A proper design of the mooring systems for Wave Energy Converters (WECs) requires an accurate investigation of both operating and extreme wave conditions. A careful analysis of these systems is required to design a mooring configuration that ensures station keeping, reliability, maintainability, and low costs, without affecting the WEC dynamics. In this context, an experimental campaign on a 1:20 scaled prototype of the ISWEC (Inertial Sea Wave Energy Converter), focusing on the influence of the mooring layout on loads in extreme wave conditions, is presented and discussed. Two mooring configurations composed of multiple slack catenaries with sub-surface buoys, with or without clump-weights, have been designed and investigated experimentally. Tests in regular, irregular, and extreme waves for a moored model of the ISWEC device have been performed at the University of Naples Federico II. The aim is to identify a mooring solution that could guarantee both correct operation of the device and load carrying in extreme sea conditions. Pitch motion and loads in the rotational joint have been considered as indicators of the device hydrodynamic behavior and mooring configuration impact on the WEC.

Planing hard chine hull forms are widely used for high-speed small craft. While monohedral¹ deep V forms have been commonly used for more than 25 years, recent trends are toward non-monohedral forms in which most of the hydrodynamic lift is produced by low deadrise areas in the after part of the hull. The deadrise gradually increases in the centre and forebody, allowing greater angles of incidence that are beneficial to reduce wave impact forces and ship motions. Wetted surface also is reduced in comparison to the standard monohedral form, resulting in smaller frictional resistance. This trend has been initiated by the search for better seakeeping performances, and made possible by a general reduction in ship weight due to higher main engine power/weight ratio and lower structural weight. Resistance predictions based on Savitsky’s method are commonly used, although this procedure has been developed on the hypothesis of monohedral geometry for the wetted part of the hull. The results are consequently affected by errors due to wrong assessment of both hydrodynamic lift and centre of pressure In this paper, two procedures for the application of Savitsky’s method to non-monohedral hulls are proposed. The results relative to a recently developed non-monohedral hull form are compared to those obtained by the standard Savitsky method and by towing tank tests. Furthermore, a study for the analysis of error propagation in Savitsky’s long form procedure is proposed.