Trans RINA, Vol 153, Part B2, Intl J Small Craft Tech, 2011 Jul-Dec TECHNICAL NOTE


A FULLY INTEGRATED SAIL-RIG ANALYSIS METHOD (DOI No: 10.3940/rina.ijsct.2011.b2.118tn) S Malpede and F Nasato, SMAR Azure, UK SUMMARY


This paper presents a method to analyse the rigs of sailing yachts in a timely, cost-effective and versatile manner. Mast and rig design cover an important role in maximising sailing yacht performance. The design of optimal rigs should consider realistic sail loads; conversely the design of an optimal sail-plan should take into account particular rig configuration and structural behaviour. A method is presented for simulating the structural behaviour of rigs under aeroelastic sails loads in upwind sailing conditions. The method consists of two main components: DESIGN, where rig and sails geometry and materials are defined; ANALYSIS, where the rig is analysed under the calculated sails loads in specified trim and sailing conditions. Design, meshing and analysis phases are fully integrated in a single software platform, which allows the comparison of alternative solutions. The sail-rig analysis is non-linear and can be applied to fibre-membrane sails.


NOMENCLATURE A


AWA AWS CDrive CE


CEz CP


CSide δmax E


EUWS FEM KE


MVLM η p


p∞ ρ


Q∞


RANS σmax


TGWS V


V∞


VLM VPP WTT


1.


Section area of batten (mm2) Apparent Wind Angle (°) Apparent Wind Speed (m s-1) Drive force coefficient Centre of Effort


Centre of Effort height (m) Pressure coefficient Side force coefficient


Maximum displacement (m) Young’s modulus (GPa)


Equivalent Uniform Wind Speed (m s-1) Finite Element Model Element stiffness matrix


Modified Vortex Lattice Method Efficiency, CDrive / CSide


Asymptotic dynamic pressure (N m-2) Reynolds Averaged Navier Stokes Maximum stress (MPa)


Asymptotic flow pressure (N m-2) Density (kg m-3)


Pressure (Pa)


Top Gradient Wind Speed (m s-1) Flow velocity at a control point (m s-1) Asymptotic flow velocity (m s-1) Vortex Lattice Method


Velocity Prediction Program Wind Tunnel Test


INTRODUCTION


This paper has been published in the 2010 RINA INNOV’sail conference [1] and presents a method to optimize the design of modern sailing yacht rigs. The optimization is performed via a fully integrated design and analysis method that predicts the sail-rig aeroelastic behaviour in specific sailing and trimming conditions. Mast and rig design cover an important maximising the performance of


role sailing yachts. The ©2011: The Royal Institution of Naval Architects


design of optimal rigs should take into account realistic sail loads whereas the design of optimal sailplan should consider the particular rig configuration and structural behaviour (mast bend, forestay sag). The challenge is to facilitate both.


The method presented in this paper allows the design of optimal


rigs by virtually behaviour of various simulating the structural rig configurations under the


aeroelastic sail loads in upwind sailing conditions. The method performs the aeroelastic analysis of sails through the interaction of a structural non-linear Finite Element Model (FEM) with a vortex lattice aerodynamic model [2]. The final sail loads, evaluated in defined sailing conditions, and the trim loads are applied to the various rig components. The rig structural analysis is non-linear and takes into account the different structural properties of the rig elements. The method is fully integrated in a single software platform and also supports


fibre-


membrane sails. The main features are:  Geometrical


definition components.


 Creation of an aerodynamic model and FEM of the sailplan.


 Iterative aeroelastic solution for the sailplan.  Rig FEM and structural analysis.


The structural analysis of rigs can be solved with a variety of commercial available finite element analysis software, which requires user defined sail


loads. The in


existing mast design procedures are based almost entirely on designer’s experience. When it is crucial to optimise the sail-rig performance, designers often use RANS codes (Reynolds Averaged Navier Stokes) to calculate the sail loads. Indeed, not only these procedures are very expensive in terms of time and human and technical resources needed, but also it can be very laborious to transfer the sail loads to the rig FEM avoiding numerical errors. At


present no single, standalone and fully B-117 of sail shapes and rig


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