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Keyword : fluid dynamics
Results 1 - 5 of 32
Fluid Structure Interaction Design Development of Passive Adaptive Composite International Moth Foil
The International Moth is a single-handed ultra-lightweight foiling development class boat, and it fol- lows open class rules. Therefore, the designer and builder have full liberty to develop and produce the fastest boat [1]. It is possible to adapt the internal structure of the fixed foil to achieve a tailored twist angle for a given load. Exploring the possibility of using Passive Adaptive Composite (PAC) on the moth hydrofoil to control its pitch angle enables the boat to achieve a stable flight in a wide range of weather conditions whilst reducing the induced drag, passively decreasing the angle of attack in increased boat speed. Using PAC in a multi-element foil, such as the International Moth one, will allow the structure to achieve a constant lift force with speeds higher than the design take-off speed with less need to con- stantly modifying the rear foil section. Toward the development of a PAC moth fixed foil, experimental and numerical results for a single element aerofoil, able to achieve a linear decrease in lift coefficient with increase in wind speed, are presented and discussed. The results present the aero-elastic response of the foil explaining the complexity involved in fluid-structure interaction problems.
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.
A Comparison of RANS and LES for Upwind Sailing Aerodynamics
Computational methods currently form a significant part
of a sailing yacht design project. The fluid-dynamics that
characterises a sailing yacht is extremely complex, due
to the fact that the yacht is partly immersed in water and
partly in air with major three-dimensional and turbulent
phenomena. A large number of investigations, using both
experimental and numerical methods, have created an
extensive knowledge of the physics of a sailing yacht, but
at the same time highlighted the extent and complexity of
this research field. A better understanding of the physics
involved in both the aerodynamics and fluid dynamics of
the yacht, together with the need to develop, improve and
validate existent numerical models are primary reasons to
further extend the work done on this subject.
There have been a number of studies of the aerodynamics
of upwind sails. Viola (Viola et al., 2013) modelled the air
flow field around a hypothetical AC33 class yacht design,
using a steady RANS solver, and highlighted the main
flow features and structures involved in upwind sailing
aerodynamics. Even though the flow is mainly attached to
the sails, numerical results showed areas of leading edge
flow separation, especially at the top of the mainsail, where
the influence of the downwash generated by the headsail is
less predominant. Querard & Wilson (Querard & Wilson,
2007) and Masuyama (Masuyama et al., 2007) showed
the need for a high quality, fine mesh in order to capture
these flow features and correctly reproduce the pressure
distribution on the sail surface. Queutey (Queutey et al.,
2015) addressed some misbehaviour of numerical models to
geometric incongruities with the experimental benchmark
model.
The present work further investigates upwind sailing
aerodynamics, analysing the effects of geometric and
mesh modifications, in combination with the use of Large
Eddy Simulation. LES has proven its ability to model
highly turbulent and separated flow (Sagaut & Mary,
2001) (Sampaio et al., 2014), albeit at the expense of high
computational costs. To date there are no published results
of LES in sailing aerodynamics, and so the application of
the methodology to the modelling of a well documented
experiment (Fluck, 2010) allows the testing of LES’s
capabilities and applicability to this field of research.
A high resolution grid was used so as to capture the finest
flow structures trying to correctly reproduce the pressure
distribution across the sails, especially in regions of flow
separation. Particular effort was made to replicate the experimental
test conditions and to analyse the influence that
different set ups have on the computational results. Simulations
were performed using RANS and LES on the same
mesh, allowing a direct comparison between the methods.
High Performance Sailing in Olympic Classes - A Research Outlook and Proposed Directions
The purpose of this paper is to explore research opportunities in Olympic sailing classes. Olympic classes provide highperformance
sailing using a diversity of equipment, with the understanding that the equipment, individual athletes, and the
knowledge relating to those two factors impacts performance. Thus, the Olympic motto, “Citius, Altius, Fortius” (Latin for “Faster,
Higher, Stronger”), governs everyday life for many engineers. During the last few years, Chalmers has supported a project that
focuses on the possibilities and challenges for research combined with engineering knowledge in the area of sports. The initiative has
generated external funding and gained great acclaim within Chalmers, among staff and students, in the Swedish sports movement,
and in large companies, as well as within small and medium sized enterprises. The project focuses on five sports: swimming,
equestrian events, floorball, athletics, and sailing. The contribution from this paper describes an outlook identifying eight areas
containing research opportunities: sailing dynamics, how to sail in Olympic classes, fluid structure interaction, surface structures,
turbulence induction on the rig, equipment in Olympic classes, and applying game theory to sailing.
