Abstract
The average increase in power in waves over that in still water has been determined by calculating added torque and added RPM for a 71,000 deadweight ton tanker on the Persian Gulf to Northern Europe trade route via the Cape of Good Hope. Responses to irregular short-crested multi-directional waves were computed from model tests in regular waves at all headings, based on the linear super-position technique. A family of sea spectra described by the ISSC formulation was used and the occurrence of the spectra on the specified route was determined from the statistical data of Hogben and Lumb. The predicted added power for this trade route was very modest, ranging downward from 12.6% of the still water power at low speed to only 1.3% at high speed. The effects of wind, currents, fouling, and voluntary slowdowns are not included. The technique is applicable to any ship, any type of response, and any trade route adequately described by the ocean wave statistics.
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