Development of a wind tunnel test facility for yacht aerodynamic studies

摘要

Wind-tunnel tests on scale models of yachts are very difficult to carry out accurately because of the complicated aerodynamics and boundary conditions associated with the full-scale situation. Yachts sail at the interface between water and air. The water surface is not smooth, and the yacht orientation and wind strength vary with time. In addition, the sails behave somewhat like slender aerofoils for some sailing directions, and whereas like bluff bodies at others. This paper addresses some of the simplifying assumptions which must be made in order to make practical wind tunnel measurements on scale models of yachts. It describes a wind tunnel and balance facility which has been developed in the Mechanical Engineering Department of the University of Auckland to measure and process the aerodynamic forces and moments generated by wind flowing over yacht sails. The development of a linerised version of Galway's force balance calibration method to process the balance data is described. This simplified version confers significant advantages in the real-time operation of the balance. Finally, the usefulness of the facility is illustrated with some results obtained during the study of a Twelve Metre America's Cup Yacht sailing downwind under spinnaker.