Improved Iteration Algorithm for Nonlinear Vortex Lattice Method

Abstract

VORTEX lattice method (VLM) based on inviscid theory is widely used in practice as it is very effective for aerodynamic design. As conventional VLM is not suitable for aerodynamic analysis of low-aspect-ratio wings or wings at a high angle of attack, nonlinear VLM (NLVLM) was introduced in the 1970s [1–3]. Since then, NLVLMhas been adopted frequently for aerodynamic analysis of low-aspect-ratio wings, delta wings, slender bodies, etc. (as can be found in [4–12]). In NLVLM, vortex segments of a free vortex of a horseshoe vortex system are allowed to move to be aligned with local streamlines, and this inevitably requires an iterative numerical procedure. Convergence property of the iteration algorithm employed in the calculation is therefore a very practical concern [6,8,9]. In this work, we propose a modified iteration algorithm, which has been found to be more efficient and stable than the conventional method often adopted for NLVLM.