The Aerodynamic of the Keel of the America’s Cup Yachts: an Optimization Procedure

Abstract

The aerodynamic of a keel of an America's Cup yacht is quite complex: in fact, the geometry is characterized by a "flapped wing", with a large slender body (the bulb) and two winglets placed at the tip. Therefore, a systematic analysis taking into account the effects of all the parameters appears to be difficult.

In order to tackle this problem resort was made to a direct numerical optimization technique; this approach was attractive, as it made it possible to address the problem systematically, and offered flexibility in the choice of the design variables. This approach is extremely flexible, and capable of meeting multi-disciplinary requirements. The optimization procedure is completely described in the paper.

Because the flow complexity, the aerodynamic solutions require a RANS solver, and FLUENT 6.2.16 was used. For the parametric CAD model, used for the optimization loop, CATIA V5R16 was used, and an automatic procedure for the grid generation was developed by Gambit 2.3.16. The procedure was driven by the multidisciplinary optimization code modeFRONTIER 3.2.

The objective function was a weighted combination of the drag in different conditions, with fixed total lift values. The effect of the centre of gravity position and the maneuvering performance reduction with the bulb length were taken into account, and several constraints were considered.