I am looking at modelling sails and having done some research it seems most of industry use vortex methods of some sort. Is it not correct that they cannot model seperation well which would make them not accurate for sails. Why are Rans models not used more widely? Also anyone know any specific software used for sail flows?

I guess the problem with sails lies not so much in the choice of flow equations but in the choice of computational methods, in particular grid based versus gridless methods. If you allow your sail to be highly convoluted (flutter), it will be difficult or inefficient to apply a grid based flow model. Maybe it is for this reason that certain gridless methods (e.g. vortex methods) are preferred.

more than likely in the flow regime that most sailboats operate in, effects like flow separation will be secondary compared to the effect of self-induced oscillations(ie flutter). The flutter boundary will be modeled more than accurately using vortex methods and only if you plan on looking at nonlinear phenomena such as LCO will you need to consider nonlinear effects such as geometric nonlinearity(structural) and flow separation(fluid).

Jon, I know nothing about analyzing them, only adjusting while racing. However, take a look at this site, you may find it interesting: http://syr.stanford.edu/SAILFLOW.HTM Tom