Towed ship motion test in directional spectrum waves in a long tank

Abstract

Recently the techniques of generating short crested waves with arbitrary directional spectrum are developed, and some experiments are conducted in such waves. However, ship towing or running tests in such waves are not conducted yet, because sufficiently uniform experimental area could not be obtained. This paper reports ship motion test in towed condition (Froude numbers are 0.2 and 0.275) in a long tank by generating uniform irregular waves with arbitrary directional spectrum, and describe the comparison between analyzed results and theoretically estimated results. The compared results show relatively good agreement.For this experiment, a snake type wave maker was newly developed and installed at the end of the long tank of Yokohama National University.For the analysis of directional wave spectrum, we adopted so called Maximum Likelyhood Method.Theoretical estimation is made by using analyzed directional wave spectrum as input wave and also by using directional motion transfer functions calculated by so called New Strip Method.