CFD prediction of steady and unsteady upwind sail aerodynamics

In this paper, RANS CFD simulations of steady and unsteady upwind sail aerodynamics are verified and validated against wind tunnel experiments previously performed at Politecnico di Milano. Experimental data is presented, and the experimental results are analysed to estimate repeatability. Blockage effects caused by tunnel boundary layers and measurement equipment are estimated using detailed CFD simulations, allowing such effects to be accounted for. A verification procedure is performed, resulting in very low numerical uncertainties. The force predictions are then validated for both steady and unsteady conditions. The steady results show very good agreement, with a maximum error of 3.1%. For the unsteady conditions, good agreement is found for the force mean values, whilst the prediction of force amplitudes is less satisfactory.