Effects of Free Surface Fluctuations on Total Wave Force on Cylinder

Abstract

Past studies have revealed that free surface fluctuation has a profound influence on the wave force of elements of objects close to the still-water level. This study examines the effects of free surface fluctuation on the total wave force on a rigid, fixed, vertical, uniform, circular cylinder of small diameter, protruding above the still-water level. The waves are unidirectional, stationary, zero mean, linear, Gaussian, and narrow banded. Expressions of the mean and standard deviation of the total wave force on the cylinder are derived. The effects of free surface fluctuation on these statistical properties are examined for the full range of water depth. This study shows that free surface fluctuation affects the mean value of total wave force only in relatively shallow water, but the standard deviation of the total wave force can be affected in all water depths if the penetration of the cylinder above the still water level is small.