Unsteady pressure measurements at sea on the rigid wings of a model wind propelled ship. Part A: Measurement system development

• Model scale tests of a wind powered car carrier in real conditions at sea. • Pressure measurements on rigid wings in unsteady wind. • Experimental lift curves show a strong dependence on unsteady effects. The in-situ measurement of aerodynamic parameters on a boat evolving in natural conditions can be challenging. Nonetheless, the development of wind assistance and propulsion for cargo vessels calls for new methods to ensure the broadest possible evaluation of the aerodynamic interaction effects between the wind propulsion units and between the units and the hull. This paper proposes an experimental approach based on a scaled model of the Oceanbird concept car-carrier sailing at sea, in real conditions. A pressure measurement system was developed at KTH Royal Institute of Technology, which consists of 66 differential pressure sensors installed inside one of the four rigid wings. The capabilities and limitations of this sensor suite are explored in this article. With the implementation of specific experiments with the wings, we show that the system can detect stall and its hysteresis loop, as well as wing-wing and wing-hull interaction effects. The main limitation for the full aerodynamic characterisation of the boat comes from the lack of simultaneous measurement on all wings, which will be addressed in a second part of this paper.