Preferential orientation of slender elastic floaters in gravity waves

TL;DR

This paper develops a hydro-elastic theory to predict the preferential orientation of slender elastic floaters in gravity waves, revealing how their physical properties influence their stable orientations.

Contribution

It introduces a new diffractionless model to compute wave-induced yaw moments and derives criteria for floaters' preferred orientations based on their elasticity and size.

Findings

Short, heavy floaters prefer longitudinal orientation.

Long, light floaters prefer transverse orientation.

Floaters longer than wavelength may have multiple stable orientations.

Abstract

Slender floaters drifting in propagating gravity waves slowly rotate towards a preferential state of orientation with respect to the angle of incidence. This angular drift arises from a wave-induced, second order mean yaw moment. We develop a diffractionless, hydro-elastic theory to compute this mean yaw moment for a thin, flexible structure whose width and thickness are small compared with the wavelength. For floater lengths smaller than half the wavelength, we derive a simple, predictive criterion for the preferred orientation: Soft, short and heavy floaters prefer the longitudinal state, while stiff, long and light floaters prefer the transverse state. For floaters longer than the wavelength, the orientational dynamics become more intricate and may exhibit multiple equilibrium states. We discuss the implications of the model for flexible floating structures such as pontoons and inflatable structures.