Application of the vortex-lattice concept to flows with smooth-surface separation

Numerical schemes based on the vortex-lattice concept have had considerable success in treating the fully three-dimensional separated potential flow over low aspect-ratio thin wings at high incidence and the attached potential flow over bodies of more general shape. In principle, the vortex-lattice method is not limited in application as long as convection dominates vorticity diffusion. A non-linear 3-D vortex-lattice method was developed which treats the steady separated flow over prolate bodies with open separation moving through an inviscid incompressible fluid. The strength and position of the body wake were found as part of the solution. Flows with smooth-surface separation were considered as opposed to flows with sharp-edge separation treated with the vortex-lattice concept in the past. Results for flow over an inclined ogive-cylinder demonstrated the technique. For attached flow, comparisons are presented of the results from the vortex-lattice method using optimal and average control point locations with the results of the source-distribution method and with experimental data. The same panel arrangement was used calculating both methods. The results of the present method are somewhat more sensitive to panel arrangement than are those for the source-distribution method. Also, the effect of control point location varies dramatically as the incidence of the body is changed. For separated flow, results of the vortex-lattice method were compared with experimental data and with the results of a typical 2-D analogy. The present method agrees favorably with the experimental data windward of a separation line.