Wave-Induced Drift of Large Floating Objects in Regular Waves

Abstract

The current study experimentally investigates the wave-induced drift velocity of two-dimensional large floating objects (with Lg/L>0.2, where Lg = longitudinal length of the floating objects, and L = wavelength) under the action of regular waves. The focus is on the high-precision measurement of drift behavior and a wider range of parameters than what was previously reported in the literature. Stacked wood pieces with various submergences (s) were used to simulate the large floating objects on the water surface. An infrared-based motion monitoring system with two high-resolution cameras continuously recorded their motion in regular waves. The results show that the drift velocity increased quickly from the beginning and reached a quasi-steady mean value. The magnitude of the quasi-steady drift velocity increased with ratio of the pitch period to the wave period (TR/T), until reaching a maximum when TR/T≈1. After that, further increasing the ratio of TR/T did not lead to additional significant changes in the drift velocity. Three nondimensional submergences (s/Lg) of 0.0075, 0.022, and 0.036 were examined. The drift velocity typically decreased with larger submergence, which can be attributed to the larger added mass involved in the oscillatory motion.