速力制御による燃料節約…IV : 海流と汚損の影響

概要

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In planning a sailing schedule to minimize fuel consumption of a ship, we must estimate currents, the effects of fouling, winds and waves. One of the good ways for this purpose is to analyse the abstract logbook of a ship running the same route many times. Ship speed over ground V_0 is affected by many factors. We assume the following equation concerning to the mean value of a one-way voyage. V_0=V±S+C(d-d^^^)+D(h-h^^^) S=S^^^+Asinωt+Bcosωt where V: ship speed through water, S^^^: yearly mean of ocean current, A, B: amplitudes of seasonal change of the current, C: coef. for fouling, D: coef. for winds and waves, t: days after beginning of a year, d: days after docking, h: hours when strong winds (Beaufort scale above 6) are blowing, + sign for homeward, - sign for outward voyage. Abstract logbooks from three tankers sailing between Japan-Persian Gulf are analysed. Then, A: negligible, B≒-0.3' fouling effect is 0.4'〜1.3' speed down per year, and strong wind effect is 1.3'〜2.2' speed down. The anual mean S^^^≒0.1' is estimated from current chart. The root mean square of residuals of experimental equations are reduced to half when these values are applied to the fuel consumption F=KV^a△^b.
1984-09-25