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Keyword : wind tunnel tests
Results 1 - 5 of 55
Full Scale Pressure Measurements From SYL Navigation: An Upwind Case Study
The present work discusses an upwind case study about full scale measurements gathered during navigation on the Politecnico di Milano Sailing Yacht Laboratory (SYL). SYL is a 10m sailing boat, consisting in standard instrumentation, integrated dynamometer, a 3D flying shape detection system and distributed pressure sensors on sails. Particular attention was devoted to pressure measurements: full scale results are analysed and compared with wind tunnel test. The comparison of full scale/wind tunnel pressure distributions holds consistently, with the highest differences observed in the regions close to the leading edge. Critical aspects related to performing full scale measurements are also discussed.
To Curl or Not to Curl: Wind Tunnel Investigations of Spinnaker Performance
This work presents a wind tunnel experimental study of the effect of curling on the spinnaker aerodynamic performance. Four spinnakers combining two different panellings and sail materials are tested at different wind speeds and wind angles in the Twisted Flow Wind Tunnel of the University of Auckland. Results show that the curling has a significant benefit on the propulsive force at an AWA ≥ 100◦ when this conclusion cannot be made at lower AWA where the best propulsive force is reached on the verge of curl- ing or before. Sail material and panelling have an effect on the sheet length where curling appears, stiffer material and cross cut panelling being the latest to curl. Finally, it is shown that the curling frequency increased linearly with the flow speed at AWA = 120◦.
Pressure Measurements on Yacht Sails: Development of a New System for Wind Tunnel and Full Scale Testing
The paper presents an overview of a joint project
developed among Politecnico di Milano, CSEM and North
Sails, aiming at developing a new sail pressure measurement
system based on MEMS sensors (an excellent compromise
between size, performance, costs and operational
conditions) and pressure strips and pads technology. These
devices were designed and produced to give differential
measurement between the leeward and windward side of the
sails. The project has been developed within the Lecco
Innovation Hub Sailing Yacht Lab, a 10 m length sailing
dynamometer which intend to be the reference
contemporary full scale measurement device in the sailing
yacht engineering research field, to enhance the insight of
sail steady and unsteady aerodynamics [1].
The pressure system is described in details as well as the
data acquisition process and system metrological validation
is provided; furthermore, some results obtained during a
wind tunnel campaign carried out at Politecnico di Milano
Wind Tunnel, as a benchmark of the whole measuring
system for future full scale application, are reported and
discussed in details.
Moreover, the system configuration for full scale testing,
which is still under development, is also described.
Wind Tunnel Investigation of Dynamic Trimming on Upwind Sail Aerodynamics
An experiment was performed in the Yacht Research Unit’s
Twisted Flow Wind Tunnel (University of Auckland) to test
the effect of dynamic trimming on three IMOCA 60 inspired
mainsail models in an upwind (AWA = 60) unheeled configuration.
This study presents dynamic fluid structure interaction
results in well controlled conditions (wind, sheet
length) with a dynamic trimming system. Trimming oscillations
are done around an optimum value of CFobj previously
found with a steady trim. Different oscillation amplitudes
and frequencies of trimming are investigated. Measurements
are done with a 6 component force balance and
a load sensor giving access to the unsteady mainsail sheet
load. The driving CFx and optimization target CFobj coefficient
first decrease at low reduced frequency fr for quasisteady
state then increase, becoming higher than the steady
state situation. The driving force CFx and the optimization
target coefficient CFobj show an optimum for the three
different design sail shapes located at fr = 0:255. This optimum
is linked to the power transmitted to the rig and sail
system by the trimming device. The effect of the camber
of the design shape is also investigated. The flat mainsail
design benefits more than the other mainsail designs from
the dynamic trimming compared to their respective steady
situtation. This study presents dynamic results that cannot
be accurately predicted with a steady approach. These results
are therefore valuable for future FSI numerical tools
validations in unsteady conditions.
Evaluation of Multi-Element Wing Sail Aerodynamics from Two-Dimensional Wind Tunnel Investigations
Following the 33rd America's Cup which featured a trimaran versus a catamaran, and the recent 34th America's Cup in 2013 featuring AC72 catamarans with multi-element wing sail yachts sailing at unprecedented speeds, interest in wing sail technology has increased substantially. Unfortunately there is currently very little open peer-reviewed literature available with a focus on multi-element wing design for yachts. The limited available literature focuses primarily on the structures of wings and their control, rather than on the aerodynamic design. While there is substantial available literature on the aerodynamic properties of aircraft wings, the differences in the flow domains between aeroplanes and yachts is significant. A yacht sail will operate in aReynolds number range of 0.2 to 8 million while aircraft operate regularly in excess of 10 million. Furthermore, yachts operate in the turbulent atmospheric boundary layer and require high maximum lift coefficients at many apparent wind angles, and minimising drag is not so critical. This paper reviews the literature on wing sail design for high performance yachts and discusses the results of wind tunnel testing at the Yacht Research Unit at the University of Auckland. Two wings with different symmetrical profiles have been tested at low Reynolds numbers with surface pressure measurements to measure the effect of gap geometry, angle of attack and camber on a wing sail’s performance characteristic. It has been found that for the two element wing studied, the gap size and pivot point of the rear element have only a weak influence on the lift and drag coefficients. Reynolds number has a strong effect on separation for highly cambered foils.