Résumé
The ongoing development of low order methods providing fast estimations of aerodynamic loading are essential for pre-dimensioning and optimization of wings and fins. The aim of this study is to present an efficient 3D Non-Linear Lifting-Line Method enhanced by an artificial viscosity correction, able to give reliable results for post-stall regime, where conventional lifting-line methods usually fail. In the present method, the lifting-line governing equation is solved by a Newton-Raphson algorithm, with an analytical Jacobian matrix. An artificial viscosity term has been added to the governing equation, in order to regularize the solution for post-stall regime. A unique parameter was defined to control the amount of artificial viscosity introduced in the governing equation. The investigations focus on the influence of the amount of artificial viscosity on the regularization of the final solution. The perturbation generated by the artificial viscosity on the governing equation is also analyzed. The method has been validated and evaluated with linear and non-linear test cases, from analytical and experimental data from the literature. It was shown that there is an optimal amount of artificial viscosity leading to a converged solution, for post-stall regime, associated with smooth circulations along the wing span, coherent 3D lift coefficients, and low deviations from the initial governing equation. When the amount of artificial viscosity increases beyond this optimal value, the solution deteriorates. The optimal value of the parameter controlling the amount of artificial viscosity has been found to be practically insensitive to the angle of attack, and to the wing discretization.