Wind tunnel tests on model of ship with sails

The National Ship Design and Research Centre (NSDRC) has undertaken a project on 'sails as auxiliary means of propulsion of ships'. As part of this research, NSDRC requested IIT, Madras to conduct tests in wind tunnel on sail models singly and in combination with the ship model. In this paper the results pertaining to the latter, ie, ship model with sails are presented. A one meter long model of a ship with two sails of chord 0.097 m and 0.119 m span are tested in wind tunnel. The sails have a camber of 1:8. The forces acting on the model for typical values of the heading angle, β, and the angle of attack, α, of sail were obtained from the wind tunnel balance. To stimulate the effect of roll separate tests were carried out on sail alone with support structure inclined for 3 values of roll angle (γ) viz, of 5°, 8° and 11°. The results show that (a) the optimum angle of sail indicated by tests with sail alone are nearly the same for sail and ship combination, (b) the chosen height of the mast between the sail and the ship is adequate to eliminate the interference between the sail and ship, (c) the effect of γ between 5° and 11° is marginal causing only a slight decrease in the forces of about 7%.