EXPERIMENTAL STUDY ON HEAVE AND PITCH MOTION CHARACTERISTICS OF A WAVE-PIERCING TRIMARAN

Dynamic behaviour of a trimaran vessel is investigated in this study. The body of the trimaran is composed of a centre hull with a quite slender wave piercing bow profile (a length-to-width ratio of 12.96) and two outriggers with Wigley mathematical body forms. Several seakeeping tests are conducted on the model of the trimaran vessel in a towing tank in order to study its heave and pitch motions at different Froude numbers of 0.2, 0.37, and 0.51. Generated waves in the towing tank are of regular type with the wave length changing from 0.6 m to 2.4 m by an increment of 0.3 m. Amplitude of the waves is equal to either 25 mm or 35 mm. A resonance peak can be detected on the curve of the heave response amplitude operator (RAO) versus nondimensional wave length of around 1.0. Increasing the Froude number leads to rapidly descending post-resonance-peak regions of the heave RAO-nondimensional wave frequency diagrams. Changes in the value of the pitch RAO versus nondimensional wave lengths of less than 0.8 are not so sensitive to the changes in the values of Froude number and wave amplitude. Also, for the values greater than 2.5 to 2.8 of the nondimensional wave frequency, the pitch RAO does not experience any significant changes as a result of variations in the Froude number or wave amplitude.