Roll up of strake leading/trailing-edge vortex sheets for double-delta wings

Abstract

ConclusionsThe Infuence Function Method previously has been demonstrated to be a revolutionary new tool for the prediction of store loads in aircraft flowfields. The major limitation of the method-the difficulty and expense involved in the calibration process-has been addressed for standard missile configurations by coupling the IFM with the Interference Distributed Loads code. Significant cost reductions have been realized with no compromise in the accuracy of the IFM predictions. an Aircraft," AIAA Paper 83-0266, Jan. 1983.tices and the complex naturfe of vortex sheets of double-delta wings (according to Hummers experiments, three concentrated vortices are probably formed), the author will not employ any artificial smoothing scheme. The main purpose of this Note is to examine the capability of a simple, twodimensional point vortex method to simulate roll up of complicated strake leading/trailing-edge vortex sheets rather than to investigate smoothing schemes. Further, the effect of the interaction of those vortex sheets on the downwash field will be considered. Theoretical ModelThis model is similar to the one used by Sacks et al. 5 According to the slender wing assumption, the original threedimensional steady flow around a wing can be analyzed approximately by a two-dimensional time-dependent flow analogy. The separated free shear layer emanating from the leading edge of the wing is replaced by a finite number of twodimensional point vortices. Each point vortex represents the vorticity shed from the leading edge during a time interval. Sacks' model does not rely on the assumption of conical flow.It is convenient to use complex variables. In terms of conformal mapping, the wing section in the physical plane, X-y^-iz, is mapped onto a circle in the transformed plane, f=£ + /r7, and the resulting problem is reduced to the flow around the circle with a finite number of point vortices outside the circle. For flat-plate wing the transformation is the Joukowski transformation, X= [f+ (a 2 /$) ], where a is the radius of the circle. Therefore, the complex velocity potential,