Sail pressures from full-scale, wind-tunnel and numerical investigations

Abstract

The main results of a two-year project aimed at comparing full-scale tests, wind tunnel tests, and numerical analysis predictions are presented. Pressure measurements were obtained from both fullscale tests and wind-tunnel tests, in upwind and downwind conditions. The upwind wind-tunnel test condition was modelled using a Vortex Lattice code, while the downwind wind-tunnel test was modelled using a Navier-Stokes code. The pressures obtained from the three different methods are compared on three horizontal sections of the headsail, mainsail, and asymmetric spinnaker. In general the pressures from the three experiments showed good agreement. In particular, very good agreement was obtained between the numerical computations and the wind tunnel test results. Conversely, the results from the downwind full-scale pressure measurements showed less similarity due to a slightly tightened trim being used for the spinnaker in the on-water tests. Full-scale tests allow the action of unsteadiness due to the wind, wave and yacht movements to affect the results. This unstable environment caused the asymmetric spinnaker to move around, and a tightened trim was required to prevent the spinnaker from collapsing.

The leading-edge vortex of yacht sails

“…The sail trim that allowed the maximum driving force, was used to build a rigid sail with embedded pressure taps and both forces, and pressures were measured in a wind tunnel [20]. This sail trim was also modelled with Reynoldsaveraged Navier-Stokes (RANS) simulations [21] and with DES [16]. A 1:3 rd -scale prototype was built and tested on water on a Platu25-class yacht [22], where surface pressures were measured.…”

“…A 1:3 rd -scale prototype was built and tested on water on a Platu25-class yacht [22], where surface pressures were measured. A tri-way comparison between the pressures measured in a wind tunnel, on water and with RANS was presented in Viola and Flay [21]. While a comparison between wind tunnel tests performed with flexible and rigid sails, and DES, was presented in both [20] and [16].…”

Experimental analysis of a strong fluid–structure interaction on a soft membrane—Application to the flapping of a yacht downwind sail

“…Wind tunnel is commonly used to control the aerodynamic and motion environment of yacht. It has been subject to a large number of experimental studies to measure both the aerodynamic loads on the boat frame using a balance (Flay, 1996;Viola and Flay, 2009;Fossati and Muggiasca, 2011;Campbell, 2014) and the pressure and 3D shape deformation of the structure (Graf and Müller, 2009;Viola and Flay, 2011;Viola et al, 2013). Recent studies have highlighted the non-trivial effect of dynamic oscillation on the aerodynamic forces (Gerhardt et al, 2011;Fossati and Muggiasca, 2011;Augier et al, 2013Augier et al, , 2014a.…”

Study on a Comprehensive Energy-Saving Sail by CFD Method

“…Computational Fluid Dynamic (CFD), a kind of numerical methods, is widely used in the design process of sail due to its advantages and the improvement of computational capacity of computers. Viola [9] and Richard [10] analyze the hydrodynamic performance of two America's Cup design candidates, and the verification and validation show that CFD is accurate and scientific; likewise, Jon and Herve, [11] Y. Tahara and Y. Masuyama [12] prove the reliability and many advantages of Reynolds-Averaged Navier-Stokes (RANS)-based CFD methods.…”