Database of Sail Shapes vs. Sail Performance and Validation of Numerical Calculation for Upwind Condition

Abstract

Database of full-scale three-dimensional sail shapes are presented with the aerodynamic coefficients for the upwind condition of IMS type sails. Three-dimensional shape data are used for the input of numerical calculations and the results are compared with the measured sail performance. The sail shapes and performance are measured using a sail dynamometer boat Fujin. The Fujin is a 34-foot LOA boat, in which load cells and charge coupled devices (CCD) cameras are installed to measure the sail forces and shapes simultaneously. The sailing conditions of the boat, such as boat speed, heel angle, wind speed, wind angle, and so on, are also measured. The tested sail configurations are as follows: mainsail with 130% jib, mainsail with 75% jib and mainsail alone. Sail shapes are measured at several height positions. The measured shape parameters are chord length, maximum draft, maximum draft position, entry angle at the luff and exit angle at the leech. From these parameters three-dimensional coordinates of the sails are calculated by interpolation. These three-dimensional coordinates are tabulated with the aerodynamic coefficients. Numerical calculations are performed using the measured sail shapes. The calculation methods are of two types; Reynolds-averaged Navier-Stokes (RANS)-based CFD and vortex lattice methods (VLM). A multi-block RANS-based CFD method was developed by one of the authors and is capable of predicting viscous flows and aerodynamic forces for complicated sail configuration for upwind as well as downwind conditions. Important features of the numerical method are summarized as follows: a Finite- Analytic scheme to discretize transport equations, a PISO type velocity-pressure coupling scheme, multi-block domain decomposition capability, and several choices of turbulence models depending on flows of interest. An automatic grid generation scheme is also included. Another calculation method, the vortex lattice method is also adopted. In this case, step-by-step calculations are conducted to attain the steady state of the sail in steady wind. Wake vortices are generated step-by-step, which flow in the direction of the local velocity vector. These calculated sail forces are compared with the measured one, and the validity of the numerical method is studied. The sail shape database and comparison with numerical calculations will provide a good benchmark for the sail performance analysis of the upwind condition of IMS type sails.

Numerical and Experimental Studies of Sail Aerodynamics

“…The methodology to achieve the goal of this investigation has been reproducing the full-scale tests described in [30], [31] and [32]. Three sail arrangements have been simulated specifically with the commercial packages ANSYS-CFX and CD-Adapco's STAR-CCM+.…”

“…The methodology to achieve the goal of the investigation presented in this chapter has been reproducing the full-scale measurements obtained from the previously mentioned paper [31] together with [30] and [32]. Yutaka Masuyama and Toichi Fukasawa built the sail dynamometer boat Fujin (figure 6.1) in the late 90s, as mentioned before in chapter 3.…”

“…In 1997 Masuyama and Fukasawa built the sail dynamometer boat Fujin that was similar to the MIT dynamometer. The results using IACC and IMS type sail were reported in different papers such as [30], [31] and [32]. One of the most recent project was initiated in Germany in which the 10-meter full scale sail force dynamometer was named DYNA.…”

“…• Masuyama et al 2007 [31] and 2009 [32]. A database of full-scale three-dimensional sail shapes are presented with the aerodynamic coefficients for the upwind condition of IMS type sails.…”

“…Two years later, Paton et al [99] investigated the effect of mast rotation on the performance of a sail using a two-dimensional RANS based CFD. In the same year, 2007, Masuyama et al [31] presented the application of a RANS-based CFD method to evaluate the mast influence on aerodynamic forces and flow. This last paper included three-dimensional shapes.…”