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Keyword : performance assessment
Results 1 - 5 of 70
Performance Evaluation and Ranking of 7 Rudders for the Finn Dinghy
As a follow up to the Olympic Games, 7 commercially available Finn dinghy rudders were tested to determine their hydrodynamic performance. The 7 tested rudders make up 78% of the rudders that were measured for competition at the 2016 Olympic Games, thus representing a large portion of the rudders used by sailors. The remaining two not tested are of semi-custom or custom design or manufacture. All rudders were tested in 7 different conditions, selected to cover a wide range of sailing conditions. The testing revealed considerable differences, both in performance and handling.
Experimental Set Up for Measuring Onshore and Onboard Performances of Leading Edge Inflatable Kites - Presentation of Onshore Results
This paper describes an experimental set up aiming to control and measure performances of small leading edge inflatable kite (lower than 12m2). This set up can be deployed onshore or on a dedicated boat. Two experimental campaigns were achieved using this set-up, one onshore in June 2016, and the second one at sea on April 2017. This paper focuses on the first one, and after a detailed presentation of sensors, it presents an specific post processing of the data including phase averaging. The guideline of this work is to estimate the variation of the lift coefficient and lift to drag ratio along 8-pattern trajectories. Results show a loss of lift coefficient of about 20% of the maximum value during kite turn. The the lift to drag ratio evolution along a trajectory is also going through a local minima during kite turn (even if global evolution is questionable and still need further work). Nevertheless these trends still require the post processing of the whole experimental database, in order to be confirmed and properly interpreted.
A Comparison of a RANS Based VPP to on the Water Sailing Performance
This paper compares performance predictions from a
Reynolds Averaged Navier Stokes (RANS) based Velocity
Prediction Program (VPP) to on the water testing of a J70.
The J70 has been outfitted with a system to determine sail
flying shapes, apparent wind conditions and performance
data. The on the water testing is conducted in both racing
and controlled sailing conditions. Data taken during racing
conditions is analyzed to determine optimal performance
envelopes while data taken in controlled conditions is used
to match exact sailing and VPP states. The data acquisition
system combines a number of standard marine sensors
including a sonic anemometer, a GPS, a digital compass, an
accelerometer and a gyroscope with custom sensors that
measure rudder and boom angles as well as a custom sail
shape acquisition system. The RANS based VPP developed
by Doyle CFD has three main components; an aerodynamic
force model, a hydrodynamic force model and an algorithm
to balance the forces. The force balance routine uses four
degrees of freedom; boat speed, yaw, heel and rudder angle
to balance the aerodynamic and hydrodynamic forces for a
given true wind speed and angle. The force models are
derived from RANS CFD data calculated using
OpenFOAM. The aerodynamic forces are calculated using
steady state RANS as a function of apparent wind angle,
apparent wind speed and sail flying shape. The VPP force
model is derived by fitting response surfaces to this data.
The aerodynamic CFD is run with sail flying shapes
recorded from on the water testing. Using accurate flying
shapes is critical for picking out slight aerodynamic
differences in sail and rig setup. The hydrodynamic CFD
data points are calculated using RANS Volume of Fluid
CFD (VOF) as a function of boat speed, rudder angle, yaw
angle, heel angle and displacement. Response surfaces are
generated from a 128 data point array of RANS VOF
simulations.
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.
The Influence of Sailor Position and Motion on the Performance Prediction of Racing Dinghies
The time-varying influence of a sailor’s position is
typically neglected in dinghy velocity prediction programs
(VPPs). When applied to the assessment of dinghy race
performance, the position and motions of the crew become
significant but are practically hard to measure as they
interact with the motions of the sailboat. As an initial stage
in developing a time accurate dinghy VPP this work
develops an on-water system capably of measuring the
applied hiking moment due to the sailor’s pose and
compares this with the resultant dinghy motion. The
sailor’s kinematics are captured using a network of inertial
motion sensors (IMS) synchronised to a video camera and
dinghy motion sensor. The hiking moment is analysed
using a ‘stick man’ body representation with the mass and
inertial terms associated with the main body segments
appropriately scaled for the representative sailor. The
accuracy of the pose captured is validated using laboratory
based pose measurements. The completed work will
provide a platform to model how sailor generated forces
interact with the sailboat to affect boat speed. This will be
used alongside realistic modelling of the wind and wave
loadings to extend an existing time-domain dynamic
velocity prediction program (DVPP). The results are
demonstrated using a single handed Laser and demonstrate
an acceptable level of accuracy.