RANS Simulation and Experiments on the Stall Behaviour of an Airfoil with Laminar Separation Bubbles

Abstract

Measurements and simulations are presented of the flow past a tailplane research airfoil which is designed to show a mixed leading-edge trailing-edge stall behaviour. The numerical simulations were carried out with two flow solvers that introduce transition prediction based on linear stability theory to RANS simulations for cases involving laminar separation bubbles. One of the methods computes transition locations across laminar separation bubbles whereas the other assumes transition onset where laminar separations occur. For validation of the numerical methods an extensive measurement campaign has been carried out. It is shown, that the methodology mentioned first can simulate the size of laminar separation bubbles for angles of attack up to where the separation bubble and the turbulent separation at the trailing edge are well behaved and steady in the mean. With trailing edge separation involved, the success of the new numerical procedure relies on the diligent choice of a turbulence model. Cases with large 3D flow structures inside the turbulent trailing edge separations in windtunnel experiments for high angles of attack are compared and analysed along with 2D and 3D steady RANS calculations that model the measurement section of the windtunnel.