A Vortex-Lattice Method for the Calculation of Wing-Vortex Interaction in Subsonic Flow

Summary

Flow interferences between wings and free vortex sheets (e.g. canard-wing with vortex separation) can influence the aerodynamic characteristics of a configuration to a considerable extent. If viscous and turbulent effects are negligible, potential flow methods represent a suitable way to calculate wing-vortex interactions and in many cases lead to simpler mathematical structures than Euler methods.

The present vortex lattice method [1] is based on a time-dependent, discrete procedure with zero order doublet distributions. Except of the kinematic flow condition at the wing, all other boundary conditions are implicitely fulfilled by the mathematical model itself. Subsequently, iterations or the prescription of a starting solution is not necessary. At the shear layers, a continuous velocity distribution is indispensable for a successful analysis of interference effects. This problem, which all low order panel methods have to face, compare [2], is solved by spline functions and a differencing scheme.

The method is designed for subsonic flow and single or coupled plane, thin wings with or without vortex separation at the sharp wing edges. Potential flow effects (e.g. primary vortex) and their influence on the wing loads and the velocity field are reproduced in good agreement with experiments. In some cases, hints on a beginning vortex break down are possible. Variations of the free stream U→_∞, (t) can be simulated, low Strouhal numbers presumed.

With these attributes, the vortex lattice method offers a reliable and versatile concept to gain insight in basic wing-vortex interactions at low computational effort.