Experimental investigation of a fast catamaran in head waves

Abstract

The present work is about the seakeeping behavior of a fast catamaran advancing in head sea. To this aim seakeeping tests with transient, regular and irregular waves are performed in the rectilinear water tank of CNR-INSEAN. Seakeeping transient tests are used to provide the response amplitude operator for a wide range of wave lengths and several speeds of advancement. These tests allow identifying the Froude number at which the maximum vertical response occurs and an analysis of natural heave and pitch frequencies. A comparison with theoretical predictions is provided. Regular wave tests are used to assess nonlinear effects on the hull motions, as well as the added resistance generated by the increasing steepness and dependency on both the Froude number and wave lengths: therefore several ship speeds, several steepness and wave lengths of the incident wave system are considered. For a similar Froude number range, irregular wave tests are also pursued to investigate the seakeeping properties of the vessel in real scenarios. The estimation of added resistance in wave, its dependency on the Froude number, the investigation of nonlinear effects and the analysis of increased resistance in a real scenario are addressed as well. To make sure the present experimental campaign is valid, it is checked with repeatability analysis and matched with ad hoc experimental data collected at TU Delft. The whole set of measurements is a valuable database for both hydrodynamic studies of high speed catamarans and CFD validation.