A NUMERICAL STUDY ON SURFACE WAVE EVOLUTION OVER VISCOELASTIC MUD

Elham Sharifineyestani,Navid Tahvildari

doi:10.9753/icce.v36.waves.64

Abstract

A numerical modeling approach is applied to investigate the combined effect of wave-current-mud on the evolution of nonlinear waves. A frequency-domain phase-resolving wave-current model that solves nonlinear wave-wave interactions is used to solve wave evolution. A comparison between the results of numerical wave model and the laboratory experiments confirms the accuracy of the numerical model. The model is then applied to consider the effect of mud properties on nonlinear surface wave evolution. It is shown that resonance effect in viscoelastic mud creates a complex frequency-dependent dissipation pattern. In fact, due to the resonance effect, higher surface wave frequencies can experience higher damping rates over viscoelastic mud compared to viscous mud in both permanent form solution and random wave scenarios. Thus, neglecting mud elasticity can result in inaccuracies in estimating total wave energy and wave shape.

Highlights

The interaction among surface waves, currents, and muddy sea beds in coastal waters is complex; it is well known that surface waves are dissipated while propagating over a muddy seabed as a result of wave energy dissipation within the bed (e.g. Gade,1958)
Liu and Chan (2006) studied the small amplitude long wave propagation over a thin viscoelastic mud layer theoretically. They showed that the coupling between mud viscosity and elasticity results in complexities in predicting wave dissipation rate. They found that the wave attenuation rate does not always diminish as the elastic shear modulus increases, and that there is a possible resonance effect when the magnitude of wave frequency becomes closer to the natural frequency of the viscoelastic mud layer
We extend the model of Kaihatu and Tahvildari (2012) which captures wave-current interaction in the presences of viscous mud, by accounting for viscoelastic mud

Summary

Introduction

The interaction among surface waves, currents, and muddy sea beds in coastal waters is complex; it is well known that surface waves are dissipated while propagating over a muddy seabed as a result of wave energy dissipation within the bed (e.g. Gade,1958). Kaihatu and Tahvildari (2012) extended the wave-current interaction model of Kaihatu (2009) to include mud-induced dissipation mechanism of Ng (2000). The model shows that co-propagating currents act to reduce mud-induced wave dissipation while counter propagating flows increase the dissipation. Liu and Chan (2006) studied the small amplitude long wave propagation over a thin viscoelastic mud layer theoretically.

Results

Conclusion