Experimental investigation of interference effects for high-speed catamarans

• EFD activities are used to study the hydrodynamic properties of a catamaran.
• Calm water tests are performed for a range of speeds and separation distances.
• Wave pattern measurements have been acquired in the inner and outer region.
• We highlighted the presence of two humps in the total resistance coefficient curve.
• Humps in the resistance coefficient curve are correlated to attitude and wave pattern.

We have performed an experimental investigation aimed at assessing the relevance of hull interference effects on the total resistance of a catamaran model advancing in calm water. To this purpose, drag and attitude measurements have been carried out for several values of the hull separation, as well as for the monohull, at changing the Froude number in the range 0.1–0.8. Data concerning the two-dimensional wave field around the models have also been collected. Our results indicate that, except for a narrow range of conditions where favorable interference is observed, the interaction between the catamaran hulls usually results in a marked increase of the total resistance as compared to the monohull case. This penalization can be as large as 30% for the narrowest hull spacing at Fr≈0.5Fr≈0.5. At larger hull spacings, the effect is attenuated and occurs at smaller Froude numbers. Interference effects are less evident both in the small and large Froude number range, namely when Fr<0.3Fr<0.3 and Fr>0.7Fr>0.7 respectively. Insight into the mechanisms underlying this behavior is obtained by examining the relational dependence between the resistance variation and the data concerning attitude of the vessel and wave-field elevation.