A Practical Correction Method for Added Resistance in Waves

Abstract

In order to estimate ship speed in actual seas it is important to calculate added resistance in waves with accuracy. Added resistance in waves usually appends the effect of wave reflection to added resistance due to ship motion. The effect is understood as the correction of the diffraction force in short waves. The conventional formula for the added resistance due to wave reflection was derived for large blunt ships. For fine ships such as a container ship, the estimation of the added resistance in short waves has poor agreement with the experimental result. We propose a practical correction method for added resistance in waves. From the point of accuracy the correction involves a tank test in the estimation of added resistance due to wave reflection. The test is conducted with different ship speed in short waves of a single kind of wave length. The correction method and the comparison with the experiments are presented here. Thereafter the influence on decrease of ship speed in actual seas is evaluated for a large container ship.