The Effect of Forward Speed on Damping for a Variety of Ship Types as Calculated by Thin Ship Theory

摘要

Since the damping coefficients play a predominant role in the motion response of ships in pitch and heave at resonant frequencies in a seaway, use was made of two computer programs recently developed at M. I. T. to calculate, by thin ship theory, the effect of ship speed on the damping coefficients in pitch and heave for four diverse types of ship hulls--cargo ship, tanker, destroyer, and trawler. Results indicate that, for all four hull types, there is a marked increase in pitch damping coefficient and a smaller increase in heave damping coefficients as the ship speed is reduced, when the ship is oscillating at resonant frequency. These results are not substantiated by recent oscillator tests on a ship model, wherein a much less dependency of damping on forward speed is measured. (Author)