まき網漁船(116トン型)の動揺について-II : 横動揺の計算値と実測値の比較

Abstract

It is well known that if we obtain the wave spectrum in a suitable form and the theoretical response characteristics of the ship to the regular waves, it is possible to compute the spectrum of ship motions. In this report, the author calculated the ship rolling motion in irregular waves and compared it with the measured motion. The wave spectrum applied in this calculation were obtained using the Pierson-Moskowitz wave spectrum for the not fully arisen wave, and assumed that the wave spectrum have maximum energy at the natural frequency of the ships rolling. Basic equation for the rolling motion is shown in formula (1). The calculated spectra obtained in this way are compared in Fig. (3) with spectra computed from the actual rolling motion which was measured during the trials at a speed of 8kts on three headings to the dominant wave direction. The statistical values of ship rolling calculated using the calculated roll spectra, are compared with measured values in Figs. (5)〜(6). The agreement between calculated and measured results is reasonable good, although the theory tends to under-estimate the motion in bow waves and to over-estimate it in quartering waves.