A Novel Experimental Approach to the Aerodynamic Testing of Wind Assisted Ship and Yacht Sails

Highly cambered profiles yield powerful wind-assisted ship wings and yacht sails. However, their complex aerodynamics governed by flow separation remains to be fully understood. Particle image velocimetry in water tunnels may lead to new breakthroughs, but limitations exist due to the necessary high spatial and temporal resolution. Force measurements and flow visualisation were undertaken on circular arcs and sails to ascertain the viability of this novel experimental approach. The results reveal that (i) a linear blockage correction can be devised; (ii) a blockage-independent critical Reynolds number and critical angle of attack exist; and (iii) a force crisis occurs because of the suppressed laminarization of the boundary layer downstream of the leading-edge separation bubble. Ultimately, water tunnel testing is demonstrated to be a pertinent experimental methodology. These findings provide novel insights into the experimental testing of wind-assisted ship and yacht sails, and may contribute to improving their performance by design.