Numerical study of a flexible sail plan submitted to pitching: Hysteresis phenomenon and effect of rig adjustments

Abstract

A numerical investigation of the dynamic Fluid Structure Interaction (FSI) of a yacht sail plan submitted to harmonic pitching is presented to analyse the system's dynamic behaviour and the effects of motion simplifications and rigging adjustments on aerodynamic forces. It is shown that the dynamic behaviour of a sail plan subject to yacht motion clearly deviates from the quasi-steady theory. The aerodynamic forces presented as a function of the instantaneous apparent wind angle show hysteresis loops. It is shown that the hysteresis phenomenon dissipates some energy and that the dissipated energy increases strongly with the pitching reduced frequency and amplitude. The effect of reducing the real pitching motion to a simpler surge motion is investigated. Results show significant discrepancies with underestimated aerodynamic forces and no more hysteresis when a surge motion is considered. However, the superposition assumption consisting in a decomposition of the surge into two translations normal and collinear to the apparent wind is

Development of a 6-DOF Dynamic Velocity Prediction Program for offshore racing yachts

“…The work of Tuckerman (1926) is used to derive a three-dimensional effect factor that proved rather consistent when compared to experimental measurements on a model sail by Gerhardt et al (2009). As was shown by Fossati andMuggiasca (2011), Gerhardt et al (2011) and Augier et al (2014), such simple models do not fully reproduce the unsteady aerodynamic behavior of sails, and especially hysteresis phenomena. Further work still needs to be carried out to integrate such aspects in DVPPs if higher relative frequencies are to be considered.…”

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

“…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. Nevertheless, wind tunnel testing violates some rules of similitudes as Reynolds number, the ratio of fabric weight or membrane stress to wind pressure (Flay, 1996) and cannot reproduce properly all the physical phenomena present at full-scale.…”

Modal Analysis of Pressures on a Full-Scale Spinnaker

“…. Nowadays, advanced computational resources have enhanced numerical simulation and have allowed coupling of fluid and structural solvers to create Fluid-Structure Interaction simulations (Renzsch and Graf 2010;Chapin et al 2011;Lombardi et al 2012;Ranzenbach et al 2013;Trimarchi et al 2013;Augier et al 2014;Durand et al 2014). However, wind tunnel testing and full-scale testing are required for comparison and validation (Hansen et al 2002;Viola and Flay 2011;Renzsch and Graf 2013).…”