Reconfiguration and dynamics of clamped fibers under finite-amplitude surface gravity waves

TL;DR

This study uses numerical simulations to analyze how flexible submerged stems respond to finite-amplitude surface gravity waves, revealing different behaviors depending on their natural frequency relative to the wave frequency.

Contribution

It provides new insights into the reconfiguration and dynamics of submerged flexible structures under wave action across a wide range of rigidity.

Findings

Two distinct response regimes based on f_nat/f_wave ratio.

Resonance occurs when f_nat approximately equals f_wave.

Reconfiguration influenced by Stokes drift and natural frequency.

Abstract

We investigate the behaviour of a flexible stem completely submerged under a surface gravity wave of finite amplitude using fully resolved direct numerical simulations. By varying the rigidity of the stem over ten orders of magnitude, we explore its motion in the drag-dominated regime with realistic air and water properties. Our findings reveal two distinct structural responses of the stem depending on the ratio between its natural frequency (f_nat) and the wave frequency (f_wave). For f_nat/f_wave >> 1, the stem maintains on average a straight configuration and exhibits streamwise oscillations in phase-opposition with the wave, moving symmetrically with respect to the vertical direction. Conversely, for f_nat/f_wave << 1, the stem reconfigures under the influence of the Stokes drift, bending forward and breaking the symmetry, and exhibits oscillations that are more coherent with the surrounding flow field. Resonance is observed when f_nat is approximatively f_wave. These results provide new insights into the dynamics of slender vegetation and man-made structures in wave fields, offering valuable implications for marine biology and engineering.