A systematic investigation of the parameters affecting the accuracy of the vortex-lattice method

A procedure is developed to examine the parameters affecting the accuracy of the vortex-lattice method when applied to a nonlinear lifting surface problem with leading edge separation. Among the factors investigated are the extensions of the bound vortex segments off the sharp edges of the wing, modifications of the Biot-Savart law to damp out near singularities, the length of the free vortex segments, the placement of the control points on the surface of the wing, and methods of applying the no-penetration boundary condition and spatial conservation of circulation. Two methods of force and pressure calculations are considered and an interpolation procedure is introduced to represent the pressure distribution as a continuous function over the surface of the wing. Delta, arrowhead, and cropped delta wings are presented as numerical examples. Parametric studies are made for the delta wing of aspect ratio one. It is found that the parameter which has the greatest influence on the solution is the extension of the bound vortex segments adjoining the leading edge off the leading edge.