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Keyword : optimisation
Results 1 - 5 of 46
Flexible Hydrofoil Optimization for the 35th America's Cup with Constrained Ego Method
We compare the optimized flexible hydrofoil with a rigid foil geometrically optimized for the same sailing conditions. This comparison highlights the hydrodynamical advantages brought by the flexibility: a reduction of the drag over a large range of boat speeds, less susceptibility to cavitation and a smaller angle of attack tuning range.
Bayesian Strategies for Simulation-Based Optimisation and Response Surface Creation Using a Single Tool
Surrogate models are simplified models for the behaviour of a complex system, based on a limited number of operating points where the system behaviour is simulated accurately. In hydrofoil design for sailing yachts, surrogate models can be used both for automatic shape optimisation of the foil and for performance evaluation of the entire yacht in the context of a VPP, as a response surface. We present an adaptive method for the construction of surrogate models which can be used for both these objectives, with a simple change of parameters. A Gaussian process regression (GPR) is used for the data fitting, while the adaptive choice of sample points is based either on the GPR variance or on a combination with a cross-validation error estimation. A first test on analytical functions shows that the cross-validation approach is superior for response surface creation, while both adaptation methods are equally suited for shape optimisation. A second test on the shape optimisation of a two-dimensional hydrofoil indicates thatfor moderate immersion depths, the optimum shape is not sensible to the distance to the free surface.
Prediction and optimization of aerodynamic and hydrodynamic forces and boat speed of foiling catamarans with a wing sail and a jib
This paper describes a method to calculate the
aerodynamic forces generated by a rigid two-element wing
together with a jib. Additionally, investigations of
hydrodynamic flow forces generated by water-piercing Lshaped
foils are introduced. The aerodynamic and
hydrodynamic flow force prediction methods are combined
in a velocity prediction program featuring a constraint
optimization method in order to predict boat speed and wing
and foil trimming parameters for its maximization.
A velocity polar calculated by applying this method to a
50-foot catamaran is shown and the result of some studies
are presented, varying design parameters of the catamaran.
Experimental and numerical trimming optimizations for a mainsail in upwind conditions
This paper investigates the use of meta-models for optimizing sails trimming. A Gaussian process is used to robustly approximate the dependence of the performance with the trimming parameters to be optimized. The Gaussian process construction uses a limited number of performance observations at carefully selected trimming points, potentially enabling the optimization of complex sail systems with multiple trimming parameters. We test the optimization procedure on the (two parameters) trimming of a scaled IMOCA mainsail in upwind conditions. To assess the robustness of the Gaussian process approach, in particular its sensitivity to error and noise in the performance estimation, we contrast the direct optimization of the physical system with the optimization of its numerical model. For the physical system, the optimization procedure was fed with wind tunnel measurements, while the numerical modeling relied on a fully non-linear Fluid-Structure Interaction solver. The results show a correct agreement of the optimized trimming parameters for the physical and numerical models, despite the inherent errors in the numerical model and the measurement uncertainties. In addition, the number of performance estimations was found to be affordable and comparable in the two cases, demonstrating the effectiveness of the approach.
Fully Integrated Fluid-Structural Analysis for the Design and Performance Optimisation of Fibre Reinforced Sails
This paper presents an advanced and accurate integrated
system for the design and performance optimisation of
fibre reinforced sails, commonly named string sails,
developed by SMAR Azure. This integrated design system
allows sail designers not only to design sail shapes and the
reinforcing fibre paths, but also to validate the performance
of the flying sail shape and have accurate production
details including the overall sail weight, material used,
which means costs, and length of the fibre paths, which
means production time.
The SMAR Azure design and analysis method,
extensively validated and used to optimise several racing
and super-yacht sailing plans, includes a computationally
efficient structural analysis method coupled with a
modified vortex lattice method, with wake relaxation, to
enable a proper aeroelastic simulation of sails in upwind
conditions. The structural analysis method takes into
account the geometric non-linearity and wrinkling
behaviour of membrane structures, such as sails, the fibre
layout, the influence of battens, trimming loads and
interaction with rigging elements, e.g. luff sag calculation
on a headstay, in a timely manner.
Specifically, this paper presents an optimisation of a real
fibre reinforced membrane sailplan of an aluminium super
yacht, carried out in collaboration with Paolo Semeraro
(Banks Sails Europe). The optimisation process of the fibre
layouts led to a sensible reduction in maximum stress,
strain and displacement compared to the initial designs,
keeping the same fibre weight or slightly increasing it. The
results have been confirmed in the sailing tests, although no
exact measurements have been performed.