Modelling leading edge separation on a flat plate and yacht sails using LES

This work presents an investigation into the aerodynamics of upwind sailing using different methods of modelling turbulence, comparing Large Eddy Simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS) methods. A preliminary simulation of a flat plate at an angle of attack was performed in order to investigate the potential for LES in modelling flows around a sharp leading edge. Comparison with existing experimental data highlighted the formation of a double recirculation bubble structure at the leading edge that only LES was able to predict. However, a fine mesh and small timestep are required to correctly reproduce the pressure distribution on the flat plate. The RANS and LES models were subsequently used to model an upwind sail geometry tested in the wind tunnel. The CFD results showed good agreement with the experimental data and in particular highlighted the superior performance of the LES model in predicting the leading edge recirculation structure compared to RANS. The solution was sensitive to the mesh and timestep used. A mesh size of order y(+) similar to 1 and a Courant number <= 1 provided results with RMS errors less than 0.1 between the simulation and the experimental values of the coefficients of pressure at the top of the mainsail. (C) 2016 Elsevier Inc. All rights reserved.