Design aspects of catamarans operating at high speed in shallow water

Abstract

The thesis describes the investigation into the design aspects of the high-speed displacement catamaran.  This work is presumably an extension of the existing database on the high-speed displacement hull form series namely the NPL series.  The experimental test programme has been extended in the current research to investigate the influence of bulbous bows on the high-speed displacement catamaran performance in deep and shallow water conditions.  Four bulbous bows have been developed by ranging bulbous bow’s projecting length, between 1.25% to 6.25% of the length of waterline.  These bulbous bows have been designed and faired to the parent hull, NPL5b or known as a Model 5b of the NPL Series, whilst the after body and the fore body from amidships to 0.3 Lpp are being kept unchanged.  However, the cross section parameter has been fixed at value 0.303 i.e. the ratio of the bulbous bow cross section area at forward perpendicular to the midship section area.  Measurements of total resistance, wash, trim and sinkage have been made up to a Froude number of unity in deep and shallow waters.  In addition to the calm water tests, these models were also tested in regular waves covering a wavelength to ship length ratio λ/L between 0.5 and 2.0 whilst the wave height was maintained at 0.030 m.  Measurements of added resistance in waves, pitch, hence and wash cuts were made.  The thin ship theory computer codes namely wave13d.for and wave3d3ss.for have been used to validate the measured wash cuts.</p