This work is part of the VOILENav project which aims to improve the understanding of Fluid-Structure Interaction applied to sails. Full-scale numericalexperimentalcomparisons are achieved in upwind conditions with a...
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This work is part of the VOILENav project which aims to improve the understanding of Fluid-Structure Interaction applied to sails. Full-scale numericalexperimentalcomparisons are achieved in upwind conditions with an inviscid flow code. A criterion using the equilibrium between the righting and heeling moment is suggested to check the attached flow hypothesis. Previous full- scale studies on instrumented boat are limited by the natural unsteadiness of wind and sea conditions and the measurement of these conditions. True wind computation and the wide range of encountered sailing conditions are still challenging. Complementary wind tunnel tests are carried out in this PhD project, using controlled conditions, to address some issues observed at full-scale. Thanks to the Sailing Fluids collaboration, two experimental campaigns in the Twisted Flow Wind Tunnel of the Yacht Research Unit of the University of Auckland have investigated upwind and downwind conditions. Upwind tests investigate static and dynamic trimming on three model IMOCA60 mainsails. The optimum static trim is determined thanks to an innovative optimization algorithm then the pumping amplitude and frequency are investigated. Aerodynamic performances under dynamic trimming are better than the optimum static trim with a maximum located for a reduced frequency about 0.25 to 0.3. For the downwind test, the natural unsteadiness known as curling (repeated folding- unfolding of leading edge) is studied. Four model J80 spinnakers with identical design shape are tested with different materials and cuts. Wind tunnel measurements show that for apparent wind angles higher than 100°, the curling apparition increases the drive force by up to 10%. Wind speed and wind angle effects are investigated and show a reduced curling frequency of 0.4 independent from the flow velocity for an apparent wind angle of 120°. The variety of the experimental conditions tested makes this work a precious database for Fluid Structure Int
A numerical investigation of the dynamic Fluid-Structure Interaction (FSI) of a yacht sail plan submitted to harmonic pitching is presented to address both issues of aerodynamic unsteadiness and structural deformation...
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A numerical investigation of the dynamic Fluid-Structure Interaction (FSI) of a yacht sail plan submitted to harmonic pitching is presented to address both issues of aerodynamic unsteadiness and structural deformation. The FSI model - Vortex Lattice Method fluid model and Finite Element structure model - have been validated with full-scale measurements. It is shown that the dynamic behaviour of a sail plan subject to yacht motion clearly deviates from the quasi-steady theory. The aerodynamic forces presented as a function of the instantaneous apparent wind angle show hysteresis loops, suggesting that some energy is exchanged by the system. The area included in the hysteresis loop increases with the motion reduced frequency and amplitude. comparison of rigid versus soft structures shows that FSI increases the energy exchanged by the system and that the oscillations of aerodynamic forces are underestimated when the structure deformation is not considered. Dynamic loads in the fore and aft rigging wires are dominated by structural and inertial effects. This FSI model and the obtained results may be useful firstly for yacht design, and also in the field of auxiliary wind assisted ship propulsion, or to investigate other marine soft structures. (c) 2013 Elsevier Ltd. All rights reserved.
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