Prediction of separating turbulent boundary layers including regions of reversed flow

Abstract : The results of a research program to develop and evaluate improved prediction methods for turbulent separating flows are summarized. The predictions of several turbulence models have been compared with experimental data for flows containing regions of recirculation using an inverse finite-difference method to solve the boundary layer equations. A new turbulence model which employs a one-dimensional transport equation for the outer-layer length scale was seen to provide the best agreement with the experimental data beyond separation. A viscous-inviscid interaction calculation procedure was developed to predict airfoil flows containing leading edge or midchord separation bubbles. The procedure utilized the inverse finite-difference method to predict the viscous flow and a small disturbance Cauchy integral formulation for the inviscid flow. Three models for laminar-turbulent transition were evaluated. Generally good agreement between predictions of the best model and measurements was observed in the several comparisons made. Some early results from a finite-difference scheme to solve the partially parabolized Navier-Stokes equations in primitive variables were also reported. The method was developed to predict viscous flows in which normal pressure gradients cannot be neglected.