· · · Aerospace Engineering reports

For the limiting cases of conical flow about delta wings and time dependent 2-D development of the wake behind the trailing edge of wings a new second-order panel method is described. It is demonstrated that the panel method is stable for the mixed design/analysis boundary conditions characterizing both problems. The method for following 2-D vortex sheet motion includes an adaptive curvature-dependent panel scheme and a concept for doubly-branched spiralling vortices, which enables the motion of vortex sheets of complicated shape to be followed up to large downstream distances. Conical flow results are presented for different angles of attack and for different cross-sectional shapes. Vortex sheet roll-up results are presented for the wake behind a flat delta wing.

The paper describes a computational method for two-dimensional vortex sheet motion in incompressible flow. The procedure utilizes a second-order panel method, an adaptive panel scheme and a concept for treating highly rolled-up portions of the vortex sheet. Results are presented for the roll-up of the wake behind an elliptically loaded wing, a ring wing (nacelle), a fuselage/Part-span-flap/wing combination and a delta wing with leading-edge vortex sheets. The examples demonstrate that the method is capable to describe complicated vortex sheet motion in a reliable and stable manner.

An experimental and theoretical investigation is described of the flow above and downstream of a 76° delta wing and two double-delta wings (sweep 76°/60° and 76°/40°, respectively, kink at 50 % chord). The flow pattern is visualized employing a laser-light-sheet technique. For the case of the delta wing experimental results are compared with numerical results of a free-vortex sheet method for computing three-dimensional flow about slender wings, a free-vortex sheet method for the limiting case of conical flow and a computational procedure for computing two-dimensional time-dependent vortex wake roll-up. Based on the laser-light-sheet investigation a vortex-sheet model is proposed for the flow about double-delta wings with leading-edge vortex separation on both wing panels. Presented as AIAA Paper 82-0949 at the AIAA/ASME 3rd Joint Thermophysics, Fluids, Plasma and Heat Transfer Conference, June 7-11 1982, St. Louis, Missouri, USA.