Three dimensional flow analysis by the vortex-lattice method

A Vortex-Lattice Method (VLM) has been developed for the analysis of three-dimensional lifting bodies undergoing arbitrary motions. So far, the present method has been applied to thin surfaces in translational motion. Several cases were tested, such as rectangular, delta, sweptback and trapezoidal planforms. Emphasis has been placed on the comparison of the results with available experimental data. Consequently, many of the strengths and limitations of the technique were made apparent. Good agreement has been obtained for the aerodynamic coefficients, with a relatively coarse discretization of the surface. Results are valid as long as there is no separation or vortex breakdown. However, accurate pressure distribution calculations need at least three or four times the number of panels used for aerodynamic coefficients calculations. The method gives a qualitative description of the wake configuration, but unrealistically high velocities are induced near the vortex elements. Work is underway to extend the technique to more general types of bodies and maneuvers.