% of chord in length. Comparisons are made with interacting boundary layer and full Navier-Stokes computations.