Improving the Downwind Sail Design Process by Means of a Novel FSI Approach

Antonino Cirello,Davide Tumino,Antonio Mancuso,Vincenzo Nigrelli,Tommaso Ingrassia

doi:10.3390/jmse9060624

Abstract

The process of designing a sail can be a challenging task because of the difficulties in predicting the real aerodynamic performance. This is especially true in the case of downwind sails, where the evaluation of the real shapes and aerodynamic forces can be very complex because of turbulent and detached flows and the high-deformable behavior of structures. Of course, numerical methods are very useful and reliable tools to investigate sail performances, and their use, also as a result of the exponential growth of computational resources at a very low cost, is spreading more and more, even in not highly competitive fields. This paper presents a new methodology to support sail designers in evaluating and optimizing downwind sail performance and manufacturing. A new weakly coupled fluid–structure interaction (FSI) procedure has been developed to study downwind sails. The proposed method is parametric and automated and allows for investigating multiple kinds of sails under different sailing conditions. The study of a gennaker of a small sailing yacht is presented as a case study. Based on the numerical results obtained, an analytical formulation for calculating the sail corner loads has been also proposed. The novel proposed methodology could represent a promising approach to allow for the widespread and effective use of numerical methods in the design and manufacturing of yacht sails.

Highlights

The exponential growth of computational resources at a very low cost has allowed for the widespread use of numerical methods in the nautical field as well as at an industrial level, for scientific research or highly competitive purposes
To date, advanced numerical methods are commonly used in the nautical field only for competitive applications, but it is conceivable that in the future these methods could be used in other application fields
To improve sail design and to better understand sail aerodynamics, numerical simulations and experimental testing are the most used and reliable methods [2,3,4,5]. These methods have led to a better comprehension of the complex phenomena and the physics underlying sailing and, through them, a remarkable increase of the performances of yacht sails has been obtained in recent years [6,7]

Summary

Introduction

The exponential growth of computational resources at a very low cost has allowed for the widespread use of numerical methods in the nautical field as well as at an industrial level, for scientific research or highly competitive purposes. To improve sail design and to better understand sail aerodynamics, numerical simulations and experimental testing are the most used and reliable methods [2,3,4,5] These methods have led to a better comprehension of the complex phenomena and the physics underlying sailing and, through them, a remarkable increase of the performances of yacht sails has been obtained in recent years [6,7]. The authors propose calculating the flying shape and the loads on downwind sails, to estimate propulsive forces [2,10], and to help sailmakers in dimensioning and defining the best arrangement of the sail reinforcements For this purpose, a weakly coupled FSI procedure [16] is used to find the real flying shape and to estimate the loads on the head, the clew, and the tack of the sail when the sailing conditions change. On the basis of the numerical results obtained, an analytical formulation for the calculation of the forces on the sail is proposed

Materials and Methods

FSI Procedure

Findings

Loads on the Corners of the Sail