Trans RINA, Vol 153, Part B2, Intl J Small Craft Tech, 2011 Jul-Dec
and mainsail shapes and rig performance by taking into account separated flows through RANS modelling.
The optimization problem may be formulated as
follows: for a given apparent wind angle, what are the optimal cambers and related trim angles for mainsail and jib which maximize the driving force, Fr, of the complete rig? The apparent wind angle chosen was = 30°.
As in the single sail optimization, the Simplex algorithm has been used. The results for the optimum camber & trim angle are listed in the following table:
Objective (f/c)m* (f/c)f*
Figure 6b: convergence of the sail camber f/c versus the number of explored design
Max(Fr) 27% 30% 3° Max(Fr/Fh) 4% 19%
*m 10°
*f
32° 31°
The solution that maximizes the driving force is visualized in Figure 9. As in the previous case, small separation regions are found near the trailing-edge on the suction surfaces.
Figure 7: convergence of the driving force coefficient Cr versus the number of explored design
Figure 9: stream function around two interacting sails for maximum driving force at = 30°
For further investigation, and more realistic or useful results for a given boat, it will be necessary to extend ADONF to three-dimensional sails optimization and possibly to take into account a constraint on the heeling moment. This constraint may be added through a penalty method or another constraint handling method [37, 42]. The extension to three-dimensional flows and fluid-structure interaction is underway [43] as may be seen in the next sections. Validations of ADONF results on
interacting sails through
Figure 8: streamlines around the sail for maximum driving force at = 30°
7.3 OPTIMAL INTERACTING SAILS A more challenging
wind-tunnel test
comparisons will be useful but are hard to do without experimental results in the open literature.
optimization problem is the
interacting sails problem. The mainsail-jib interaction on a sailing boat is a well known problem which has generated long debates and controversies [1, 41]. The question was to know if ADONF may be useful to explore the sail interaction problem in more detail and contribute to clarifying the relation between foresail
B-110
7.4 3D SAIL DESIGN OPTIMIZATION Our computational
framework ADONF has
been
extended to three-dimensional optimization. As a first example of a three-dimensional
aerodynamic
optimization based on RANS simulations a generic mainsail in upwind conditions is considered.
The sail optimization problem is defined as follows: search to maximize the driving force of the sail through
©2011: The Royal Institution of Naval Architects
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