Comparison of Flow-Solvers: Linear Vortex Lattice Method and Higher-Order Panel Method with Analytical and Wind Tunnel Data

Abstract

Two induced drag analysis techniques, Vortex Lattice Method (VLM) and panel method are renowned for inviscid aerodynamic computations and are widely used in the aerospace industry and academia. To demonstrate the applicability of potential flow theory and to establish an extensive correlation of linearized, attached potential flow-solver codes for estimating lift and induced drag, a generic rectangular wing planform is analyzed. Due to a wide range of applicability in conceptual design, the two solvers are compared for accuracy, computational time and input controllability to find an optimum solver that can predict inviscid aerodynamics accurately and efficiently but with the least amount of time. VLM-based code is founded upon the Laplace equation. It approximates a three-dimensional wing into a two-dimensional planform, making it apposite for moderate aspect ratio and thin-airfoil aircraft. A modified VLM is used that takes a suction parameter, calculated analytically, as an input to capture three-dimensional leading-edge thrust and vortex lift effects. On the contrary, the higher-order panel method takes the complete wing surface and changes the wake orientation to model modified flow to better predict the effects of downwash. These codes, allow computation in both subsonic and supersonic regimes, as they include Prandtl-Glauert compressibility correction. The rectangular wing is generated with an identical number of panels and networks for coherent comparison. Distinguishable pre-processing techniques are utilized and similar boundary conditions and flow conditions are maintained over the surfaces that are then given to solvers. The induced drag polar is plotted and compared with wind tunnel and analytical data.