The aerodynamics of symmetric spinnakers

Lasher, William C.; Sonnenmeier, James R.; Forsman, David; Tomcho, Jason

doi:10.1016/j.jweia.2005.02.001

Cited by 17 publications

(6 citation statements)

References 12 publications

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“…• Lasher et al (2005) investigate rigid spinnaker models in order to avoid a complex fluid structure interaction, and note that a soft sail might collapse before reaching the point of maximum lift used on a beam reach. They highlight that testing soft sails is necessary to determine how this would impact their results.…”

Section: Closely Related Previous Workmentioning

confidence: 99%

Performance enhancement of downwind sails due to leading edge flapping: A wind tunnel investigation

et al. 2018

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This work presents a wind tunnel experimental study on the effect of the leading edge flapping on the aerodynamic performance of a spinnaker. Four J80-class spinnaker models, combining two different assembling structures (panel layout) and two different sail materials are tested at various wind speeds and wind angles in a wind tunnel. Results show that, for the wind angle range the spinnaker is designed for, the sustained periodic flapping of the sail leading edge has a significant benefit on performance, with 10% increase in drive force. In these model-scale tests, the sail structural properties did not show significant differences in performance, but affect the point where flapping sets in: a model with a stiffer material and a cross-cut panel layout starts flapping for a longer sheet length, compared to a lighter cloth and a tri-radial layout. Finally, it is shown that the nondimensional flapping frequency is rather constant 0.4 in the design range of wind angle, but it varies with the wind speed and sail structural properties on a smaller wind angle where the spinnaker is more stretched.

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Section: Closely Related Previous Workmentioning

confidence: 99%

Performance enhancement of downwind sails due to leading edge flapping: A wind tunnel investigation

et al. 2018

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“…Examples of such wings are downwind yacht sails, or spinnakers. They operate near stall and feature significant trailing-edge separation (Lasher, 2001;Lasher et al, 2005;Viola & Flay, 2012;, Souppez et al, 2022. As a result, typical wind tunnel blockage corrections such as that of Pope & Harper (1966) do not prove suitable.…”

Section: Introductionmentioning

confidence: 99%

Development of a Blockage Correction for Highly Cambered 2D Circular Arcs

Souppez

Viola

2022

Day 1 Fri, June 10, 2022

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Model-scale testing of yacht sails and wings often suffers from blockage due to the physical constraints of experimental facilities. With blockage, a greater increase in flow speed occurs in the vicinity of the geometry compared to an unblocked flow as a direct consequence of the restricted cross-sectional area. This leads to artificially higher forces, making comparison and validation between tests conducted in different facilities difficult, while also flawing performance prediction if the forces are not suitably corrected. Blockage correction for streamlined bodies and bluff bodies such as flat plates normal to the flow, are well-established. However, it is not the case for lift-generating bluff bodies, or lifting body, experiencing high trailing-edge separation, such as highly cambered plates and downwind yacht sails. This study focusses on the development of a blockage correction for highly cambered plates, specifically circular arcs, comparable to horizontal sections of downwind yacht sails. Measurements are undertaken at positive incidences below deep-stall for Reynolds numbers ranging from 53,530 to 218,000 in a towing tank and a water tunnel to devise a blockage correction. The critical impact of the free surface deformation on wake blockage is evidenced. This allows to set a maximum limit to the amount of blockage a cambered plate can experience before blockage correction is no longer accurate, hence the importance of closed measurement sections to prevent free surface deformation. Furthermore, the experiments revealed that flow behaviours such as the laminar-to-turbulent transition are preserved even with high blockage. The angle of attack at which transition occurs is also preserved in pressurized wind tunnel tests. However, the effect on the forces cannot be fully corrected, and thus further work would be needed to extend the applicability of the proposed blockage correction to such facilities. These findings provide experimental insights into the effect of blockage on highly cambered plates, and it is anticipated they will support future force experiments conducted on high-camber plates and downwind sails in water tunnels.

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“…Upwind sails, where the flow remains largely attached, have been successfully analysed using inviscid codes since the 1960s, with the pioneering work of Milgram (1968) on Vortex Lattice Method (VLM), and later Gentry (1971), to eventually be extensively utilized in America's Cup sails development (Gentry, 1988). Conversely, for downwind sails, where the flow is largely separated, the use of Reynolds-Averaged Navier-Stokes (RANS) simulations is necessary (Lasher et al, 2005). The first instances of RANS occurred in 1996 for downwind sails (Hedges et al, 1996) and 1999 for upwind sails (Miyata & Lee, 1999).…”

Section: Introductionmentioning

confidence: 99%

Recent Advances in Numerical and Experimental Downwind Sail Aerodynamics

Souppez

Arredondo-Galeana

Viola

2019

Journal of Sailing Technology

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Over the past two decades, the numerical and experimental progresses made in the field of downwind sail aerodynamics have contributed to a new understanding of their behaviour and improved designs. Contemporary advances include the numerical and experimental evidence of the leading-edge vortex, as well as greater correlation between model and full-scale testing. Nevertheless, much remains to be understood on the aerodynamics of downwind sails and their flow structures. In this paper, a detailed review of the different flow features of downwind sails, including the effect of separation bubbles and leading-edge vortices will be discussed. New experimental measurements of the flow field around a highly cambered thin circular arc geometry, representative of a bi-dimensional section of a spinnaker, will also be presented here for the first time. These results allow interpretation of some inconsistent data from past experiments and simulations, and to provide guidance for future model testing and sail design.

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The aerodynamics of symmetric spinnakers

Cited by 17 publications

References 12 publications

Performance enhancement of downwind sails due to leading edge flapping: A wind tunnel investigation

Performance enhancement of downwind sails due to leading edge flapping: A wind tunnel investigation

Development of a Blockage Correction for Highly Cambered 2D Circular Arcs

Recent Advances in Numerical and Experimental Downwind Sail Aerodynamics

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