Computational and Experimental Comparison of a Powered Lift, Upper Surface Blowing Configuration

Abstract

This paper demonstrates the use of CFD as a validation tool for wind tunnel data on 2D high lift airfoil with a 3D engine performed by Georgia Tech Research Institute. Results of this validation will assist in determining the appropriate turbulence models, boundary conditions, mesh characteristics and other CFD modeling techniques necessary to capture the complicated flow physics associated with the coupling of circulation control wings and engine exhaust flows. It was found that grid issues and the two-equation turbulence model, k-ε, over predicted lift as blowing momentum increases even with the additional complexity of having an over the wing engine. The detailed techniques utilized to most accurately capture the flow properties, including lift forces and flow field characteristics, are provided and discussed.

Design and Performance of Circulation Control Geometries

“…The realizable k-ε turbulence model was chosen over the one-equation Spalart-Allmaras 57,61,94 and two-equation k-ω 95 models because of its ability to capture features of turbulence with a high quality near-wall mesh, 55 and being commonly used and robust. 51 Although one-and two-equation turbulence models have been shown to typically overpredict the lift coefficients of airfoils in CC flows, 50,[52][53][54][55][56][57][58][59]61,80,81,83 the chosen model has shown benefits over other models in parametric studies and has been proven to consistently depict aerodynamic trends of CC flow features. 96 The over-prediction of lift is caused by over-predicting turbulent kinetic energy 56…”

“…By selecting a value well within the super-circulation regime, it ensured that each configuration would not experience jet separation prior to the end of the flap surface leading to a non-biased performance evaluation. Jet separation on the radial surfaces of a CC flap has also been shown to be difficult to predict using CFD [56][57][58][59][81][82][83]. Flap Placement/IntegrationTo place the flap on the airfoil(Figure 3-6a.…”