Effects of Forward Speed of a Ship on Added Resistance in Waves

摘要

Despite a large amount of work so far, it is said that the predictionaccuracy in the added resistance is not enough particularlyin a range of short waves. For engineering purposes, applicationof the enhanced unified theory (EUT) seems promising for evaluatingthe wave-amplitude function which is the most importantterm in Maruo's formula for the added resistance. To confirm applicabilityof the EUT, measurements of the wave-induced shipmotions and added resistance are carried out using a modifiedWigley model at several Froude numbers, and obtained resultsare compared with computed ones. Discrepancy in the added resistanceis observed at short wavelengths when the forward speedis present, and the amount of this discrepancy tends to increaseand then become constant as the forward speed increases. Thisdiscrepancy may be attributed to hydrodynamic nonlinear effectsin the wave diffraction at the bow, which may be intensified in thepresence of forward speed. A practical factor for correcting thisdiscrepancy, which is to be applied only to the component due todiffraction of incident wave, is proposed in a form of mathematicalfunction in the Froude number and the ratio of wavelengthto ship length.