Application of a Vortex Lattice Method Solver to an Aircraft Sizing Framework

Abstract

A Vortex Lattice Method (VLM) solver is developed to estimate the aerodynamic performance of lifting surfaces, while operating within the assumptions of Potential Flow. The VLM solution is found by representing an aircraft configuration's lifting surfaces using a mesh of bound vortices and wake segments enabling the computation of the aerodynamic forces and moments acting on the vehicle. Applying this method, the influence of each panel on every other panel is computed. This process inherently incorporates the influence of each lifting surface on every other lifting surface. To extend the applicability of the method beyond incompressible flow, compressibility corrections were applied.

Before the solver was incorporated into an aircraft sizing framework for the evaluation of forces and moments produced by lifting surfaces while in flight, validation studies were completed. Validation of the VLM solver was performed by initially comparing the output with experimental data to verify the spanwise loading and overall lift prediction were accurate. Next, the VLM model was compared with other state-of-the-art Potential Flow solvers, and it was concluded that the model was producing data with a satisfactory level of accuracy.

The VLM solver was then implemented into the Parametric Energy-based Aircraft Configuration Evaluator (PEACE) aircraft sizing framework to combine the VLM solution with fuselage and two-dimensional airfoil data to determine the full aircraft forces and moments. When the fuselage data was combined with the VLM solution, the method produced precise results for low angles of attack. As predicted from the formulation of the Vortex Lattice Method, the solution began to diverge from viscous solutions as the angle of attack increased.