Three-Dimensional Viscous-Inviscid Coupling Using Surface Transpiration

The development of a method to obtain the subsonic flow field about complex, three-dimensional geometries, using the viscous-inviscid iteration technique to correct the potential flow for viscous effects is described. A panel method for the calculation of three-dimensi onal inviscid flow is used iteratively with a two-dimensiona l, integral boundary-layer method. The important feature is the use of surface transpiration to simulate boundary layer effects. The cross flow is neglected in the boundary layer calculations, which are carried out along chordwise strips on the wing. A doubly underrelaxed iteration scheme has resulted in an extremely stable method, which usually gives satisfactory results after 4-5 iterations. The method has been tested on a wide variety of configurations, and the results have been uniformly satisfactory. It has been demonstrated that the method of surface transpiration is completely equivalent to the displacement thickness approach as a means of representing the boundary layer.