Finite element computation of turbulent flow past a multi-element airfoil

Abstract

Flow past multi-element airfoil is studied via two-dimensional numerical simulations. The incompressible Reynolds averaged Navier-Stokes equations, in primitive variables, are solved using a stabilized finite element formulation. The Spalart-Allmaras and Baldwin-Lomax models are employed for turbulence closure. The implementation of the Spalart-Allmaras model is verified by computing flow over a flat plate with a specified trip location. Good agreement is seen between the results obtained with the two models for flow past a NACA 0012 airfoil at 5° angle of attack. Results for the multi-element airfoil, with the two turbulence models, are compared with experiments for various angles of attack. In general, the pressure distribution, from both the models matches quite well with the experimental results. However, at larger angles of attack, the computational results overpredict the suction peak on the slat. The velocity profiles from the Baldwin-Lomax model are, in general, more diffused compared to those from the Spalart-Allmaras model. The agreement between the computed and experimental results is not too good in the flap region for large angles of attack. Both the models are unable to predict the stall; the flow remains attached even for relatively large angles of attack. Consequently, the lift coefficient is over predicted at large α by the computations. Overall, compared to the Baldwin-Lomax model, the predictions from the Spalart-Allmaras model are closer to experimental measurements.