The use of the nonlinear, steady vortex-lattice technique to treat close-coupled sails is described. The sails are modeled as highly cambered, twisted lifting surfaces. The aspect ratio and planform can be arbitrary. The technique is limited by the angle of attack as long as separation occurs along the leech only. Due to the aerodynamic interference of the various sails, the wakes adjoining the leeches are an important feature of the flow. Here we obtain the vortex strength in, and the shape of, the various wakes as part of the solution. Moreover, the vortex lines representing the sails lie on the surface of the sail; they are not projected onto a plane surface. Numerical results for an arbitrarily chosen ketch rig are given. These results include the shapes of the wakes and a typical chordwise pressure distribution.
A Computer-Based Method for Analyzing the Flow Over Sails
Thrasher, D. F., Mook, D. T., and A. H. Nayfeh. "A Computer-Based Method for Analyzing the Flow Over Sails." Paper presented at the SNAME 4th Chesapeake Sailing Yacht Symposium, Annapolis, Maryland, USA, January 1979. doi: https://doi.org/10.5957/CSYS-1979-009
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