An investigation into the aerodynamic drag on the superstructures of fast catamarans

Molland, A.F. and Barbeau, T.-E. (2003) An investigation into the aerodynamic drag on the superstructures of fast catamarans. Transactions of The Royal Institution of Naval Architects Part A: International Journal of Maritime Engineering, 145, 29-39.

Abstract

An investigation has been carried out into the aerodynamic drag of a family of fast catamaran superstructures and above water hulls travelling in still air, using experimental and theoretical techniques. Based on a number of existing and proposed designs, a family of seven generic superstructure shapes were created for the investigation. Wind tunnel experiments were carried out on models of the superstructures alone and combinations of superstructure and above water hulls. The drag on the superstructure models was measured at zero incidence and 150 incidence in a 0.9m x 0.6m wind tunnel with a groundboard, and drag and vertical lift were measured at zero incidence in a 2.1m x 1.6m wind tunnel with a moving ground. A commercial CFD code (CFX) was used to model the superstructure numerically in two dimensions and the drag results were compared with the experimental values. It was found that the numerical approach broadly reproduced the likely changes in aerodynamic drag due to changes in superstructure shape. The results of the investigation demonstrate that changes in superstructure shape can have important effects on superstructure drag. For each superstructure shape, drag coefficients are presented which should be suitable for practical powering applications. Most of the drag data, particularly for the superstructures alone, are also applicable to monohull vessels.

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