INTERACTIONS BETWEEN TWO FLETTNER ROTORS USED FOR WIND SHIP ASSISTED PROPULSION

Abstract

Wind tunnel tests are carried out at the Aerodynamics Laboratory of the Ecole Nationale des Arts et Métiers (ENSAM) in Paris on 50 mm and 130 mm diameter rotating circular cylinder in infinite aspect ratio or finite aspect ratio of 3 to 6, with or without rotating endplates. Aerodynamic forces are measured by a 5-components balance and by integrating pressures over three sections along the span of the rotating cylinder. The tests carried out at Reynolds numbers between 13,500 and 70,000 are significant and make it possible to dispense tests at high flow speeds. The results, based on pressure measurements, indicate that the rotation of the cylinder drives the fluid in a spiral motion along the span, winding the flow, accompanied by a very strong increase in the drag coefficient between the middle and the top of the cylinder. The interaction between two rotating cylinders, spaced out by 6 diameters, decreases the ratio CL / CD of the thruster reducing its propulsive performance at close wind angles (30°