A NEW VORTEX LATTICE METHOD FOR CALCULATING THE FLOW PAST YACHT SAILS

A new vortex lattice method is described and applied to calculating th e flow past yacht sails. It is based on a reappraisal of conventional approaches to the vortex lattice method and avoids many of their short comings. The new vortex lattice method is regarded as a model of a con tinuous doublet sheet at all times and not simply a set of discrete vo rtices. This interpretation permits the computation of separate pressu res on each side of the surface, rather than just the loading. A speci al choice for the distribution of vortex positions and collocation poi nts on the surface is shown to give very high accuracy with few panels . The method permits vortex shedding from the foot and leach of the sa il and calculates the subsequent roll-up. A recursive sub-panelling an d vortex merging method is used to give stable wake roll-up calculatio ns. Results for an isolated mainsail and an IACC jib/main combination are shown. The results for the IACC rig are compared with those from a Navier-Stokes finite-difference code.